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Blue Whale - Balaenoptera musculus
California blue whales rebound from whaling; first of their kin to do so

Date: September 5, 2014
Source: University of Washington

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California blue whales -- the cow is 76 feet long and the calf is 47 feet -- swim near the California Channel Islands.

The number of California blue whales has rebounded to near historical levels, according to new research by the University of Washington, and while the number of blue whales struck by ships is likely above allowable U.S. limits, such strikes do not immediately threaten that recovery.
This is the only population of blue whales known to have recovered from whaling -- blue whales as a species having been hunted nearly to extinction. Blue whales -- nearly 100 feet in length and weighing 190 tons as adults -- are the largest animals on earth. And they are the heaviest ever, weighing more than twice as much as the largest known dinosaur, the Argentinosaurus. They are an icon of the conservation movement and many people want to minimize harm to them, according to Trevor Branch, UW assistant professor of aquatic and fishery sciences.
"The recovery of California blue whales from whaling demonstrates the ability of blue whale populations to rebuild under careful management and conservation measures," said Cole Monnahan, a UW doctoral student in quantitative ecology and resource management and lead author of a paper on the subject posted online Sept. 5 by the journal Marine Mammal Science. Branch and André Punt, a UW professor of aquatic and fisheries sciences, are co-authors.
California blue whales are at their most visible while at feeding grounds 20 to 30 miles off the California coast, but are actually found along the eastern side of the Pacific Ocean from the equator up into the Gulf of Alaska.
Today they number about 2,200, according to monitoring by other research groups. That's likely 97 percent of the historical level according to the model the co-authors used. That may seem to some a surprisingly low number of whales, Monnahan said, but not when considering how many California blue whales were caught. According to new data Monnahan, Branch and another set of co-authors published earlier this summer in PLOS ONE, approximately 3,400 California blue whales were caught between 1905 and 1971.
"Considering the 3,400 caught in comparison to the 346,000 caught near Antarctica gives an idea how much smaller the population of California blue whales was likely to have been," Branch said.
The catches of blue whales from the North Pacific were unknown until scientists -- in particular Yulia Ivashchenko of Southern Cross University in Australia -- put on their detective caps and teased out numbers from Russian whaling archives that once were classified as secret but are now public. The numbers Russian whalers had publicly reported at one time were incomplete and inaccurate ¬- something that was admitted in the late 1990s -- but there wasn't access to the real numbers until recently.
For the work published in PLOS ONE, the scientists then used acoustic calls produced by the whales to separate -- for the first time -- the catches taken from the California population from those whales taken in the western Northern Pacific near Japan and Russia. The two populations are generally accepted by the scientific community as being different. Places where acoustic data indicated one group or the other is present were matched with whaling catches.
In the subsequent Marine Mammal Science paper just out, the catches were among the key pieces of information used to model the size of the California blue whale population over time -- a model previously used by other groups to estimate populations of hundreds of fish and various other whale species.
The population returning to near its historical level explains the slowdown in population growth, noted in recent years, better than the idea of ship strikes, the scientists said.
There are likely at least 11 blue whales struck a year along the U.S. West Coast, other groups have determined, which is above the "potential biological removal" of 3.1 whales per year allowed by the U.S. Marine Mammal Protection Act. The new findings says there could be an 11-fold increase in vessels before there is a 50 percent chance that the population will drop below what is considered "depleted" by regulators.
"Even accepting our results that the current level of ship strikes is not going to cause overall population declines, there is still going to be ongoing concern that we don't want these whales killed by ships," Branch said.
Without ship strikes as a big factor holding the population back -- and no other readily apparent human-caused reason (although noise, chemical pollution and interactions with fisheries may impact them) -- it is even more likely that the population is growing more slowly because whale numbers are reaching the habitat limit, something called the carrying capacity.
"We think the California population has reached the capacity of what the system can take as far as blue whales," Branch said.
"Our findings aren't meant to deprive California blue whales of protections that they need going forward," Monnahan said. "California blue whales are recovering because we took actions to stop catches and start monitoring. If we hadn't, the population might have been pushed to near extinction -- an unfortunate fate suffered by other blue whale populations."
"It's a conservation success story," Monnahan said.
Funding for students working on the research in Branch's lab comes through the Joint Institute for the Study of the Atmosphere and Ocean, a collaboration between the National Oceanic and Atmospheric Administration and UW.

Journal References:
Cole C. Monnahan, Trevor A. Branch, Kathleen M. Stafford, Yulia V. Ivashchenko, Erin M. Oleson. Estimating Historical Eastern North Pacific Blue Whale Catches Using Spatial Calling Patterns. PLoS ONE, 2014; 9 (6): e98974 DOI: 10.1371/journal.pone.0098974

Blue whales (Balaenoptera musculus) were exploited extensively around the world and remain endangered. In the North Pacific their population structure is unclear and current status unknown, with the exception of a well-studied eastern North Pacific (ENP) population. Despite existing abundance estimates for the ENP population, it is difficult to estimate pre-exploitation abundance levels and gauge their recovery because historical catches of the ENP population are difficult to separate from catches of other populations in the North Pacific. We collated previously unreported Soviet catches and combined these with known catches to form the most current estimates of North Pacific blue whale catches. We split these conflated catches using recorded acoustic calls from throughout the North Pacific, the knowledge that the ENP population produces a different call than blue whales in the western North Pacific (WNP). The catches were split by estimating spatiotemporal occurrence of blue whales with generalized additive models fitted to acoustic call patterns, which predict the probability a catch belonged to the ENP population based on the proportion of calls of each population recorded by latitude, longitude, and month. When applied to the conflated historical catches, which totaled 9,773, we estimate that ENP blue whale catches totaled 3,411 (95% range 2,593 to 4,114) from 1905–1971, and amounted to 35% (95% range 27% to 42%) of all catches in the North Pacific. Thus most catches in the North Pacific were for WNP blue whales, totaling 6,362 (95% range 5,659 to 7,180). The uncertainty in the acoustic data influence the results substantially more than uncertainty in catch locations and dates, but the results are fairly insensitive to the ecological assumptions made in the analysis. The results of this study provide information for future studies investigating the recovery of these populations and the impact of continuing and future sources of anthropogenic mortality.

Cole C. Monnahan, Trevor A. Branch, André E. Punt. Do ship strikes threaten the recovery of endangered eastern North Pacific blue whales? Marine Mammal Science, 2014; DOI: 10.1111/mms.12157

Blue whales were targeted in the North Pacific from 1905–1971 and are listed as endangered by the IUCN. Despite decades without whaling, abundance estimates for eastern North Pacific (ENP) blue whales (Balaenoptera musculus) suggest little evidence for a recent increase. One possible reason is fatal strikes by large ships, which have affected populations of other cetaceans and resulted in mitigation. We used a population dynamics model to assess the trends and status of ENP blue whales, and the effects of ship strikes. We estimate the population likely never dropped below 460 individuals, and is at 97% of carrying capacity (95% interval 62%–99%). These results suggest density dependence, not ship strikes, is the key reason for the observed lack of increase. We also estimate future strikes will likely have a minimal impact; for example, an 11-fold increase in vessels would lead to a 50% chance the long-term population would be considered depleted. Although we estimate ship strike mitigation would have minimal impacts on population trends and status, current levels of ship strikes are likely above legal limits set by the U.S. The recovery of ENP blue whales from whaling demonstrates the ability of blue whale populations to rebuild under careful management.;jsessionid=34D76EE7CB4DE42835ADEAF5B99C626D.f03t01
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  • Claudiu Constantin Nicolaescu
Study on world's biggest animal finds more than one population in the southeastern Pacific

Date: December 18, 2014
Source: Wildlife Conservation Society
Scientists are examining molecular clues to answer a big question: how many types of blue whales exist in the waters of the southeastern Pacific?

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A blue whale swimming through the waters of coastal southern Chile, the location of a feeding and nursing ground for the species. Using genetic information, scientists from the Wildlife Conservation Society, the Universidad Austral de Chile, the Blue Whale Center, the American Museum of Natural History (AMNH), and NOAA are working to determine how many types of blue whale exist in the waters of the southeastern Pacific.

Scientists from WCS (Wildlife Conservation Society), the Universidad Austral de Chile, the Blue Whale Center, the American Museum of Natural History (AMNH), NOAA, and other organizations are examining molecular clues to answer a big question: how many types of blue whales exist in the waters of the southeastern Pacific?
The answer seems to be two distinct populations, according to a genetic study comparing the blue whales off the southern coast of Chile with those swimming in the waters of Antarctica and other nearby regions. One of the populations could be made up of pygmy-type blue whales, a subspecies slightly smaller than the Antarctic blue whale. The findings could help wildlife managers devise more effective conservation plans for this endangered species.
The study appears in the online edition of the journal Molecular Ecology.
Reaching nearly 100 feet in length, the blue whale is thought to be the largest animal that ever existed, even larger than the biggest known dinosaurs. Blue whales were nearly hunted to extinction by commercial whaling fleets in the 20th Century before the species was granted international protection in 1966.
Although whaling records dating back to the 1960s indicate that both Antarctic and pygmy-type blue whales utilized Chilean waters, it wasn't until 2004--when a blue whale feeding and nursing ground was discovered in the protected bays of southern Chile--that scientists began to question whether multiple populations of blue whales currently utilized the southeastern Pacific. A previous study had even recognized the existence of an as-of-yet unnamed subspecies of blue whale based on size differences in animals in the southeastern Pacific. At the time, however, it was unknown how closely related the whales on this Chilean feeding ground were to those in other areas, and thus what this discovery might mean in terms of the recovery of the animals in the Southern Hemisphere.
"The most effective way to protect the region's blue whales depends on a better understanding of how blue whales in the waters of Chile interact with other populations of the same species, as well as knowing which areas are used for activities such as feeding and breeding to facilitate future designation of MPA network," said Dr. Juan Pablo Torres-Florez, researcher for the Universidad Austral de Chile and lead author of the study.
"Molecular methods give us the means for uncovering the hidden relationships of blue whales in southeastern Pacific, as well as finding regions of importance to the species," said Dr. Howard Rosenbaum, one of the senior authors of the paper and Director of WCS's Ocean Giants Program.
In order to investigate the genetic identity of blue whales in the coastal waters of southern Chile with respect to blue whales in other areas, the research team sequenced the DNA of 60 animals using skin samples collected from living animals with non-lethal biopsy darts fired from crossbows between 2003 and 2009. The analysis enabled the team to identify 52 individuals based on specific regions of both nuclear and mitochondrial DNA.
The samples from these whales were then compared with existing datasets from whales in the eastern tropical Pacific (where southern Chile blue whales are thought to breed), northern coastal Chile, and Antarctica. The research team found that blue whales in southern Chile are similar in genetic makeup to whales in the eastern tropical Pacific and northern Chile. Whales in Antarctica were deemed to be more distantly related, indicating the region may have two distinct populations or types of blue whales, an important consideration for any plan to protect a wide-ranging marine mammal species in coastal and international waters.
"Our study gives us crucial insights into the population structure of blue whales in the waters of Chile and will serve as an important stepping stone for further research," added Rosenbaum. "The long-term goal of such work would be a network of marine protected areas designed to save the world's largest animal."
The first stepping stone was already been achieved earlier this year with the declaration of Tic Toc Marine Protected Area in the Gulf of Corcovado, Chile. "It's been 10 years since we made the initial discovery of this magnificent blue whale feeding ground with the aid of the WCS and other institutions," said Dr. Rodrigo Hucke-Gaete, principal investigator and professor at Universidad Austral de Chile, as well as president of the Blue Whale Center. He added that "building the puzzle through the aid of scientific evidence has been exciting and has taken time, but is providing robust information to aid in the recovery of this wonderful and still endangered species."

Journal Reference:
J. P. Torres-Florez, R. Hucke-Gaete, R. LeDuc, A. Lang, B. Taylor, L. E. Pimper, L. Bedriñana-Romano, H. C. Rosenbaum, C. C. Figueroa. Blue whale population structure along the eastern South Pacific Ocean: evidence of more than one population. Molecular Ecology, 2014; DOI: 10.1111/mec.12990

Blue whales (Balaenoptera musculus) were among the most intensively exploited species of whales in the world. As a consequence of this intense exploitation, blue whale sightings off the coast of Chile were uncommon by the end of the 20th century. In 2004, a feeding and nursing ground was reported in southern Chile (SCh). With the aim to investigate the genetic identity and relationship of these Chilean blue whales to those in other Southern Hemisphere areas, 60 biopsy samples were collected from blue whales in SCh between 2003 and 2009. These samples were genotyped at seven microsatellite loci and the mitochondrial control region was sequenced, allowing us to identify 52 individuals. To investigate the genetic identity of this suspected remnant population, we compared these 52 individuals to blue whales from Antarctica (ANT, n = 96), Northern Chile (NCh, n = 19) and the eastern tropical Pacific (ETP, n = 31). No significant differentiation in haplotype frequencies (mtDNA) or among genotypes (nDNA) was found between SCh, NCh and ETP, while significant differences were found between those three areas and Antarctica for both the mitochondrial and microsatellite analyses. Our results suggest at least two breeding population units or subspecies exist, which is also supported by other lines of evidence such as morphometrics and acoustics. The lack of differences detected between SCh/NCh/ETP areas supports the hypothesis that eastern South Pacific blue whales are using the ETP area as a possible breeding area. Considering the small population sizes previously reported for the SCh area, additional conservation measures and monitoring of this population should be developed and prioritized.;jsessionid=7DE4DDC4447DDBFC677CA09E4722D2BD.f03t02?systemMessage=Wiley+Online+Library+will+be+disrupted+on+20th+Dec+from+10%3A00-14%3A00+GMT+%2805%3A00-09%3A00+EST%29+for+essential+maintenance.
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  • Claudiu Constantin Nicolaescu
Hunting not to blame for pygmy blue whales' tiny gene pool

Wednesday, 6 May 2015
Anna Salleh

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pygmy blue whales

Australian pygmy blue whales have low genetic diversity because of past climate changes rather than whaling, a new study suggests.

The research, published today in the journal Biology Letters, finds that the whales evolved from a small 'founder' group of Antarctic blue whales that ventured north just 20,000 years ago during the peak of the last glacial period.

"So there's low genetic diversity because they're such a young population and not enough time has passed for them to build up genetic diversity," says Dr Catherine Attard of Flinders University.

"I think it's a hopeful story because it means their low genetic diversity isn't being caused by humans ... It's a natural thing."

The blue whale is the world's largest animal, of which the Antarctic and pygmy blue whales are both subspecies.

While Antarctic blue whales feed around the frozen continent, pygmy blue whales feed in temperate waters, and both migrate towards the equator to breed.

Numbers of blue whales were cut drastically in the 20th century due to whaling, and the now-endangered Australian population of pygmy blue whales has the lowest recorded diversity of blue whales in the world.

Attard and colleagues wanted to know whether this low genetic diversity was due to whaling or natural causes.

They looked at the pattern of genetic mutations in DNA taken from pygmy blue whales in Australia and calculated that, at a given mutation rate, the Australian population evolved from just a few individuals.

The researchers then compared the pygmy blue whale DNA with that of blue whales from elsewhere in the world and this told them that the pygmy blue whale most likely evolved from the Antarctic blue whale.

Climatic change

Interestingly, the Earth was at the peak of a glaciation 20,000 years ago.

"You would have had a lot more ice around Antarctica and so Antarctic blue whales, which feed in Antarctica, would have been pushed more north," says Attard.

"So it seems that some of those Antarctic blue whales ended up going to Australia during this climate change event and they ended up staying there.

"Then, when we moved into the current interglacial period where it's warmer, these whales stayed feeding around Australia and evolved into a different population and a different subspecies."

"They've been around for 20,000 years with a low genetic diversity," says Attard, "and there's no evidence that whaling has reduced their genetic diversity."

She says the findings are good news because it means the pygmy blue whales' low genetic diversity is not the product of inbreeding due to a sudden drop in numbers.

Rather, it is just because they are a relatively young species.

"Twenty thousand years sounds like a long time but it's actually not in terms of an evolutionary timescale," says Attard.

She says in order to recover the pygmy blue whale population to pre-whaling numbers, it will be important to focus on threats such as marine pollution, and marine noise from offshore oil and gas activity that can disturb the whales' communication systems.

Low genetic diversity in pygmy blue whales is due to climate-induced diversification rather than anthropogenic impacts

Catherine R. M. Attard, Luciano B. Beheregaray, K. Curt S. Jenner, Peter C. Gill, Micheline-Nicole M. Jenner, Margaret G. Morrice, Peter R. Teske, Luciana M. Möller
DOI: 10.1098/rsbl.2014.1037 Published 6 May 2015

Unusually low genetic diversity can be a warning of an urgent need to mitigate causative anthropogenic activities. However, current low levels of genetic diversity in a population could also be due to natural historical events, including recent evolutionary divergence, or long-term persistence at a small population size. Here, we determine whether the relatively low genetic diversity of pygmy blue whales (Balaenoptera musculus brevicauda) in Australia is due to natural causes or overexploitation. We apply recently developed analytical approaches in the largest genetic dataset ever compiled to study blue whales (297 samples collected after whaling and representing lineages from Australia, Antarctica and Chile). We find that low levels of genetic diversity in Australia are due to a natural founder event from Antarctic blue whales (Balaenoptera musculus intermedia) that occurred around the Last Glacial Maximum, followed by evolutionary divergence. Historical climate change has therefore driven the evolution of blue whales into genetically, phenotypically and behaviourally distinct lineages that will likely be influenced by future climate change.
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  • Claudiu Constantin Nicolaescu
Epic journey by blue whale
First link to breeding ground for Chilean blue whales

Date: June 11, 2015
Source: Wildlife Conservation Society
Scientists studying blue whales in the waters of Chile through DNA profiling and photo-identification may have solved the mystery of where these huge animals go to breed, as revealed by a single female blue whale named "Isabela."

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Isabela's dorsal fin. Image taken in Chile's Gulf of Corcovado in 2006.

Scientists studying blue whales in the waters of Chile through DNA profiling and photo-identification may have solved the mystery of where these huge animals go to breed, as revealed by a single female blue whale named "Isabela," according to a recent study by the Chile's Blue Whale Center/Universidad Austral de Chile, NOAA and the Wildlife Conservation Society.

The researchers have discovered that Isabela -- a female animal named after the lead author's daughter and a major Galapagos Island of the same name -- has traveled at least once between Chile's Gulf of Corcovado and the equatorial waters of the Galapagos Islands, a location more than 5,000 kilometers away and now thought to be a possible blue whale breeding ground. The journey represents the largest north-south migratory movement ever recorded for a Southern Hemisphere blue whale.

The study titled "First documented migratory destination for Eastern South Pacific blue whales" appears today in the online version of the journal Marine Mammal Science.

"Efforts to protect blue whales and other ocean-going species will always fall short without full knowledge of a species' migratory range. Moreover, with this kind of findings we encourage eastern south Pacific governments to think about the creation of a marine protected areas network for the conservation of this and other migratory species" said lead author Juan Pablo Torres-Florez of the Universidad Austral de Chile and the Blue Whale Center. "Isabela points us in the right direction for further research."

"The discovery emphasizes the benefits of collaboration between scientists and research organizations from different countries," said Paula Olson of Southwest Fisheries Science Center.

"The discovery of Isabela traveling between southern Chile and the waters of Ecuador is important and very timely as we work to promote the recovery of the largest species to ever inhabit the earth," said Dr. Howard Rosenbaum of WCS's Ocean Giants Program. "The movement of this one whale provides important information that will enable us to look further at these important areas for blue whales with goal to ensure their long-term protection."

It is unknown how old Isabela is, or if she has produced any young, but she is at least 82 feet in length and may weigh up to 100 tons.

Seeking to establish links between populations of blue whales in the Gulf of Corcovado and other regions, the researchers examined DNA collected from the skin of blue whales with biopsy darts fired from crossbows across the eastern South Pacific. The team also used data from recorded sightings and photographs in their attempt to connect individual animals to different locations.

The analysis produced a genetic match between a female whale observed and sampled off the coast of southern Chile in the Austral summer of 2006; it turned out the same whale sampled the waters of the Galapagos eight years earlier by NOAA scientists. The team then found that photographs taken of both whales revealed the same distinctively curved dorsal fin and blotchy blue-gray patterns on the back, confirming that both whales were in fact the same animal.

The authors note that blue whales are frequently observed in equatorial Pacific just west of the Galapagos and that a more detailed study might confirm the location as a wintering and breeding ground for at least some of the blue whales of southern Chile.

Reaching nearly 100 feet in length, the blue whale is thought to be the largest animal that ever existed. Blue whales were nearly hunted to extinction by commercial whaling fleets before receiving international protection in 1966. A blue whale calf can measure between 23 and 27 feet in length at birth and weigh almost 3 metric tons.

Story Source: Wildlife Conservation Society. "Epic journey by blue whale: First link to breeding ground for Chilean blue whales." ScienceDaily. (accessed June 12, 2015).

Journal Reference:
Juan Pablo Torres-Florez, Paula A. Olson, Luis Bedriñana-Romano, Howard Rosenbaum, Jorge Ruiz, Richard Leduc Androdrigo Hucke-Gaete. First documented migratory destination for eastern South Pacific blue whales. Marine Mammal Science, 2015 DOI: 10.1111/mms.12239
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  • Claudiu Constantin Nicolaescu
Blue and fin whale distribution in waters off Southern California

Date: June 25, 2015
Source: University of California - San Diego
A new study indicates a steady population trend for blue whales and an upward population trend for fin whales in Southern California.

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A fin whale off Southern California.

A new study led by researchers at Scripps Institution of Oceanography at UC San Diego indicates a steady population trend for blue whales and an upward population trend for fin whales in Southern California.

Scripps marine acoustician Ana Širović and her colleagues in the Marine Bioacoustics Lab and Scripps Whale Acoustic Lab intermittently deployed 16 High-frequency Acoustic Recording Packages (HARPs)--devices that sit on the seafloor with a suspended hydrophone (an underwater microphone)--to collect acoustic data on whales off Southern California from 2006-2012.

Blue and fin whales are common inhabitants of the Southern California Bight, the curved region of California coastline with offshore waters extending from San Diego to Point Conception (near Santa Barbara, Calif.), but little is known about their use of the area.

As described in the June 24 issue of the journal Endangered Species Research, Širović and her colleagues analyzed seven years of acoustic data (26 instrument-years) to study the call abundance of blue and fin whales in the Southern California Bight. The study, largely supported by the Office of Naval Research, provides the first detailed view into the spatial use of Southern California waters by blue and fin whales, the two largest cetacean species in the world. Both are classified as endangered species.

Širović found that blue whale calls were more commonly detected at coastal sites and near the northern Channel Islands, while fin whale calls were detected further off shore, in central and southern areas.

The acoustic data indicate that the blue whale population in Southern California is relatively steady, while the fin whale population is increasing.

"I think it's an interesting difference in trends because both of the species were subject to whaling earlier in the twentieth century, and now they're clearly responding differently," said Širović, assistant researcher in the Marine Physical Laboratory at Scripps.

The acoustic data and overall trends outlined in this study are consistent with another Scripps-led study, but one that used visual data collected from 2012-2013 in the same area as part of the California Cooperative Oceanic Fisheries Investigations (CalCOFI). CalCOFI is a unique partnership led by the California Department of Fish & Wildlife, NOAA Fisheries Service, and Scripps Institution of Oceanography, and it is considered to be one of the world's most valuable marine observation programs.

Published in 2014, the Scripps research conducted through CalCOFI indicated that the blue whale population was relatively steady, while the fin whale population was increasing.

Širović cites the parallel findings between the two studies as evidence that passive acoustics can be used as a powerful tool to monitor population trends for these large marine mammals.

"I think it's very exciting that we see the same trends in the visual and acoustic data, because it indicates the possibility of using acoustics to monitor long-term trends and changes," said Širović.

Presence of a resident fin whale population in Southern California was previously suggested, and the recent study's detection of fin whale calls year-round further supports this idea.

Researchers also found that blue whale calls in the region were generally detected between June and January, evidence that supports the known seasonal migration pattern of blue whales, which tend to migrate from off the coast Mexico (or even as far down as Costa Rica) to Southern California in the late spring. The whales forage through the fall, and then leave in early winter, but researchers aren't certain where they go next.

Although researchers have studied blue and fin whales for years, Širović notes that both species are particularly mysterious, and scientists still don't know some basic information about them, such as their mating system or breeding grounds.

The Southern California Bight is a highly productive ecological territory for many marine animals due to strong upwellings, but researchers have not found any evidence that blue or fin whales are breeding there.

The productivity of the coastal region also makes it a hotbed for human activity, with large cities onshore and ships, commercial fishing vessels, and other human impacts ever-present in the water. Since fin whales generally live further offshore, Širović posits that they might have a slight advantage over blue whales, which tend to inhabit areas where there is more ship traffic--increasing their chances for ship strikes.

"It seems that for fin whales, things are probably improving," said Širović, noting that more research is needed to determine why the blue whale population is not increasing.

"For blue whales, it's a little bit harder to tell. There is a question right now as to whether their population has grown to its maximum capacity, because there are many lines of evidence showing that their population is not growing currently," said Širović. "So the question remains, is it because that's just what their population size can be maximally, or are there factors that are keeping them from growing further?"

Širović hopes that future studies can help identify why there is this difference in population trends of blue and fin whales. Now that she and her colleagues have taken a first look at the broad trends of the two species, they want to dig deeper and look into environmental drivers and other factors and features that may be causing some of the spatial distribution patterns and long-term changes of the whales.

Coauthors of the study included Ally Rice, Emily Chou, John Hildebrand, and Sean Wiggins of Scripps Institution of Oceanography, and Marie Roch of San Diego State University.

The analysis portion of this study was supported by the Office of Naval Research, with data collection and monitoring funded by Chief of Naval Operations N45 and the U.S. Pacific Fleet.

Story Source: University of California - San Diego. "Blue and fin whale distribution in waters off Southern California." ScienceDaily. (accessed June 26, 2015).

Journal Reference:
A Širovic, A Rice, E Chou, JA Hildebrand, SM Wiggins, MA Roch. Seven years of blue and fin whale call abundance in the Southern California Bight. Endangered Species Research, 2015; 28 (1): 61 DOI: 10.3354/esr00676

ABSTRACT: Blue whales Balaenoptera musculus and fin whales B. physalus are common inhabitants of the Southern California Bight (SCB), but little is known about the spatial and temporal variability of their use of this area. To study their distribution in the SCB, high-frequency acoustic recording packages were intermittently deployed at 16 locations across the SCB from 2006 to 2012. Presence of blue whale B calls and fin whale 20 Hz calls was determined using 2 types of automatic detection methods, i.e. spectrogram correlation and acoustic energy detection, respectively. Blue whale B calls were generally detected between June and January, with a peak in September, with an overall total of over 3 million detections. Fin whale 20 Hz calls, measured via the fin whale call index, were present year-round, with the highest values between September and December, with a peak in November. Blue whale calls were more common at coastal sites and near the northern Channel Islands, while the fin whale call index was highest in the central and southern areas of the SCB, indicating a possible difference in habitat preferences of the 2 species in this area. Across years, a peak in blue whale call detections occurred in 2008, with minima in 2006 and 2007, but there was no long-term trend. There was an increase in the fin whale call index during this period. These trends are consistent with visual survey estimates for both species in Southern California, providing evidence that passive acoustics can be a powerful tool to monitor population trends for these endangered species.
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  • Claudiu Constantin Nicolaescu
To breathe or to eat: Blue whales forage efficiently to maintain massive body size
Blue whale feeding strategy targets highest-quality prey, maximizing energy gain

Date: October 2, 2015
Source: NOAA Fisheries West Coast Region
As the largest animals to have ever lived on Earth, blue whales maintain their enormous body size through efficient foraging strategies that optimize the energy they gain from the krill they eat, while also conserving oxygen when diving and holding their breath, a new study has found.

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Ari Friedlaender of Oregon State University tags a blue whale. Image collected under NOAA Fisheries permit.
Credit: Jeremy Goldbogen

As the largest animals to have ever lived on Earth, blue whales maintain their enormous body size through efficient foraging strategies that optimize the energy they gain from the krill they eat, while also conserving oxygen when diving and holding their breath, a new study has found.

Large, filter-feeding whales have long been thought of as indiscriminate grazers that gradually consume copious amounts of tiny krill throughout the day -- regardless of how prey is distributed in the ocean. But tagged blue whales in the new study revealed sophisticated foraging behavior that targets the densest, highest-quality pretty, maximizing their energy gain.

Understanding blue whale feeding behavior will help inform protections for the endangered species and its recovery needs, the scientists say. The study, by researchers from NOAA Fisheries, Oregon State University and Stanford University, was published this week in Science Advances.

"For blue whales, one of our main questions has been: How do they eat efficiently to support that massive body size," said Elliott Hazen, a research ecologist with NOAA Fisheries' Southwest Fisheries Science Center and lead author of the research. "Now we know that optimizing their feeding behavior is another specialization that makes the most of the food available."

Adult blue whales can grow to the length of a basketball court and weigh as much as 25 large elephants combined, but they operate on an "energetic knife-edge," the researchers point out. They feed through the extreme mechanism of engulfing as much prey-laden water as they weigh and then filtering out the tiny krill it contains.

But feeding expends tremendous amounts of energy and the dense krill patches they need to replenish that energy are often deep and difficult to find.

In their study, the researchers compared the foraging of 14 tagged blue whales to 41 previously tagged blue whales off the coast of California, combining the data with acoustic surveys that measured the density of their sole prey, krill -- tiny (less than one inch) crustaceans found throughout the world's oceans.

The researchers found that when the krill were spread out, or less dense, blue whales fed infrequently to conserve their oxygen and energy use for future dives. When krill density increased, they began "lunge-feeding" more frequently, consuming more per dive to obtain as much energy from the krill as possible.

"Blue whales don't live in a world of excess and the decisions these animals make are critical to their survival," said Ari Friedlaender, a principal investigator with the Marine Mammal Institute at Oregon State University's Hatfield Marine Science Center and co-author on the study. "If you stick your hand into a full bag of pretzels, you're likely to grab more than if you put your hand into a bag that only had a few pretzels."

The feeding pattern that focuses more effort on the densest krill patches provides a new example of blue whale foraging specializations that support the animals' tremendous size.

This kind of lunge-feeding takes a lot more effort, but "the increase in the amount of energy they get from increased krill consumption more than makes up for it," noted Jeremy Goldbogen, a marine biologist from Stanford University and co-author on the study.

"Lunge-feeding is a unique form of 'ram-feeding' that involves acceleration to high speed and the engulfment of large volumes of prey-laden water, which they filter," Goldbogen noted. "But we now know they don't take in that water indiscriminately. They have a strategy that aims to focus feeding effort on the densest, highest-quality krill patches."

In their study, the researchers found a threshold for krill that determined how intensively the blue whales fed.

"The magic number for krill seems to be about 100 to 200 individuals in a cubic meter of water," Hazen said. "If it's below that range, blue whales use a strategy to conserve oxygen and feed less frequently. If it's above that, they'll feed at very high rates and invest more effort."

The researchers say this insight into blue whale feeding will help determine how best to protect the species, which is listed as endangered by the International Union for Conservation of Nature.

"If they are disturbed during the intense, deep-water feeding, it may not have consequences today, or this week, but it could over a period of months," Friedlaender said. "There can be impacts on their overall health, as well as on their fitness and viability for reproduction."

The study was funded by the U.S. Office of Naval Research.

Story Source: NOAA Fisheries West Coast Region. "To breathe or to eat: Blue whales forage efficiently to maintain massive body size: Blue whale feeding strategy targets highest-quality prey, maximizing energy gain." ScienceDaily. (accessed October 4, 2015).

Journal Reference:
E. L. Hazen, A. S. Friedlaender, J. A. Goldbogen. Blue whales (Balaenoptera musculus) optimize foraging efficiency by balancing oxygen use and energy gain as a function of prey density. Science Advances, 2015; 1 (9): e1500469 DOI: 10.1126/sciadv.1500469

Terrestrial predators can modulate the energy used for prey capture to maximize efficiency, but diving animals face the conflicting metabolic demands of energy intake and the minimization of oxygen depletion during a breath hold. It is thought that diving predators optimize their foraging success when oxygen use and energy gain act as competing currencies, but this hypothesis has not been rigorously tested because it has been difficult to measure the quality of prey that is targeted by free-ranging animals. We used high-resolution multisensor digital tags attached to foraging blue whales (Balaenoptera musculus) with concurrent acoustic prey measurements to quantify foraging performance across depth and prey density gradients. We parameterized two competing physiological models to estimate energy gain and expenditure based on foraging decisions. Our analyses show that at low prey densities, blue whale feeding rates and energy intake were low to minimize oxygen use, but at higher prey densities feeding frequency increased to maximize energy intake. Contrary to previous paradigms, we demonstrate that blue whales are not indiscriminate grazers but instead switch foraging strategies in response to variation in prey density and depth to maximize energetic efficiency.
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  • Claudiu Constantin Nicolaescu
Antarctica’s blue whales are split into three distinct populations

March 9, 2016 5.58am AEDT

Antarctica’s critically endangered blue whales, the world’s largest animal, are made up of three populations, according to our new DNA analysis.

Although the groups occur together when feeding in Antarctic waters, they are genetically distinct. This suggests that the three groups breed in different locations – possibly even different oceans – when they head north in the winter.

If we can find out where they go, and what hazards they face on the way, we will be a step closer to helping them recover from their near-annihilation by whalers during the 20th century.

Hidden giants

It is a daunting task to understand the ecology of the Antarctic blue whale (Balaenoptera musculus intermedia). Even though they can weigh more than 160 tonnes – the heaviest ever known animal – and reach more than 30 metres in length, locating such a rare and highly mobile species in a vast and remote ocean can be like finding a needle in a haystack. And even having tracked them down, it can be hard to deduce anything about their population structure.

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The largest animal in the worldPaula Olson, courtesy of IWC

By comparing similarities and differences in the DNA of individuals, we can tell which individuals are part of the same population and estimate the number of populations. Individuals from the same breeding population are more genetically similar than those from different populations. But we need recently collected DNA samples to do this for current populations.

The standard way to get DNA from a blue whale is to take a biopsy by firing a dart that collects a small piece of skin and blubber, bounces off the whale and floats on the water for collection. It is akin to a pinprick for an animal as massive as a whale.

Long before we started working with blue whales in 2007, expeditions have been carried out under the auspices of the International Whaling Commission to research Antarctic whales. These expeditions involved collecting precious biopsy samples from blue whales and there is now a collection stretching back to 1990.

We were granted access to samples, totalling 142 whales, and used these to create the largest and therefore most powerful genetic data set so far created for Antarctic blue whales. As our research published in Nature’s Scientific Reports shows, we found that these whales fall into three genetically distinct groups.

Where are these populations?

Blue whales, like many other whales, migrate between their Antarctic summer feeding grounds and their winter breeding grounds at lower latitudes.

We know Antarctic blue whales feed in the Antarctic, which is where they were hunted during whaling in the 20th century and where the biopsy samples were collected.

We found that individuals from the three populations occur together throughout the Antarctic, although possibly in different proportions in different areas. This is probably because the blue whales need to rove long distances around Antarctica to find the massive amounts of krill that make up their sole food source.

We suspect that the three populations go their separate ways when they head north to breed – presumably heading into the three major Southern Hemisphere ocean basins: the South Pacific, South Atlantic and Indian Oceans.

The next step will be to confirm this by finding their breeding grounds. This would involve satellite-tagging whales in Antarctic waters and then watching where they go. More biopsy samples could then be taken at the breeding grounds to confirm which populations are which.

Knowledge for conservation

Understanding the number of populations and their distribution is vital for helping Antarctica’s blue whales recover from 20th-century whaling, which reduced their numbers from 239,000 to just 360 individuals. While they are now protected from whaling, they remain critically endangered.

Some populations may be more endangered than others and may face different human threats along their migration routes and at their breeding grounds. Failing to take conservation action at a population level could therefore lead to local extinctions at these locations.

One threat that differs in intensity between locations is noise pollution, such as from seismic surveys for oil and gas as well as shipping activity. These noises can be heard underwater hundreds of kilometres from their source. Whales communicate through sound, so noise pollution can hinder their communications or, in extreme cases, make areas uninhabitable.

Our latest findings, together with our previous work on hybridisation, connectivity and population history of blue whales, provides important pieces in the puzzle of this species. But we are still at the tip of the iceberg in our understanding of the world’s largest animal and in the pathway to their recovery from whaling.

Journal Reference:
Catherine R. M. Attard, Luciano B. Beheregaray & Luciana M. Möller Towards population-level conservation in the critically endangered Antarctic blue whale: the number and distribution of their populations. Scientific Reports 6, Article number: 22291 (2016) doi:10.1038/srep22291

Population-level conservation is required to prevent biodiversity loss within a species, but it first necessitates determining the number and distribution of populations. Many whale populations are still depleted due to 20th century whaling. Whales are one of the most logistically difficult and expensive animals to study because of their mobility, pelagic lifestyle and often remote habitat. We tackle the question of population structure in the Antarctic blue whale (Balaenoptera musculus intermedia) – a critically endangered subspecies and the largest extant animal – by capitalizing on the largest genetic dataset to date for Antarctic blue whales. We found evidence of three populations that are sympatric in the Antarctic feeding grounds and likely occupy separate breeding grounds. Our study adds to knowledge of population structure in the Antarctic blue whale. Future research should invest in locating the breeding grounds and migratory routes of Antarctic blue whales through satellite telemetry to confirm their population structure and allow population-level conservation.

[Image: srep22291-f3.jpg]
Each individual is represented by a circle, which is shaded according to its highest cluster membership as estimated in STRUCTURE using microsatellites (population 1, blue or medium grey in greyscale; population 2, yellow or light grey in greyscale; population 3, red or dark grey in greyscale). Only the first recorded location is shown for individuals sampled more than once. The map position of individuals sampled from the same or similar locations has been slightly altered so that all individuals are visible, with the exception of individuals located from 0° to 20°E due to extensive sampling from this area (n = 81). A pie chart shows the proportion of individuals that belong to each STRUCTURE cluster in the area from 0° to 20°E. Borders of IWC management Areas I to VI (dashed, black latitudinal lines) and ocean basins (solid, black latitudinal lines; borders according to International Hydrographic Organization definitions110) are shown. The longitudes of the southern coasts of South America, Africa and Australia are indicated (solid, black longitudinal lines). The map was created using ARCGIS 10.0 (Esri). 
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  • Claudiu Constantin Nicolaescu
Unique feeding habits of whales revealed

Date: September 22, 2016
Source: Stanford University

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Researchers from Stanford's Hopkins Marine Station attach devices that enable them to watch a whale's behavior as though they were riding on the animal's back.
Credit: Jeremy Goldbogen
Whales are the biggest animals to ever have existed on Earth, and yet some subsist on creatures the size of a paper clip. It's a relatively common factoid, but, in truth, how they do this is only just being uncovered, thanks to new technologies.

What scientists do know is that a 160-ton blue whale's method for scooping krill is a tremendous endeavor. Swimming around 4 meters per second, it opens its triple-hinged jaws and takes in a gulp equal to about 140 percent of its mass, slowing back down to filter its snack and prepare for the next one. Blue whales feed nearly continuously when prey conditions are good during the feeding season, but for biologists, the exact mechanism remains a confounding feat of gigantic proportions.

By attaching new sensor technology to whales just before they dive, researchers from Stanford's Hopkins Marine Station have captured this energetically expensive activity in more detail than ever before, which they report now in Current Biology.

Lunging for dinner

This type of feeding, called lunge feeding, is unique to rorquals, a family of baleen whales that includes blue whales, humpbacks and minke whales. Having a precise understanding of this process gives us some clues as to how these massive animals survive on such tiny prey, which in turn will help biologists develop more effective conservation efforts.

"This feeding process is facilitated by a complex suite of biomechanical and anatomical adaptations that together allow the whales to engulf a volume of water and prey that is larger than their own body," said co-author Jeremy Goldbogen, assistant professor of biology at Stanford. "For a large blue whale, this represents a volume of water and prey that is approximately the size of a large swimming pool or a school bus, and this is engulfed in a matter of seconds."

To gulp down a mouthful of krill or fish, rorquals have to time their lunge just right. The enormous intake slows them down rapidly due to the drag caused by opening their mouths and the added burden of the water they take in.

Performing this behavior at deep depths can make it even more energetically costly.

"When these animals dive down to 300 meters, holding their breath for 12 minutes or more, they had better be sure it's worth the cost," said David Cade, lead author and PhD student in biology at Stanford. "To regain the energy lost, the prediction is that they are foraging on a pretty dense, rich resource."

New whale-top view

Sensors that record multiple facets of whale life have been around for about 15 years. Goldbogen has used them to study the reactions of blue whales to cargo ships and the lunge frequency of minke whales. These suction cup sensors can include a combination of accelerometers, magnetometers, and pressure and sound recorders.

With this equipment, researchers can tell how the whales move in three dimensions but finer details are lost. For example, in 2006 research, Goldbogen hypothesized that whales open their mouths at peak speed when lunge feeding. A competing theory later said their mouths open several seconds before the peak in speed, yet neither theory could be tested with the sensors available at the time.

To figure out which model of feeding was more accurate, Stanford researchers worked with other whale researchers and engineers to develop a sensor package that housed miniaturized versions of typical movement technology plus new video recording capabilities. They attached these tags to whales in South Africa, Patagonia, and off the west and east coasts of the United States. The resulting video is what you would see if you were riding on the whale's back.

"Combining these two modalities is really eye-opening," said Cade. "Every time we do a deployment, we get something back that's new and interesting."

The researchers found that whales that fed on krill followed a distinct pattern of activity. As Goldbogen hypothesized, they opened their mouth at peak speed and closed it around the time they were back to normal speed. Humpbacks that fed on fish, however, varied their timing. This is likely in response to the more advanced escape abilities of fish compared to krill; the whales may be performing lunge feeding that is less energetically ideal when the trade-off is eating prey that can supply them with more energy.

Save the whales … and the fish

Effective Oct. 11, most populations of humpback whales will be removed from the endangered species list. Even accounting for that change, three of the eight species of rorquals are endangered. There is insufficient data to determine the status for three other species in this family. Any attempt to ensure the survival of these giants will require us to know much more about them, including the particulars of their mealtime activities.

"Because they operate on an energetic knife-edge, any changes in the environment related to their food supply could have profound impacts on individual and population health," said Goldbogen.

This research could also help us better determine the impact whales have on our ocean resources. Whales have previously been blamed for reduction in fish populations but, although there are estimates, we don't actually know how much a whale eats, said Cade.

These predators have played important roles in our ecosystem for millions of years, and the mass removal of them has had a poorly understood effect on ocean ecology as a whole. Learning more about rorqual feeding habits can support conservation efforts while also furthering insights into ecosystem processes that have direct effects on human fisheries. As for their part, the Hopkins researchers hope to dive deeper into whale feeding studies, including figuring out the fluid mechanics of their iconic baleen, which acts as a high-throughput filter to process the vast amounts of small prey.

Additional authors on this paper include Ari S. Friedlaender of Oregon State University and John Calambokidis of Cascadia Research Collective. The study, titled "Kinematic Diversity in Rorqual Whale Feeding Mechanisms," is published in Current Biology.

Story Source: Stanford University. "Unique feeding habits of whales revealed." ScienceDaily. (accessed September 23, 2016).

Journal Reference:
David E. Cade, Ari S. Friedlaender, John Calambokidis, Jeremy A. Goldbogen. Kinematic Diversity in Rorqual Whale Feeding Mechanisms. Current Biology, September 2016 DOI: 10.1016/j.cub.2016.07.037

•Tags with both video and 3D accelerometry were deployed on feeding rorquals
•Skull movement could be observed in concert with animal orientation and motion
•Lunging whales displayed prey-dependent inter- and intra-species kinematic diversity
•Humpback whales most likely sacrifice energy efficiency to increase foraging flexibility

Rorqual whales exhibit an extreme lunge filter-feeding strategy characterized by acceleration to high speed and engulfment of a large volume of prey-laden water. Although tagging studies have quantified the kinematics of lunge feeding, the timing of engulfment relative to body acceleration has been modeled conflictingly because it could never be directly measured. The temporal coordination of these processes has a major impact on the hydrodynamics and energetics of this high-cost feeding strategy. If engulfment and body acceleration are temporally distinct, the overall cost of this dynamic feeding event would be minimized. However, greater temporal overlap of these two phases would theoretically result in higher drag and greater energetic costs. To address this discrepancy, we used animal-borne synchronized video and 3D movement sensors to quantify the kinematics of both the skull and body during feeding events. Krill-feeding blue and humpback whales exhibited temporally distinct acceleration and engulfment phases, with humpback whales reaching maximum gape earlier than blue whales. In these whales, engulfment coincided largely with body deceleration; however, humpback whales pursuing more agile fish demonstrated highly variable coordination of skull and body kinematics in the context of complex prey-herding techniques. These data suggest that rorquals modulate the coordination of acceleration and engulfment to optimize foraging efficiency by minimizing locomotor costs and maximizing prey capture. Moreover, this newfound kinematic diversity observed among rorquals indicates that the energetic efficiency of foraging is driven both by the whale’s engulfment capacity and the comparative locomotor capabilities of predator and prey.
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  • Claudiu Constantin Nicolaescu
Data on blue whales off California helps protect their distant relatives
Research identifies blue whale habitat in the Northern Indian Ocean

Date: February 8, 2017
Source: NOAA Fisheries West Coast Region
A research team has found a way to translate their knowledge of blue whales off California and in the eastern tropical Pacific Ocean to the other side of the world, revealing those areas of the Northern Indian Ocean where whales are likely to be encountered.

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This is a blue whale photographed during a survey of marine mammals in the eastern Pacific Ocean conducted by the Marine Mammal and Turtle Division at NOAA Fisheries' Southwest Fisheries Science Center.
Credit: NOAA Fisheries/Southwest Fisheries Science Center/James W. Gilpatrick, Jr. and Morgan S. Lynn

Scientists know a great deal about blue whales off California, where the endangered species has been studied for decades.

But they know far less about blue whales in the Northern Indian Ocean, where ships strike and kill some of the largest animals on Earth.

Now a research team has found a way to translate their knowledge of blue whales off California and in the eastern tropical Pacific Ocean to the other side of the world, revealing those areas of the Northern Indian Ocean where whales are likely to be encountered. The team of scientists from NOAA Fisheries and the Sri Lankan Blue Whale Project published the findings in the journal Diversity and Distributions.

The Scientific Committee of the International Whaling Commission included the results of the study when assessing a shift in busy shipping lanes off the south coast of Sri Lanka that will reduce the danger to whales in an important feeding area.

"Small changes in shipping routes can be a very effective way to address a serious conservation issue with minimal inconvenience to the shipping industry, but rely on a good understanding of the relationship between whale distribution and habitat," said Russell Leaper, a member of the Scientific Committee. "This study makes an important contribution towards that understanding."

To meet requirements of the U.S. Marine Mammal Protection Act, NOAA Fisheries regularly conducts marine mammal and ecosystem assessment surveys. Surveys off the U.S. West Coast and in the eastern tropical Pacific have shown that the upwelling of deep ocean water rich in nutrients supports dense patches of krill that blue whales feed on. This information has proven critical in addressing the emerging problem of ships striking blue whales, and has informed the management of ship traffic to and from the busy ports of Los Angeles and Long Beach to mitigate this problem.

"We are fortunate in the United States to have some of the best marine mammal data sets in the world," said Jessica Redfern, a research scientist at NOAA Fisheries Southwest Fisheries Science Center in La Jolla, Calif., and lead author of the new study. "It was exciting to explore how we could use these data sets to aid conservation efforts in parts of the world where few data exist."

The research developed computer models of blue whale habitat off the U.S. West Coast and in the eastern tropical Pacific, including upwelling and underwater topography that affects areas of krill concentration. The models then identified similar upwelling and feeding regions in the Northern Indian Ocean that are also likely to be important habitat for the endangered species.

"The Sri Lankan Blue Whale Project has spear-headed efforts to draw attention to and mitigate the risk of ships striking blue whales in Sri Lankan waters. To best protect this species in this data-limited region, it is essential to adapt approaches developed in other parts of the world. Our collaboration achieves just that," said Asha de Vos, founder of the Sri Lankan Blue Whale Project and a coauthor on the study.

The Northern Indian Ocean and its inhabitants have not been surveyed to the same extent as the eastern Pacific Ocean, and much of the information about whale distributions comes from Soviet whaling several decades ago. However, the model results matched up well with the limited information available, the scientists reported.

The model suggests that the distribution of blue whales in the Northern Indian Ocean may shift seasonally, following their food as monsoon climate patterns alter the most productive habitat. The scientists concluded that research and monitoring is critical in the areas identified as blue whale habitat in the Northern Indian Ocean because many of these areas overlap with some of the busiest shipping routes in the world.

"Marine mammals face threats from human activities in most of the world's oceans, but we lack the data needed to address these threats in many areas," Redfern said. "The data collected aboard our surveys allow us to predict species habitat in other parts of the world. Understanding species habitat allows us to address conservation problems that are often unexpected and critical to maintaining healthy populations."

Story Source: NOAA Fisheries West Coast Region. "Data on blue whales off California helps protect their distant relatives: Research identifies blue whale habitat in the Northern Indian Ocean." ScienceDaily. (accessed February 9, 2017).

Journal Reference:
Jessica V. Redfern, Thomas J. Moore, Paul C. Fiedler, Asha de Vos, Robert L. Brownell, Karin A. Forney, Elizabeth A. Becker, Lisa T. Ballance. Predicting cetacean distributions in data-poor marine ecosystems. Diversity and Distributions, 2017; DOI: 10.1111/ddi.12537


Human activities are creating conservation challenges for cetaceans. Spatially explicit risk assessments can be used to address these challenges, but require species distribution data, which are limited for many cetacean species. This study explores methods to overcome this limitation. Blue whales (Balaenoptera musculus) are used as a case study because they are an example of a species that have well-defined habitat and are subject to anthropogenic threats.
Eastern Pacific Ocean, including the California Current (CC) and eastern tropical Pacific (ETP), and northern Indian Ocean (NIO).
We used 12 years of survey data (377 blue whale sightings and c. 225,400 km of effort) collected in the CC and ETP to assess the transferability of blue whale habitat models. We used the models built with CC and ETP data to create predictions of blue whale distributions in the data-poor NIO because key aspects of blue whale ecology are expected to be similar in these ecosystems.
We found that the ecosystem-specific blue whale models performed well in their respective ecosystems, but were not transferable. For example, models built with CC data could accurately predict distributions in the CC, but could not accurately predict distributions in the ETP. However, the accuracy of models built with combined CC and ETP data was similar to the accuracy of the ecosystem-specific models in both ecosystems. Our predictions of blue whale habitat in the NIO from the models built with combined CC and ETP data compare favourably to hypotheses about NIO blue whale distributions, provide new insights into blue whale habitat, and can be used to prioritize research and monitoring efforts.
Main conclusions
Predicting cetacean distributions in data-poor ecosystems using habitat models built with data from multiple ecosystems is potentially a powerful marine conservation tool and should be examined for other species and regions.;jsessionid=5071B237418EFC85F4E0BCC164CBFFDA.f03t04 
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  • Claudiu Constantin Nicolaescu
Righty blue whales sometimes act like lefties, study finds

Date: November 20, 2017
Source: Cell Press
To support their hulking bodies, blue whales use various acrobatic maneuvers to scoop up many individually tiny prey, filtering the water back out through massive baleen plates. In most cases, the whales roll to the right as they capture their prey, just as most people are right-handed. But, researchers now show that the whales shift directions and roll left when performing 360° barrel rolls in shallow water.

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A blue whale dives into the water off the California coast.
Credit: Craig Hayslip, Oregon State University Marine Mammal Institute

Blue whales are the largest animals in the world, with bodies that can weigh as much as 25 elephants and extend over the length of a basketball court. To support their hulking bodies, the whale use various acrobatic maneuvers to scoop up many individually tiny prey, filtering the water back out through massive baleen plates. In most cases, the whales roll to the right as they capture their prey, just as most people are right-handed. But, researchers reporting in Current Biology on November 20 now show that the whales shift directions and roll left when performing 360° barrel rolls in shallow water.

The findings offer the first evidence of "handedness" in blue whales, the researchers say. They also highlight the importance of studying animals in their natural three-dimensional environments for revealing phenomena that may be impossible to capture in a captive environment.

"We believe that this left-side bias is the result of the whales maintaining a visual connection with their prey with their right eye," says Ari Friedlaender at the University of California, Santa Cruz. "If the whales turned to the right on approach, they would lose sight of their prey and decrease the ability to forage successfully. By rolling to the left, the whales may be maintaining this visual connection to their prey."

"To the best of our knowledge, this is the first example where animals show different lateralized behaviors depending on the context of the task that is being performed," says study co-author James Herbert-Read from Stockholm University in Sweden.

Friedlaender and his colleagues have long studied blue whales' feeding behaviors in an attempt to understand how they can support their large bodies. In the new study, the researchers attached motion-sensing tags to 63 blue whales living off the coast of California to capture how the animals move as they engulf their prey.

In total, the researchers collected data on more than 2,800 rolling lunges for prey to find that the animals approach their prey using two different rolling behaviors. In some cases, they roll to the side and then back, turning 180° or less. In other cases, they go in for a complete barrel roll that takes them around full circle.

The evidence shows that individual whales have a preference as to whether they roll to the right or the left. The vast majority of the whales showed a preference for rolling to the right, much as more people show a preference for using their right hands. But, the whales also showed some flexibility in their approach. When the animals did a barrel roll in shallow water to attack a small patch of prey from below at a steep angle, they more often spun left, going against their general preference.

The findings are the first to demonstrate a left-side bias for a lateralized routine behavior, the researchers say. They also highlight blue whales' adaptability when it comes to feeding behaviors. The whales shift their foraging strategies depending on where they are feeding in the water column, how their prey are behaving, and how they need to maneuver to forage successfully.

"We were completely surprised by these findings, but when considering the means by which the whales attack smaller prey patches, the behavior really seems to be effective, efficient, and in line with the mechanisms that drive their routine foraging behaviors," Friedlaender says.

"While most other large baleen whales that lunge-feed can feed on both krill patches and small forage fish like anchovies and herring, blue whales feed almost exclusively on krill patches and seem to exhibit feeding strategies to maximize their intake of as many krill as possible with each energetically costly feeding event," adds co-author Dave Cade at Stanford University.

The researchers say the next step is to conduct similar studies on related species of whales to understand whether the behaviors seen in blue whales also exist in them. They're also developing new technologies to capture even finer details of the whales' underwater movements.

Story Source: Cell Press. "Righty blue whales sometimes act like lefties, study finds." ScienceDaily. (accessed November 20, 2017).

Journal Reference:
Friedlaender et al. Context dependent lateralized feeding strategies 1 in blue whales. Current Biology, 2017 DOI: 10.1016/j.cub.2017.10.023

Lateralized behaviors benefit individuals by increasing task efficiency in foraging and anti-predator behaviors [1–4] . The conventional lateralization paradigm suggests individuals are left or right lateralized, although the direction of this laterality can vary for different tasks (e.g. foraging or predator inspection/avoidance). By fitting tri-axial movement sensors to blue whales (Balaenoptera musculus), and by recording the direction and size of their rolls during lunge feeding events, we show how these animals differ from such a paradigm. The strength and direction of individuals’ lateralization were related to where and how the whales were feeding in the water column. Smaller rolls (≤180°) predominantly occurred at depth (>70 m), with whales being more likely to rotate clockwise around their longest axis (right lateralized). Larger rolls (>180°), conversely, occurred more often at shallower depths (<70 m) and were more likely to be performed anti-clockwise (left lateralized). More acrobatic rolls are typically used to target small, less dense krill patches near the water’s surface [5,6] , and we posit that the specialization of lateralized feeding strategies may enhance foraging efficiency in environments with heterogeneous prey distributions.
Attached to this post:[Image: attach.png] Context_dependent_lateralized_feeding_strategies_in_blue_whales.pdf (383.85 KB)
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  • Claudiu Constantin Nicolaescu
Diving deep into the blue whale genome reveals the animals’ extraordinary evolutionary history

Date: April 5, 2018
Source: Senckenberg Research Institute and Natural History Museum

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Blue Whale underwater.
Credit: © aroderick / Fotolia

For the first time, scientists of the German Senckenberg Biodiversity and Climate Research Center, Goethe University and the University of Lund in Sweden have deciphered the complete genome of the blue whale and three other rorquals. These insights now allow tracking the evolutionary history of the worlds’ largest animal and its relatives in unprecedented detail. Surprisingly, the genomes show that rorquals have been hybridizing during their evolutionary history. In addition, rorquals seem to have separated into different species in the absence of geographical barriers. This phenomenon, called sympatric speciation, is very rare in animals. The study has just been published in Science Advances.

Blue whales are the giants of the sea. With up to 30 meters (100 feet) long and weighing up to 175 tons, they are the largest animals that ever evolved on earth; larger even than dinosaurs. Short of becoming extinct due to whaling by the end of the 80s, currently the populations of the gentle giants are slowly recovering. Now new research highlights that the evolution of these extraordinary animals and other rorquals was also anything but ordinary.

A research team led by Professor Axel Janke, evolutionary geneticist at the Senckenberg Biodiversity and Climate Research Center and Goethe University, has found that the rorquals, including the blue whale, mated across emerging species boundaries. “Speciation under gene flow is rare. Usually, species are assumed to be reproductively isolated because geographical or genetic barriers inhibits genetic exchange. Apparently however, this does not apply to whales”, explains Fritjof Lammers, co-lead-author of the study, Senckenberg Biodiversity and Climate Research Centre.

Teaming up with cetacean specialist Professor Ulfur Arnason at University of Lund, Sweden, Lammers and his colleagues are the first to have sequenced the complete genome of the blue whale and other rorquals, including the humpback and the gray whale. For these migratory whales, geographical barriers do not exist in the vastness of the ocean, instead some rorquals differentiated by inhabiting different ecological niches. Cross-genome analyses now indicate that there are apparently no genetic barriers between species and that there has been gene flow among different rorqual species in the past.

This is confirmed by spotting hybrids between fin and blue whales still to date, which have been witnessed and genetically studied by Professor Arnason. However, the researchers could not detect traces of recent liaisons between the two species in their genomes. This is probably because whale genomes are currently known only from one or two individuals.

To track down the rorquals’ evolution, the scientists have applied so-called evolutionary network analyses. "In these analyses, speciation is not considered as a bifurcating phylogenetic tree as Darwin has envisioned it, but as an interwoven network. This allows us to discover hidden genetic signals, that otherwise would have stayed undetected", says Janke.

Overall, the research also shows that the relationships among the rorqual species are more complicated than hitherto thought. So far, the humpback whale has been seen as an outsider among the rorquals because of its enormous fins. The genome reveals that this classification does match the evolutionary signals. The same is true for the gray whale, which was believed to be evolutionarily distinct from rorquals due to its appearance. Genomic analyses show however that gray whales are nested within rorquals. Gray whales just happened to occupy a new ecological niche by feeding on crustaceans in coastal oceanic waters.

"Our research highlights the enormous potential of genome sequencing to better understand biological processes and the fundamentals of biodiversity. It even reveals how population sizes of whales have changed during the last million years", summarizes Janke. Janke is one of the leading researchers at the Hessian LOEWE Research Centre for Translational Biodiversity Genomics (LOEWE-TBG). Launched in January 2018, LOEWE-TBG is set to systematically analyze complete genomes or all active genes. The research center is envisaged to do basic research with a strong emphasis on transferring knowledge to benefit the study of natural products and protect biodiversity.

Story Source: Senckenberg Research Institute and Natural History Museum. "Diving deep into the blue whale genome reveals the animals’ extraordinary evolutionary history." ScienceDaily. (accessed April 5, 2018).

Journal Reference:
Arnason, U. et. al. Whole genome sequencing of the blue whale and other rorquals find signatures for introgressive gene flow. Science Advances, 2018) DOI: 10.1126/sciadv.aap9873

Reconstructing the evolution of baleen whales (Mysticeti) has been problematic because morphological and genetic analyses have produced different scenarios. This might be caused by genomic admixture that may have taken place among some rorquals. We present the genomes of six whales, including the blue whale (Balaenoptera musculus), to reconstruct a species tree of baleen whales and to identify phylogenetic conflicts. Evolutionary multilocus analyses of 34,192 genome fragments reveal a fast radiation of rorquals at 10.5 to 7.5 million years ago coinciding with oceanic circulation shifts. The evolutionarily enigmatic gray whale (Eschrichtius robustus) is placed among rorquals, and the blue whale genome shows a high degree of heterozygosity. The nearly equal frequency of conflicting gene trees suggests that speciation of rorqual evolution occurred under gene flow, which is best depicted by evolutionary networks. Especially in marine environments, sympatric speciation might be common; our results raise questions about how genetic divergence can be established.
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  • Claudiu Constantin Nicolaescu
Migrating blue whales rely on memory more than environmental cues to find prey

February 25, 2019, Oregon State University

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Blue whale photograph taken during Oregon State University Marine Mammal Program's August, 2005 field season tagging Blue and Humpback whales off the central California coast for the Tagging of Pacific Pelagic (TOPP) research project. Credit: Oregon State University

Blue whales reach their massive size by relying on their exceptional memories to find historically productive feeding sites rather than responding in real time to emerging prey patches, a new study concludes.

Researchers examining records of both whale migration and oceanic conditions in the California Current Ecosystem found that blue whales almost perfectly match the timing of their migration to the historical average timing of krill production, rather than matching the waves of krill availability in any given year.

The findings suggest that blue whales locate prey by relying on memory to return to stable, high-quality foraging sites, which historically have served them well but could make it difficult for the whales to adapt if novel ecosystem changes emerge as a result of climate change.

Results of the study are being published next week in Proceedings of the National Academy of Sciences.

The concept of tracking the timing of food availability along migration routes is not unusual for land animals, but it has been more difficult to identify in marine creatures, according to Briana Abrahms, a research ecologist with the NOAA Southwest Fisheries Science Center in Monterey, Calif., and lead author on the study.

"We know that many species that migrate on land, from caribou in the Arctic to wildebeests in the Serengeti, enhance their survival by carefully adjusting the pace and timing of their migrations to find food as it becomes seasonally available along the way, rather than just migrating to get from point A to point B," Abrahms said.

Blue whales seem to embrace that same strategy, which is enhanced by their memory, she noted. "These long-lived, highly intelligent animals are making movement decisions based on their expectations of where and when food will be available during their migrations."

"This novel study is particularly noteworthy in that if focuses on the phenology, or timing of migration in a large marine predator," said Sue Moore, an affiliate professor at the University of Washington Center for Ecosystem Sentinels, who was not involved in the study.

[Image: 1-migratingblu.jpg]
Photograph of blue whale taken during Oregon State University Marine Mammal Institutes 2016 tagging field season off southern California. Credit: Oregon State University

The study also raises the question of what will happen to the population if changing climate conditions cause food availability to deviate strongly from the whales' expectations.

The interdisciplinary research team used 10 years of tagging data from the Marine Mammal Institute at Oregon State University to determine daily blue whale movements of 60 individual whales in the California Current Ecosystem, and then compared that with satellite-based measurements of ocean productivity.

"We think that blue whales have evolved to use historical migration routes and timing that put them in proximity to the most predictably high production feeding areas and then make minor adjustments based on local conditions," said Daniel Palacios, a principal investigator with Oregon State's Marine Mammal Institute and a co-author on the study.

"There are various time scales of events that could change the timing of phytoplankton blooms—and thus the availability of the whales' preferred prey, krill," he noted, "including La Nina and El Nino events and the Pacific Decadal Oscillation. But the whales' strategy of relying on memory and historic timing at least gets them into 'the Goldilocks zone.'"

Blue whales can grow to the length of a basketball court, weigh as much as 25 large elephants, and their mouths can hold 100 people, though their diet is primarily krill—tiny shrimp-like creatures less than two inches in length. The blue whale is thought to be the largest creature to ever inhabit the Earth, yet little was known about their range or where they went to breed until Oregon State's Bruce Mate led a series of tracking studies featured in the popular 2009 National Geographic documentary, "Kingdom of the Blue Whale."

"There is still a lot we don't know about blue whales, but it is apparent that they have strong fidelity to certain sites along the West Coast of the United States, which they use year after year," said Mate, who directs OSU's Marine Mammal Institute.

An estimated 2,500 of the world's 10,000 blue whales spend time in the waters off the West Coast of the Americas and are known as the eastern North Pacific population. The huge whales can travel from the Gulf of Alaska all the way down to an area near the equator known as the Costa Rica Dome. The majority of the population spends the summer and fall in the waters off the U.S. West Coast, with the tagged whales most heavily using areas off Santa Barbara and San Francisco, California, which puts them in routine peril from ship strikes.

"We still have a lot to learn about how large animals navigate in the ocean, how they find good habitat and how they are affected by human activities and environmental changes," said NOAA's Abrahms.

Understanding how blue whales make movement decisions give scientists insight into how they may, or may not, be able to cope with changing ocean conditions in the future, she added.

Journal Reference:
Briana Abrahms el al., "Memory and resource tracking drive blue whale migrations," PNAS(2019).

In terrestrial systems, the green wave hypothesis posits that migrating animals can enhance foraging opportunities by tracking phenological variation in high-quality forage across space (i.e., “resource waves”). To track resource waves, animals may rely on proximate cues and/or memory of long-term average phenologies. Although there is growing evidence of resource tracking in terrestrial migrants, such drivers remain unevaluated in migratory marine megafauna. Here we present a test of the green wave hypothesis in a marine system. We compare 10 years of blue whale movement data with the timing of the spring phytoplankton bloom resulting in increased prey availability in the California Current Ecosystem, allowing us to investigate resource tracking both contemporaneously (response to proximate cues) and based on climatological conditions (memory) during migrations. Blue whales closely tracked the long-term average phenology of the spring bloom, but did not track contemporaneous green-up. In addition, blue whale foraging locations were characterized by low long-term habitat variability and high long-term productivity compared with contemporaneous measurements. Results indicate that memory of long-term average conditions may have a previously underappreciated role in driving migratory movements of long-lived species in marine systems, and suggest that these animals may struggle to respond to rapid deviations from historical mean environmental conditions. Results further highlight that an ecological theory of migration is conserved across marine and terrestrial systems. Understanding the drivers of animal migration is critical for assessing how environmental changes will affect highly mobile fauna at a global scale.
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  • Claudiu Constantin Nicolaescu
Sonar disturbs blue whales feeding

March 4, 2019, The Company of Biologists

[Image: bluewhale.jpg]
Credit: CC0 Public Domain

No one really knows why pods of whales spontaneously drive themselves aground. Military sonar may be one culprit, and the need to train and test submarine tracking technology in open water could put the US Navy in conflict with the gentle cetaceans that feed and pass through military ranges. Although solitary endangered blue whales are rarely victims of sonar stranding, this does not mean that they are unaffected by high intensity sonar. 'We wanted to understand better what the common behavioural responses are in blue whales when they are exposed to [sonar]', says Brandon Southall from the University of California, Santa Cruz, USA. So, he and a team of 14 colleagues embarked on a marathon tracking program to investigate the reactions of blue whales to sonar. The team publish their discovery that blue whales stop feeding on deep patches of krill when they encounter sonar in Journal of Experimental Biology.

'The ocean is a big place and it can be easy to miss and lose even the biggest animals ever on the planet, but, because they are so large and have very tall blows, they are actually among the easiest marine mammals to track', says Southall. Admitting that being close to one of these incredible animals can be daunting, Southall explains how the scientists manoeuvred close (~5 m) to the colossal animals in a 6 m inflatable boat to attach the suction tags, which record the animals' depth, movements and sounds in the water. 'The driver of the small boat is totally critical', says Southall, adding, 'we had one of the most experienced people in the world doing this: John Calambokidis from the Cascadia Research Collective'.

Once the tag was attached and six trained observers were in place to confirm the animal's movements at the surface, the team generated sonar signals from a boat located about 1 km away for 30 min or an hour. During this time, they monitored the animals' reactions, first as the sonar became louder and then after the noise ceased. In addition, Ari Friedlander and Elliot Hazen used echosounders to track krill—the whales' favourite delicacy—when conditions in the vicinity permitted, to get a better idea of when and where the whales were in relation to their dinner.

After successfully recording the responses of whales to 42 sonar tests over 5 years, Stacy DeRuiter, led a team analysing the information logged by the tags, which Southall then combined with observations at the surface, to look for patterns and potential changes in the whales' behaviour.

Intriguingly, the majority of the deep-diving whales stopped feeding when the sonar signals started up; however, the whales near the surface generally didn't respond at all, even when the sonar was loud and nearby. In addition, some of the animals that had stopped feeding turned and headed away from the sonar emitter, although most resumed their activities soon after the sonar stopped. Southall admits that he was surprised by how different the whales' reactions were. 'Some whales responded when the sound was barely audible, while others seemingly ignored it and kept feeding at quite loud levels', says Southall, which is a 'really big deal', he adds. 'The current management approaches rely very heavily on the amplitude level [volume] to predict response', he explains. However, the activity that the whale is engaged in seems to have a larger impact on the degree to which the sonar disrupts its behaviour.

Considering the effects of sonar, Southall suggests, 'Impacts could be minimized by reducing sonar disturbance during periods of blue whale foraging on deep patches of krill in the military's main training areas'. He and his colleagues are also keen to learn how the animals determine the proximity of a sonar source, to decide when it's time to stop feeding and flee.

Journal Reference:
Southall, B. L., DeRuiter, S. L., Friedlaender, A., Stimpert, A. K., Goldbogen, J. A., Hazen, E., Casey, C., Fregosi, S., Cade, D. E., Allen, A. N. et al. (2019). Behavioral responses of individual blue whales (Balaenoptera musculus) to mid-frequency military sonar. J. Exp. Biol. 222, jeb190637. DOI: 10.1242/jeb.190637

This study measured the degree of behavioral responses in blue whales (Balaenoptera musculus) to controlled noise exposure off the southern California coast. High-resolution movement and passive acoustic data were obtained from non-invasive archival tags (n=42) whereas surface positions were obtained with visual focal follows. Controlled exposure experiments (CEEs) were used to obtain direct behavioral measurements before, during and after simulated and operational military mid-frequency active sonar (MFAS), pseudorandom noise (PRN) and controls (no noise exposure). For a subset of deep-feeding animals (n=21), active acoustic measurements of prey were obtained and used as contextual covariates in response analyses. To investigate potential behavioral changes within individuals as a function of controlled noise exposure conditions, two parallel analyses of time-series data for selected behavioral parameters (e.g. diving, horizontal movement and feeding) were conducted. This included expert scoring of responses according to a specified behavioral severity rating paradigm and quantitative change-point analyses using Mahalanobis distance statistics. Both methods identified clear changes in some conditions. More than 50% of blue whales in deep-feeding states responded during CEEs, whereas no changes in behavior were identified in shallow-feeding blue whales. Overall, responses were generally brief, of low to moderate severity, and highly dependent on exposure context such as behavioral state, source-to-whale horizontal range and prey availability. Response probability did not follow a simple exposure–response model based on received exposure level. These results, in combination with additional analytical methods to investigate different aspects of potential responses within and among individuals, provide a comprehensive evaluation of how free-ranging blue whales responded to mid-frequency military sonar.
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  • Claudiu Constantin Nicolaescu
Modeling predicts blue whales' foraging behavior, aiding population management efforts

Date: July 17, 2019
Source: Oregon State University

[Image: 190717230334_1_900x600.jpg]
Blue whale tail (stock image). Credit: © Charlotte / Adobe Stock

Scientists can predict where and when blue whales are most likely to be foraging for food in the California Current Ecosystem, providing new insight that could aid in the management of the endangered population in light of climate change and blue whale mortality due to ship strikes, a new study shows.

The statistical model used for the predictions combines long-term satellite tracking data of the whales' movement patterns with environmental data such as ocean temperatures and depth, which helps researchers understand how climate variations might impact blue whales over time from a larger "ecosystem" view of the population.

"Most management decisions up to now have been based on locations where the whales tend to be found," said Daniel Palacios, who holds the Endowed Faculty in Whale Habitats position at Oregon State University's Marine Mammal Institute, and is lead author of the study.

"But it's not just where the whales are, but also the activity -- are they actually eating there or simply moving through -- that matters. This model can tell us which areas are the most important for actual foraging."

The findings were published today in the journal Movement Ecology.

Blue whales can grow 70 to 90 feet long and weigh 200,000 to 300,000 pounds, though their diet is primarily krill -- tiny shrimp-like creatures less than two inches in length. They are listed as endangered under the U.S. Endangered Species Act and the International Union for Conservation of Nature's Red List.

An estimated 1,600 of the world's 10,000 blue whales, known as the North Pacific population, spend time in the waters off the West Coast of the Americas. The North Pacific blue whale population can travel from the Gulf of Alaska to an area near the equator known as the Costa Rica Dome. The majority spend the summer and fall in the waters off the U.S. West Coast.

The California Current Ecosystem is the span of waters off the West Coast of North America extending roughly from the border with Canada at the north to Baja California, Mexico, at the south. Steady winds during spring and summer fuel a rich and biologically productive ecosystem. The study focused only on U.S. waters within this ecosystem.

The researchers' goal for the study was to better understand the blue whale behavior in the context of this ecosystem by examining the relationship between feeding behavior and ocean conditions during the feeding season.

Palacios and colleagues used long-term satellite tracking data from 72 tagged blue whales as well as ocean condition data from remote sensing during the same period, 1998 to 2008. Little was known about the blue whale until the 1990s, when Bruce Mate, director of OSU's Marine Mammal Institute, pioneered the satellite tracking studies that produced a wealth of data not previously available.

The data used in the foraging study included several years of cool, productive ocean conditions as well as a couple of warm, low-productivity years, during which food was less likely to be plentiful.

The researchers found that blue whales were more likely to exhibit foraging behavior in areas known from earlier studies for hosting large whale aggregations, providing an improved understanding of the relationship between environmental conditions and whale habitat use.

"The same environmental parameters -- water temperature, depth, abundance of phytoplankton -- that drive hotspots of whale aggregation also drive where foraging behavior is more likely to occur," Palacios said. "While this was not necessarily surprising, it was good to be able to demonstrate that we can predict whale behavioral states, as this helps inform management in terms of not just what areas are used more often by the whales, but also what they do once they get there."

They also found that whales were less likely to exhibit foraging behavior when they were further away from the coastline. The primary foraging hotspots are found in a few locations along the coast, where krill aggregations are typically most dense and persistent.

The study also supported findings from another recent paper by Palacios and colleagues that showed that blue whales rely on long-term memory to find the best places to forage, and return to them year after year. That makes them susceptible to climatic disruptions to their prey base, as the whales may take some time before they abandon their traditional foraging sites.

Improved understanding of the species-environment relationship, through an ecosystem view of whale behavior, can give researchers a better understanding of how climate change might impact whale feeding, Palacios said.

The study also could help with population management decisions. North Pacific blue whales tend to aggregate in three primary areas: Point Conception and the Santa Barbara Channel in southern California; around the Gulf of Farallones in central California; and between Cape Mendocino and Cape Blanco in northern California and southern Oregon.

Two of those hotspots are in areas of intense commercial shipping traffic near Los Angeles and San Francisco. Blue whale mortality due to ship strikes is a growing concern.

"If there are some areas along the coast that are more biologically important for the whales, based on intensified foraging activity, that's important for management agencies to know, compared to areas where the whales are just passing through," Palacios said.

The researchers' next step is to look more closely at how whales' behavior shifts during years when ocean conditions are unfavorable for food production.

"How long will it take blue whales to abandon their historic feeding grounds if the food is no longer there?" Palacios said. "If they do respond to environmental changes, how do we predict that change long-term?"

Other researchers on the study include Bruce Mate and Ladd Irvine of OSU's Marine Mammal Institute; Helen Bailey of the University of Maryland; and Elizabeth Becker, Steven Bograd, Monica DeAngelis, Karin Forney and Elliott Hazen of the National Oceanic and Atmospheric Administration.

Journal Reference:
Daniel M. Palacios, Helen Bailey, Elizabeth A. Becker, Steven J. Bograd, Monica L. DeAngelis, Karin A. Forney, Elliott L. Hazen, Ladd M. Irvine, Bruce R. Mate. Ecological correlates of blue whale movement behavior and its predictability in the California Current Ecosystem during the summer-fall feeding season. Movement Ecology, 2019; 7 (1) DOI: 10.1186/s40462-019-0164-6


Species distribution models have shown that blue whales (Balaenoptera musculus) occur seasonally in high densities in the most biologically productive regions of the California Current Ecosystem (CCE). Satellite telemetry studies have additionally shown that blue whales in the CCE regularly switch between behavioral states consistent with area-restricted searching (ARS) and transiting, indicative of foraging in and moving among prey patches, respectively. However, the relationship between the environmental correlates that serve as a proxy of prey relative to blue whale movement behavior has not been quantitatively assessed.
We investigated the association between blue whale behavioral state and environmental predictors in the coastal environments of the CCE using a long-term satellite tracking data set (72 tagged whales; summer-fall months 1998–2008), and predicted the likelihood of ARS behavior at tracked locations using nonparametric multiplicative regression models. The models were built using data from years of cool, productive conditions and validated against years of warm, low-productivity conditions.
The best model contained four predictors: chlorophyll-a, sea surface temperature, and seafloor aspect and depth. This model estimated highest ARS likelihood (> 0.8) in areas with high chlorophyll-a levels (> 0.65 mg/m3), intermediate sea surface temperatures (11.6-17.5 °C), and shallow depths (< 850 m). Overall, the model correctly predicted behavioral state throughout the coastal environments of the CCE, while the validation indicated an ecosystem-wide reduction in ARS likelihood during warm years, especially in the southern portion. For comparison, a spatial coordinates model (longitude × latitude) performed slightly better than the environmental model during warm years, providing further evidence that blue whales exhibit strong foraging site fidelity, even when conditions are not conducive to successful foraging.
We showed that blue whale behavioral state in the CCE was predictable from environmental correlates and that ARS behavior was most prevalent in regions of known high whale density, likely reflecting where large prey aggregations consistently develop in summer-fall. Our models of whale movement behavior enhanced our understanding of species distribution by further indicating where foraging was more likely, which could be of value in the identification of key regions of importance for endangered species in management considerations. The models also provided evidence that decadal-scale environmental fluctuations can drive shifts in the distribution and foraging success of this blue whale population.

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  • Claudiu Constantin Nicolaescu, theGrackle

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