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Northern Quoll - Dasyurus hallucatus
Northern Quoll - Dasyurus hallucatus

[Image: photo.jpg]

Kingdom: Animalia 
Phylum: Chordata 
Class: Mammalia 
Order: Dasyuromorphia 
Family: Dasyuridae 
Genus: Dasyurus 

The Northern Quoll (Dasyurus hallucatus), also known as the Northern Native Cat, the Satanellus, the North Australian Native Cat or the Njanmak (in the indigenous Mayali language), is a carnivorous marsupial mammal, native to Australia. There are six quoll species in the family Dasyuridae, but only four in Australia.

Physical Description
Average head-body length:
12-31 cm (male); 13-30 cm (female)

Tail length:
13-31 cm (male); 20-30 cm (female)

Average weight:
0.4-0.9 kg (male); 0.3-0.5 kg (female)

The smallest of the quolls (about the size of a large kitten), the northern quoll has grey-brown to brown fur with large white spots, and an unspotted tail. It is the most tree-based of the four quolls, and its diet includes small mammals, reptiles, worms, ants, termites, moths, honey and soft fruit.

[Image: photo.jpg]

The northern quoll once occurred across northern Australia from the Pilbara of Western Australia to south-eastern Queensland. Its range has become fragmented, largely over the last few decades, and it is now found in six main locations. It is most common in rocky, sparsely vegetated areas and open woodlands, sometimes near human habitation, within 50 kilometres of the coast.

[Image: photo.jpg]
Northern quolls, generally solitary and nocturnal, make their dens in rock crevices, tree holes or, occasionally, termite mounds. In flat, open grasslands, all males die after mating, but in rockier habitats, where the populations appear to be less stressed, males may live for two years.

The northern quoll has been described as ‘pugnacious’ in disposition and although the smallest of the four Australian quoll species, are considered the most aggressive.

Litters average six pups and are born in the dry season between June and September. The young are carried for eight to ten weeks, and weaned at about five months.

Reasons for the species' recent decline are not understood, but changing grazing and fire regimes and other impacts that degrade the habitat are the most likely causes.

In April 2003, some northern quolls were transferred to several islands off the Arnhem Land coast in the Northern Territory, to establish secure populations as a precautionary measure while the impacts of cane toads on quoll populations are further studied.
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Suicidal antechinus mystery solved

Tuesday, 8 October 2013 Rachel Sullivan

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Agile Antechinus - The study found that extreme stress causes immune system collapse, infections and internal bleeding, leading to death 

Sperm competition drives suicidal reproduction in antechinus and other marsupials, according to a new study by Australian researchers.

The research, which was published in the journal Proceedings of the National Academy of Sciences, overturns previous theories that linked the post-mating mass die-off to altruism or to food availability.

Die off in males occurs in around a fifth of all known species of insectivorous marsupials, including all 12 species of antechinus, three species of phascogale, and kalutas. Some populations of northern quoll and dibbler also experience die-offs to a lesser extent, as do some other South American species.

The study found that extreme stress, and the failure of the corticosteroid mechanism that controls it, cause immune system collapse, infections and internal bleeding, leading to death.

"We wanted to find out why semelparity (suicidal reproduction) evolved in these small insectivorous marsupials and no others," says biologist Dr Diana Fisher from the University of Queensland who led the study.

"Males of semelparous species spend most of their lives as immature animals and mature at 11 months, just before the breeding season," she adds. "They have a few other peculiarities as well: they all shut down their testes before breeding and so rely on sperm stored in the epididymis for mating, which is also lost in their urine."

"This gives them some urgency to mate, so it is no wonder that the breeding season is so frantic. Each mating can take 12 to 14 hours and they do this over and over again. Even if they survived the breeding period, they would be infertile anyway."

Going out with a bang

A previous explanation for the males die off was that it avoided competition with their offspring because of seasonal availability of food. However, Dr Fisher says the animals' lack off territoriality and promiscuous nature makes this highly unlikely.

"Males have offspring all over the place, and even if food was critically short and dying did help the next generation, this would benefit the young of others, not only their own young," she says.

To test that hypothesis, the researchers looked at life history data for 52 species of insectivorous marsupial from Australia, Papua New Guinea and South America. They found that seasonal availability of food is related to the timing and length of the breeding season, and males of species with shorter breeding seasons have lower survival, but this doesn't explain mass male die off.

"Although insect peaks vary between years -- and are likely to do so increasingly in a changing climate -- females' synchronised ovulation often occurs on the same day over a number of years and is triggered by rate of change in day length," Fisher says.

"Peaks in prey availability coincide with shorter breeding seasons, with females timing their energy intensive reproductive cycles to coincide with maximum food abundance while they raise their huge litters of offspring."

This is much more of an issue in higher latitudes than in the tropics where food is available year round, Fisher says, and the short breeding season further south places stress on males as they compete for females, however, it doesn't entirely explain suicidal reproduction.

Instead, the researchers found that females of species with the most extreme male strategy of die-off have even shorter breeding seasons than the availability of food dictates, and this time pressure imposes severe competition on males.

In response, semelparous males have large testes relative to body size that allow them to fertilise as many females as possible.

Reproductive battleground

Disintegration of their testes before mating means that males devote as much energy to competitive mating as possible. They aren't spending energy on making sperm by this stage, and use their body tissues to fuel the mating frenzy.

"The males don't engage in physical competition; instead their sperm are left to battle it out in the female's reproductive tract," Fisher says.

"Our previous work showed that females benefit from sperm competition because the best males sire more of their offspring -- antechinus males that excel at sperm competition have better offspring survival.

"This means it is actually pressure imposed by females via their reproductive timing and encouragement of sperm competition that has selected for semelparity in males. Using all their energy on the one breeding season gives males an advantage in sperm competition, so it's reproductively worthwhile for them even though they die," she adds.

"The only way for males to avoid die-off is for them to be raised independently of any females so they are never exposed to the hormones that kickstart the mating frenzy."

"But that's not much fun for them either."

Sperm competition drives the evolution of suicidal reproduction in mammals
Diana O. Fishera,1, Christopher R. Dickmanb, Menna E. Jonesc, and Simon P. Blomberga

October 7, 2013, doi: 10.1073/pnas.1310691110 
PNAS October 7, 2013

Suicidal reproduction (semelparity) has evolved in only four genera of mammals. In these insectivorous marsupials, all males die after mating, when failure of the corticosteroid feedback mechanism elevates stress hormone levels during the mating season and causes lethal immune system collapse (die-off). We quantitatively test and resolve the evolutionary causes of this surprising and extreme life history strategy. We show that as marsupial predators in Australia, South America, and Papua New Guinea diversified into higher latitudes, seasonal predictability in abundance of their arthropod prey increased in multiple habitats. More-predictable prey peaks were associated with shorter annual breeding seasons, consistent with the suggestion that females accrue fitness benefits by timing peak energy demands of reproduction to coincide with maximum food abundance. We demonstrate that short mating seasons intensified reproductive competition between males, increasing male energy investment in copulations and reducing male postmating survival. However, predictability of annual prey cycles alone does not explain suicidal reproduction, because unlike insect abundance, peak ovulation dates in semelparous species are often synchronized to the day among years, triggered by a species-specific rate of change of photoperiod. Among species with low postmating male survival, we show that those with suicidal reproduction have shorter mating seasons and larger testes relative to body size. This indicates that lethal effort is adaptive in males because females escalate sperm competition by further shortening and synchronizing the annual mating period and mating promiscuously. We conclude that precopulatory sexual selection by females favored the evolution of suicidal reproduction in mammals. 
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Comparative Bite Force/Stress Analysis

Virtual Reconstruction and Prey Size Preference in the Mid Cenozoic Thylacinid, Nimbacinus dicksoni (Thylacinidae, Marsupialia)

Marie R. G. Attard, William C. H. Parr, Laura A. B. Wilson, Michael Archer, Suzanne J. Hand, Tracey L. Rogers, Stephen Wroe
Published: April 09, 2014
DOI: 10.1371/journal.pone.0093088

Thylacinidae is an extinct family of Australian and New Guinean marsupial carnivores, comprizing 12 known species, the oldest of which are late Oligocene (~24 Ma) in age. Except for the recently extinct thylacine (Thylacinus cynocephalus), most are known from fragmentary craniodental material only, limiting the scope of biomechanical and ecological studies. However, a particularly well-preserved skull of the fossil species Nimbacinus dicksoni, has been recovered from middle Miocene (~16-11.6 Ma) deposits in the Riversleigh World Heritage Area, northwestern Queensland. Here, we ask whether N. dicksoni was more similar to its recently extinct relative or to several large living marsupials in a key aspect of feeding ecology, i.e., was N. dicksoni a relatively small or large prey specialist. To address this question we have digitally reconstructed its skull and applied three-dimensional Finite Element Analysis to compare its mechanical performance with that of three extant marsupial carnivores and T. cynocephalus. Under loadings adjusted for differences in size that simulated forces generated by both jaw closing musculature and struggling prey, we found that stress distributions and magnitudes in the skull of N. dicksoni were more similar to those of the living spotted-tailed quoll (Dasyurus maculatus) than to its recently extinct relative. Considering the Finite Element Analysis results and dental morphology, we predict that N. dicksoni likely occupied a broadly similar ecological niche to that of D. maculatus, and was likely capable of hunting vertebrate prey that may have exceeded its own body mass.

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TABLE 1: Predicted body mass and masticatory muscle forces for modeled dasyuromorphians.

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FIGURE 3: Von Mises stress under a bilateral canine bite in lateral view.
The models are subjected to a load applied to both canines, with bite force scaled based on theoretical body mass. Species modeled were (A) Dasyurus hallucatus, (B) Dasyurus maculatus, © Sarcophilus harrisii, (D) Nimbacinus dicksoni and (E) Thylacinus cynocephalus. White colored regions of the skull represent VM stress above 10 MPa. (F) Distribution of von Mises stress was measured from anterior to posterior along the mandible.

[Image: journal.pone.0093088.g004]
FIGURE 4: Von Mises stress under a bilateral canine bite in dorsal view.
The models are subjected to a load applied to both canines, with bite force scaled based on theoretical body mass. Species modeled were (A) Dasyurus hallucatus, (B) Dasyurus maculatus, © Sarcophilus harrisii, (D) Nimbacinus dicksoni and (E) Thylacinus cynocephalus. White colored regions of the skull represent VM stress above 10 MPa. (F) Distribution of von Mises stress was measured from anterior to posterior along the mid-sagittal plane.

[Image: journal.pone.0093088.g005]
FIGURE 5: Von Mises stress under extrinsic loads in lateral view.
The models are subjected to various loads applied to the canines, including a (A, E, I, M, Q) lateral shake, (B, F, J, N, R) axial twist, (C, G, K, O, S) pullback and (D, H, L, P, T) dorsoventral. The force applied was equivalent to 100 times the animal's estimated body mass for an axial twist, and 10 times the animal's estimated body mass for a lateral shake, pullback and dorsoventral shake. Species compared were (A–D) Dasyurus hallucatus, (E–H) Dasyurus maculatus, (I–L) Sarcophilus harrisii, (M–P) Nimbacinus dicksoni and (Q–T) Thylacinus cynocephalus. White colored regions of the skull represent VM stress above 10 MPa. Distribution of von Mises (VM) stress was measured from anterior to posterior along the mandible for a (U) lateral shake, (V) axial twist, (W) pullback and (X) dorsoventral.

[Image: journal.pone.0093088.g006]
FIGURE 6: Von Mises stress under extrinsic loads in dorsal view.
The models are subjected to various loads applied to the canines, including a (A, E, I, M, Q) lateral shake, (B, F, J, N, R) axial twist, (C, G, K, O, S) pullback and (D, H, L, P, T) dorsoventral. The force applied was equivalent to 100 times the animal's estimated body mass for an axial twist, and 10 times the animal's estimated body mass for a lateral shake, pullback and dorsoventral shake. Species compared were (A–D) Dasyurus hallucatus, (E–H) Dasyurus maculatus, (I–L) Sarcophilus harrisii, (M–P) Nimbacinus dicksoni and (Q–T) Thylacinus cynocephalus. White colored regions of the skull represent VM stress above 10 MPa. Distribution of von Mises (VM) stress was measured from anterior to posterior along the mid-sagittal plane for a (U) lateral shake, (V) axial twist, (W) pullback and (X) dorsoventral.

Differences in biomechanical performance between the three extant dasyurids included in this study appear consistent with their respective known feeding behaviors. Dasyurus hallucatus showed comparatively higher levels of stress in most simulations than S. harrisii and D. maculatus. Dasyurus hallucatus eats invertebrates and other relatively small prey, which may not require adaptation to sustain the full range of extrinsic loads simulated here. This species shows particularly high VM stress in axial twisting, especially in contrast to S. harrisii However, it performs relatively well under pull-back loading, which may be linked to a capacity for pulling invertebrates from the ground. Observational studies on wild D. hallucatus will be required to confirm the functional role of their skull in prey acquisition. Future work on the comparative musculoskeletal anatomy and collection of in vivo or ex vivo biomechanical data of the extant species would likely improve the predictive power of current bite force and muscle force estimations. Overall consistencies found between known prey size and biomechanical performance for extant dasyuromorphians underscore the potential value of projections based on comparative FEA for extinct/fossil taxa.

Our comparative biomechanical modeling of dasyuromorphian skulls suggests considerable differences in predatory behaviors between the two thylacinids considered here. Our 3D based results indicate that the Oligocene to Miocene N. dicksoni had a high bite force for its size, comparable to that of extant dasyurids known to take relatively large prey, D. maculatus and S. harrisii . In light of similar levels of ‘carnassialization’ (development of relatively long, high amplitude vertical shearing crests) in the cheektooth dentition with D. maculatus, and a lack of obvious dental specialization consistent with regular bone-cracking, our results suggest a predominantly carnivorous diet for N. dicksoni that may have included relatively large prey. Dasyurus maculatus are opportunistic hunters, varying their diet in response to environmental disturbances and short-term fluctuations in prey abundance. They will prey on vertebrate species up to and sometimes exceeding their own body mass. Prey includes bandicoots, smaller dasyurids, possums, smaller macropodoids, snakes, lizards, birds and frogs, as well as invertebrates. Potential prey for a fox-sized thylacinid living in the closed forest communities of Riversleigh likely included many small to medium-size birds, frogs, lizards and snakes, as well as a wide range of marsupials, including bandicoots (peramelemorphians), dasyurids (dasyuromorphians), kangaroos (macropodoids), thingodontans (yalkiparidontians), marsupial moles (notoryctemorphians) and wombats (vombatoids).

Although our FEA results for N. dicksoni suggest a capacity to kill prey approaching or exceeding its own body mass, its prey range may have been limited by competition with sympatric carnivores. The extent of niche overlap and competition within this ancient, medium-large sized carnivore community may have been partially alleviated by occupying different habitats and specializing in different hunting strategies. The recovery of a near complete skeleton of N. dicksoni will provide further information on the locomotion and predatory behavior based on postcranial material; for example, was N. dicksoni as arboreal as the extant D. maculatus?

Differences in mechanical performance suggest that T. cynocephalus is unusual relative to other dasyuromorphians, including, N. dicksoni, as indicated by distinctly higher VM stresses than all other species in response to each loading case. Thylacinus cynocephalus, in contrast to N. dicksoni, has completely lost the metaconid on the lower molars and has a proportionately much larger postmetacrista on the upper molars. On the basis of traditional beam theory we predicted that taxa with longer rostra would exhibit higher stress , as evident in the long-snouted T. cynocephalus relative to shorter-snouted dasyuromorphians. Differences between T. cynocephalus and other species were also significant for three out of five simulations examined after conservative Bonferroni correction for multiple testing. These results further support the contention by Attard et al. that niche breadth in T. cynocephalus may have been more limited and that it likely preyed on relatively small to medium-sized vertebrates such as wallabies, possums and bandicoots.

Although measures of skull performance in response to forces imposed by struggling prey revealed closer similarity between the fossil thylacinid N. dicksoni and large extant carnivorous dasyurids, than with T. cynocephalus, there were differences. Our reconstruction suggests that the TMJ was more elevated in N. dicksoni than in D. maculatus, and higher relative to the height of the cheektooth row. The TMJ is a complex joint and is important for occlusion and mastication. The position of the TMJ can influence bite strength and muscle activation . The position of the TMJ along the anterior-posterior axis tends to lie closer to the plane of the tooth row in carnivorous taxa. Conclusive determination of the precise position and morphology of the TMJ in N. dicksoni must await the discovery of more complete cranial material.

Morphological evidence from past studies further demonstrates diversity within this family. The smallest thylacinid, Muribacinus gadiyuli, is believed to have fed on relatively small vertebrates and invertebrates because it lacks a number of dental features present in large prey specialists (e.g., robust protoconids and brachycephalization) such as similarly sized D. maculatus. The variety of feeding behaviors among thylacinids may have helped facilitate their co-existence within different ecological niches that were later filled by diversifying carnivorous dasyurids.;jsessionid=BD11A1EFAC62DC25EA00D48A6F32A50A
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Species found to lose fear of predators after 13 generations of protective isolation

June 6, 2018 by Bob Yirka, report

A trio of researchers from the University of Melbourne and the University of Life Science, Sydney, has found an isolated mammal species that lost its fear of predators in just 13 generations. In their paper published in the journal Biology Letters, Chris Jolly, Jonathan Webb and Ben Phillips describe their study of protected northern quolls living in Australia and what they found.

As humans encroach on territory occupied by other species, those other species lose out. Often, the result is endangerment or extinction. That has been the case for northern quolls, which once inhabited large parts of northern Australia. After humans arrived, their numbers declined sharply due mostly to the introduction of invasive cane toads. To prevent their extinction, environmentalists captured several of them and released them on two small islands off the coast of Australia. That effort, it seemed, was a remarkable success as quoll populations soon soared on the islands. Pleased with their results, environmentalist tried to capitalize on their success by capturing a large number of the creatures and placing them back in their native environment. Unfortunately, the experiment did not go as planned. Over the span of just 21 months, most of the quolls were gone. This time, it was not poisonous toads causing their deaths, it was dingoes capturing and eating them. This came as a surprise to the team, because prior to the arrival of humans, quolls were able to survive in territory occupied by dingoes. They did so, the researchers note, by hiding from them.

To better understand why the transplanted quolls fell victim to the dingoes, the researchers captured several of them from populations on the protected island and from locations where they had survived on the mainland. All of the quolls were put into cages where they could access a food source only by poking their snout through a hole in a box. Some of the holes were lined with dingo fur, or cat fur. In studying how the quolls behaved, the team found that those quolls from the protected island had no fear of sticking their snouts through predator-scented holes, showing that they had lost their fear of them—in just 13 generations.

Journal Reference:
Chris J. Jolly et al. The perils of paradise: an endangered species conserved on an island loses antipredator behaviours within 13 generations, Biology Letters (2018). DOI: 10.1098/rsbl.2018.0222

When imperilled by a threatening process, the choice is often made to conserve threatened species on offshore islands that typically lack the full suite of mainland predators. While keeping the species extant, this releases the conserved population from predator-driven natural selection. Antipredator traits are no longer maintained by natural selection and may be lost. It is implicitly assumed that such trait loss will happen slowly, but there are few empirical tests. In Australia, northern quolls (Dasyurus hallucatus) were moved onto a predator-free offshore island in 2003 to protect the species from the arrival of invasive cane toads on the mainland. We compared the antipredator behaviours of wild-caught quolls from the predator-rich mainland with those from this predator-free island. We compared the responses of both wild-caught animals and their captive-born offspring, to olfactory cues of two of their major predators (feral cats and dingoes). Wild-caught, mainland quolls recognized and avoided predator scents, as did their captive-born offspring. Island quolls, isolated from these predators for only 13 generations, showed no recognition or aversion to these predators. This study suggests that predator aversion behaviours can be lost very rapidly, and that this may make a population unsuitable for reintroduction to a predator-rich mainland. 
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