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Mountain Zebra - Equus zebra
#1
Mountain Zebra - [i]Equus zebra[/i]

[Image: Cape-mountain-zebra-rear-view.jpg]

Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Family: Equidae
Genus: Equus
Subgenus: Hippotigris
Species: Equus zebra

The mountain zebra (Equus zebra) is a threatened species of equid native to south-western Angola, Namibia and South Africa. It has two subspecies:
  • Cape Mountain Zebra (Equus zebra zebra)

  • Hartmann's Mountain Zebra (Equus zebra hartmannae)
though it has been suggested these should be considered separate species.

[Image: Cape-mountain-zebra.jpg]

Taxonomy
In 2004, C. P. Groves and C. H. Bell investigated the taxonomy of the zebras (genus Equus, subgenus Hippotigris). They concluded that the Cape mountain zebra (Equus zebra zebra) and Hartmann's mountain zebra (Equus zebra hartmannea) are distinct, and suggested that the two would be better classified as separate species, Equus zebra and Equus hartmannae.
However, in a sexual genetic study that included 295 mountain zebra specimens, Moodley and Harley (2005) found no genetic evidence to regard the two mountain zebra taxa as anything more than different populations of a single species. They concluded that the Cape mountain zebra and Hartmann's mountain zebra should remain as subspecies.
The third edition of Mammal Species of the World (2005) lists the mountain zebra as a single species (Equus zebra) with two subspecies.

[Image: Cape-mountain-zebras.jpg]

Appearance
Like all extant zebras, it is boldly striped in black and white and no two individuals look exactly alike. The stripes can be either black or dark brown and white. Their stripes cover their whole bodies except for their bellies. The mountain zebra also has a dewlap.
Adult mountain zebras have a head-and-body length of 2.1 to 2.7 m (6 ft 11 in to 8 ft 10 in) and a tail of 40 to 55 cm (16 to 22 in) long. Shoulder height ranges from 1.1 to 1.5 m (3 ft 7 in to 4 ft 11 in). They weigh from 204 to 372 kg (450 to 820 lb). Groves and Bell found that the Cape mountain zebra exhibits sexual dimorphism, with larger females than males, while the Hartmann's mountain zebra does not. The black stripes of Hartmann's mountain zebra are thin with much wider white interspaces, while this is the opposite in the Cape mountain zebra.

[Image: 440px-Mountain_Zebra_Distributions.jpg]
Range map of Equus zebra zebra and Equus zebra hartmannae

Habitat
Mountain zebras are found on mountain slopes, open grasslands, woodlands and areas with sufficient vegetation.

Ecology
Mountain zebras live in hot, dry, rocky, mountainous and hilly habitats. They prefer slopes and plateaus and can be found as high as 1,000 metres (3,300 ft) above sea level, although they do migrate lower in the winter season. Their diet consists of tufted grass, bark, leaves, buds, fruit, and roots. They often dig for ground water.
The Cape mountain zebra and the Hartmann's mountain zebra are now allopatric, meaning that their present ranges are nonoverlapping. They are therefore unable to crossbreed. This is a result of their extermination by hunting in the Northern Cape Province of South Africa. Historically mountain zebras could be found across the entire length of the mountainous escarpment that runs along the west coast of southern Africa as well as in the fold mountain region in southern South Africa.

[Image: Cape-mountain-zebra-feeding.jpg]

Life cycle
The mountain zebras form small family groups consisting of a single stallion, one, two, or several mares, and their recent offspring. Bachelor males live in separate groups and attempt to abduct young mares and are opposed by the stallion. Mountain zebra groups do not aggregate into large herds like Plains zebras.
Mares give birth to at least one foal every 12 months. The foal feeds on its mothers milk for a year and then starts eating grass, tree leaves, etc. After a year or 3, a male foal must leave the herd and form a new one. If the colt is too stubborn, it will stay and try a challenging fight with the stallion or lead mare.

Threats
The main threats to the species are from loss of habitat to agriculture, hunting and persecution. 

[Image: Cape-mountain-zebra-running.jpg]

Conservation
The species is listed as Vulnerable under the IUCN Red List. The Cape mountain zebra was hunted to near extinction with less than 100 individuals by the 1930s. In 1998 it was estimated that approximately 1,200 Cape mountain zebra survived, of which around 542 occurred in national parks, 491 in provincial nature reserves, and 165 in other reserves. However the population has increased to about over 2,700 in the wild due to conservation efforts. Both mountain zebra subspecies are currently protected in national parks but are still threatened. There is a European Zoo's Endangered Species Program for this zebra as well as co-operative management of zoo populations worldwide.
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#2
Zebra stripes mystery 'explained'

By Ella Davies
Reporter, BBC Nature
17 December 2013 Last updated at 03:15

[Image: _71767976_img_6381.jpg]

Zebras' bold stripes protect the animals by masking their movements, according to a study.

The conspicuous colours do not blend in to the background and scientists have theorised they developed to dazzle predators.

Using computer models, researchers confirmed the markings create optical illusions when the animals move.

They suggest this confusion helps to protect the animals from both big cats and tiny insects.

The research, conducted by researchers from the University of Queensland, Australia, is published in the journal Zoology.

"Zebra stripes have long confused evolutionary biologists, right back to Darwin and Wallace," said lead author Dr Martin How.

[Image: _71767978_img_7018.jpg]

"Previous theories for the function of these stripes include social communication signals, camouflage at dusk or dawn in grassy habitats, and the so-called 'dazzle' effect when being pursued by predators or blood sucking insects."

To test this latest theory that the patterns confuse predators and pests, Dr How and colleague Prof Johannes Zanker from Royal Holloway, University of London, analysed photographs and video footage of zebras.

Computer models that tracked the appearance of the patterns revealed that they worked as optical illusions to provide "misleading information".

Humans and a wide range of animals share what scientists refer to as "motion detection mechanisms": neural circuits which process the direction something is moving based on how its contours appear.

One of the best known examples of an illusion that confuses this mechanism is the barber-pole effect, where the spiral of stripes on a vertical pole appears to move upwards when the pole spins.

The wagon-wheel effect is a further example, where the spokes of a wagon wheel turn clockwise but when a particular speed is reached, the wheel appears to turn anti-clockwise.

According to Dr How, zebra stripes capitalise on this type of illusion to help protect the animals.

He explained that the broad diagonal stripes on a zebra's flank and the narrower vertical stripes on its back and neck give unexpected motion signals that confuse viewers, particularly in a herd of zebras.

"We suggest that these illusions cause pests and predators to mistake the zebra's movement direction, causing biting insects to abort their landing manoeuvres and chasing predators to mistime their attacks," said Dr How.

"The results have implications for the study of patterning in animals - there are many other species such as humbug damselfish or banded snakes that use apparently conspicuous black and white stripe body patterns.

The results also might help us understand how similar camouflage might function in man-made situations, such as the large-scale 'dazzle' camouflage patterns used on battleships."

http://www.bbc.co.uk/nature/25260311




Motion camouflage induced by zebra stripes
Martin J. Howa, Johannes M. Zankerb

Abstract
The functional significance of the zebra coat stripe pattern is one of the oldest questions in evolutionary biology, having troubled scientists ever since Charles Darwin and Alfred Russel Wallace first disagreed on the subject. While different theories have been put forward to address this question, the idea that the stripes act to confuse or ‘dazzle’ observers remains one of the most plausible. However, the specific mechanisms by which this may operate have not been investigated in detail. In this paper, we investigate how motion of the zebra's high contrast stripes creates visual effects that may act as a form of motion camouflage. We simulated a biologically motivated motion detection algorithm to analyse motion signals generated by different areas on a zebra's body during displacements of their retinal images. Our simulations demonstrate that the motion signals that these coat patterns generate could be a highly misleading source of information. We suggest that the observer's visual system is flooded with erroneous motion signals that correspond to two well-known visual illusions: (i) the wagon-wheel effect (perceived motion inversion due to spatiotemporal aliasing); and (ii) the barber-pole illusion (misperceived direction of motion due to the aperture effect), and predict that these two illusory effects act together to confuse biting insects approaching from the air, or possibly mammalian predators during the hunt, particularly when two or more zebras are observed moving together as a herd.

http://www.sciencedirect.com/science/article/pii/S0944200613000974
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#3
^A different theory!

Scientists solve the riddle of zebras' stripes: Those pesky bugs

Date: April 1, 2014
Source: University of California - Davis
Summary:
Why zebras have black and white stripes is a question that has intrigued scientists and spectators for centuries. Scientists now examined this riddle systematically.

[Image: 140401112111_1_540x360.jpg]
UC Davis scientists have learned why zebras, like these plains zebras in Katavi National Park, Tanzania, have stripes.

Why zebras have black and white stripes is a question that has intrigued scientists and spectators for centuries. A research team led by the University of California, Davis, has now examined this riddle systematically. Their answer is published April 1 in the online journal Nature Communications.
The scientists found that biting flies, including horseflies and tsetse flies, are the evolutionary driver for zebra's stripes. Experimental work had previously shown that such flies tend to avoid black-and-white striped surfaces, but many other hypotheses for zebra stripes have been proposed since Alfred Russel Wallace and Charles Darwin debated the problem 120 years ago.
These include:
  • A form of camouflage

  • Disrupting predatory attack by visually confusing carnivores

  • A mechanism of heat management

  • Having a social function

  • Avoiding ectoparasite attack, such as from biting flies
The team mapped the geographic distributions of the seven different species of zebras, horses and asses, and of their subspecies, noting the thickness, locations, and intensity of their stripes on several parts of their bodies. Their next step was to compare these animals' geographic ranges with different variables, including woodland areas, ranges of large predators, temperature, and the geographic distribution of glossinid (tsetse flies) and tabanid (horseflies) biting flies. They then examined where the striped animals and these variables overlapped.
After analyzing the five hypotheses, the scientists ruled out all but one: avoiding blood-sucking flies.
"I was amazed by our results," said lead author Tim Caro, a UC Davis professor of wildlife biology. "Again and again, there was greater striping on areas of the body in those parts of the world where there was more annoyance from biting flies."
While the distribution of tsetse flies in Africa is well known, the researchers did not have maps of tabanids (horseflies, deer flies). Instead, they mapped locations of the best breeding conditions for tabanids, creating an environmental proxy for their distributions. They found that striping is highly associated with several consecutive months of ideal conditions for tabanid reproduction.
Why would zebras evolve to have stripes whereas other hooved mammals did not? The study found that, unlike other African hooved mammals living in the same areas as zebras, zebra hair is shorter than the mouthpart length of biting flies, so zebras may be particularly susceptible to annoyance by biting flies.
"No one knew why zebras have such striking coloration," Caro said. "But solving evolutionary conundrums increases our knowledge of the natural world and may spark greater commitment to conserving it."
Yet in science, one solved riddle begets another: Why do biting flies avoid striped surfaces? Caro said that now that his study has provided ecological validity to the biting fly hypothesis, the evolutionary debate can move from why zebras have stripes to what prevents biting flies from seeing striped surfaces as potential prey, and why zebras are so susceptible to biting fly annoyance.

http://www.sciencedaily.com/releases/2014/04/140401112111.htm



Journal Reference:
Tim Caro, Amanda Izzo, Robert C. Reiner, Hannah Walker, Theodore Stankowich. The function of zebra stripes. Nature Communications, 2014; 5 DOI: 10.1038/ncomms4535

Abstract
Despite over a century of interest, the function of zebra stripes has never been examined systematically. Here we match variation in striping of equid species and subspecies to geographic range overlap of environmental variables in multifactor models controlling for phylogeny to simultaneously test the five major explanations for this infamous colouration. For subspecies, there are significant associations between our proxy for tabanid biting fly annoyance and most striping measures (facial and neck stripe number, flank and rump striping, leg stripe intensity and shadow striping), and between belly stripe number and tsetse fly distribution, several of which are replicated at the species level. Conversely, there is no consistent support for camouflage, predator avoidance, heat management or social interaction hypotheses. Susceptibility to ectoparasite attack is discussed in relation to short coat hair, disease transmission and blood loss. A solution to the riddle of zebra stripes, discussed by Wallace and Darwin, is at hand.

http://www.nature.com/ncomms/2014/140401/ncomms4535/full/ncomms4535.html
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#4
Another theory:

Zebra stripes not for camouflage, new study finds

Date: January 22, 2016
Source: University of California - Davis
Summary:
Looking through the eyes of zebra predators, researchers found no evidence supporting the notion that zebras' black and white stripes are for protective camouflage or that they provide a social advantage.

[Image: 160122170837_1_900x600.jpg]
A zebra grazing on the grassy plains gazes at the researchers' chart used for color-calibrating images. (Tim Caro/UC Davis)
Credit: Tim Caro/UC Davis

If you've always thought of a zebra's stripes as offering some type of camouflaging protection against predators, it's time to think again, suggest scientists at the University of Calgary and UC Davis.

Findings from their study will be published Friday, Jan. 22, 2016 in the journal PLOS ONE.

"The most longstanding hypothesis for zebra striping is crypsis, or camouflaging, but until now the question has always been framed through human eyes," said the study's lead author Amanda Melin, an assistant professor of biological anthropology at the University of Calgary, Canada.

"We, instead, carried out a series of calculations through which we were able to estimate the distances at which lions and spotted hyenas, as well as zebras, can see zebra stripes under daylight, twilight, or during a moonless night.

Melin conducted the study with Tim Caro, a UC Davis professor of wildlife biology. In earlier studies, Caro and other colleagues have provided evidence suggesting that the zebra's stripes provide an evolutionary advantage by discouraging biting flies, which are natural pests of zebras.

In the new study, Melin, Caro and colleagues Donald Kline and Chihiro Hiramatsu found that stripes cannot be involved in allowing the zebras to blend in with the background of their environment or in breaking up the outline of the zebra, because at the point at which predators can see zebras stripes, they probably already have heard or smelled their zebra prey.

"The results from this new study provide no support at all for the idea that the zebra's stripes provide some type of anti-predator camouflaging effect," Caro said. "Instead, we reject this long-standing hypothesis that was debated by Charles Darwin and Alfred Russell Wallace."

New findings:

To test the hypothesis that stripes camouflage the zebras against the backdrop of their natural environment, the researchers passed digital images taken in the field in Tanzania through spatial and color filters that simulated how the zebras would appear to their main predators -- lions and spotted hyenas -- as well as to other zebras.

They also measured the stripes' widths and light contrast, or luminance, in order to estimate the maximum distance from which lions, spotted hyenas and zebras could detect stripes, using information about these animals' visual capabilities.

They found that beyond 50 meters (about 164 feet) in daylight or 30 meters (about 98 feet) at twilight, when most predators hunt, stripes can be seen by humans but are hard for zebra predators to distinguish. And on moonless nights, the stripes are particularly difficult for all species to distinguish beyond 9 meters (about 29 feet.) This suggests that the stripes don't provide camouflage in woodland areas, where it had earlier been theorized that black stripes mimicked tree trunks and white stripes blended in with shafts of light through the trees.

And in open, treeless habitats, where zebras tend to spend most of their time, the researchers found that lions could see the outline of striped zebras just as easily as they could see similar-sized, prey with fairly solid-colored hides, such as waterbuck and topi and the smaller impala. It had been earlier suggested that the striping might disrupt the outline of zebras on the plains, where they might otherwise be clearly visible to their predators.

Stripes also not for social purposes:

In addition to discrediting the camouflaging hypothesis, the study did not yield evidence suggesting that the striping provides some type of social advantage by allowing other zebras to recognize each other at a distance.

While zebras can see stripes over somewhat further distances than their predators can, the researchers also noted that other species of animals that are closely related to the zebra are highly social and able to recognize other individuals of their species, despite having no striping to distinguish them.

Story Source: University of California - Davis. "Zebra stripes not for camouflage, new study finds." ScienceDaily. www.sciencedaily.com/releases/2016/01/160122170837.htm (accessed January 22, 2016).




Journal Reference:
Amanda D. Melin, Donald W. Kline, Chihiro Hiramatsu, Tim Caro. Zebra Stripes through the Eyes of Their Predators, Zebras, and Humans. PLOS ONE, 2016; 11 (1): e0145679 DOI: 10.1371/journal.pone.0145679

Abstract
The century-old idea that stripes make zebras cryptic to large carnivores has never been examined systematically. We evaluated this hypothesis by passing digital images of zebras through species-specific spatial and colour filters to simulate their appearance for the visual systems of zebras’ primary predators and zebras themselves. We also measured stripe widths and luminance contrast to estimate the maximum distances from which lions, spotted hyaenas, and zebras can resolve stripes. We found that beyond ca. 50 m (daylight) and 30 m (twilight) zebra stripes are difficult for the estimated visual systems of large carnivores to resolve, but not humans. On moonless nights, stripes are difficult for all species to resolve beyond ca. 9 m. In open treeless habitats where zebras spend most time, zebras are as clearly identified by the lion visual system as are similar-sized ungulates, suggesting that stripes cannot confer crypsis by disrupting the zebra’s outline. Stripes confer a minor advantage over solid pelage in masking body shape in woodlands, but the effect is stronger for humans than for predators. Zebras appear to be less able than humans to resolve stripes although they are better than their chief predators. In conclusion, compared to the uniform pelage of other sympatric herbivores it appears highly unlikely that stripes are a form of anti-predator camouflage.

[Image: journal.pone.0145679.g001]
Fig 1. Photographs of a (a) plains, (b) mountain, and © Grevy’s zebra, and (d) African wild ass in the Tierpark Zoo, Berlin.

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0145679 
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#5
Zebra scat science improves conservation efforts

Date: November 1, 2017
Source: University of Manchester
Summary:
How can zebra excrement tell us what an animal's response to climate change and habitat destruction will be? That is what scientists have been investigating in South Africa. Together the team have been using zebra stools to understand how challenges or 'stressors', such as the destruction and breakup of habitats, impact on populations of South Africa's Cape mountain zebra.

[Image: 171101102640_1_900x600.jpg]
Cape Mountain Zebra in South Africa.
Credit: Jessica Lea from The University of Manchester

How can Zebra excrement tell us what an animal's response to climate change and habitat destruction will be?

That is what scientists from The University of Manchester and Chester Zoo have been investigating in South Africa. Together the team have been using zebra stools to understand how challenges or 'stressors', such as the destruction and breakup of habitats, impact on populations of South Africa's Cape mountain zebra.

To measure 'stress' levels of the animals the scientists have been analysing glucocorticoid hormones in the Cape zebra's droppings. Glucocorticoid hormones are a group of steroid hormones that help regulate the 'flight or fight' stress response in animals.

The research found that zebras are facing multiple challenges, including poor habitat and gender imbalances, which are likely to compromise their health, have repercussions for their reproduction and, ultimately, a population's long term survival.

Dr Susanne Shultz, the senior author from the School of Earth and Environmental Sciences (SEES) at Manchester, explains: 'Faecal hormone measurements are easy to collect without disturbing the animals and provide a window into the chronic stress animals are experiencing. Using these indicators we can establish the health of both individuals and populations.'

The team have used a 'macrophysiological approach' for the first time ever to evaluate the effectiveness of an ongoing conservation plan. A macrophysiological approach involves comparing animal responses in different nature reserves or geographical regions. By evaluating patterns of stress on a large scale, at-risk populations can be identified as their profile will differ from healthy populations.

The researchers also found that using physiological biomarkers, such as hormones from droppings, is an effective way of evaluating the impact of ecological and demographic factors on animal populations. This approach could also tell conservationists how other animals and species might respond to future environmental changes and stressors.

Dr Sue Walker, Head of Applied Science at Chester zoo, said: 'Zoos specialise in population management and have developed a wide range of innovative techniques to monitor the species under their care. This project is a fantastic example of how we can use these knowledge and skills to also help the conservation of wild animals threatened with extinction.'

As well as using this new approach the particular species of the Zebra was also important. Dr Jessica Lea, from SEES and the paper's lead author, added: 'The Cape mountain zebra is an ideal model species to assess because it has undergone huge ecological and demographic changes in the recent years.

'Following a massive population decline, they have been actively conserved for the past several decades. The information available on their recovery means we can measure the impacts of both environment and social factors on population health.'

Combining SEES's knowledge in macroecology with Chester Zoo's expertise in wildlife physiology allowed the team to gain crucial insights into the Cape Mountain zebra ecology. This then translated into practical applied conservation management initiatives to support the species.

Dr Shultz added: 'Understanding the factors leading to global biodiversity loss is a major societal challenge. In an ever-changing environment, new problems arise quickly so it is essential we use evidence-based methods to continually evaluate the effectiveness of conservation projects.'

Notes

* The Cape mountain zebra are found in the Eastern and Western Cape provinces of South Africa. The majority of their historic and current range is in the Cape Floristic Region, but also extends northeast into Nama-Karoo, thicket and grassland habitats and northwest into the Succulent Karoo biome.

* The Cape Floristic Region has a Mediterranean climate and is known for its unusually high biodiversity and proportion of endemic species, particularly flora.

* For this research seven populations were sampled. These were from Bakkrans Nature Reserve, Camdeboo National Park, De Hoop Nature Reserve, Gamkaberg Nature Reserve, Mount Camdeboo Private Game Reserve and Swartberg Private Game Reserve and Welgevonden Game Farm

Story Source: University of Manchester. "Zebra scat science improves conservation efforts." ScienceDaily. www.sciencedaily.com/releases/2017/11/171101102640.htm (accessed November 5, 2017).




Journal Reference:
Jessica M. D. Lea, Susan L. Walker, Graham I. H. Kerley, John Jackson, Shelby C. Matevich, Susanne Shultz. Non-invasive physiological markers demonstrate link between habitat quality, adult sex ratio and poor population growth rate in a vulnerable species, the Cape mountain zebra. Functional Ecology, 2017; DOI: 10.1111/1365-2435.13000

Abstract
Effective conservation and species management require an understanding of the causes of poor population growth. Conservation physiology uses biomarkers to identify factors that contribute to low individual fitness and population declines. Building on this, macrophysiology can use the same markers to assess how individual physiology varies with different ecological or demographic factors over large temporal and spatial scales.
Here, we use a macrophysiological approach to identify the ecological and demographic correlates of poor population growth rates in the Cape mountain zebra metapopulation. We use two non-invasive biomarkers: faecal glucocorticoids as a measure of chronic stress, and faecal androgens as an indicator of male physiological status.
We found that faecal glucocorticoid concentrations were highest in the spring prior to summer rainfall, and were elevated in individuals from populations associated with low-quality habitat (lower grass abundance). In addition, faecal androgen concentrations were higher in populations with a high proportion of non-breeding stallions (where male:female adult sex ratios exceed 2:1) suggesting sex ratio imbalances may intensify male competition. Finally, population growth rate was negatively associated with faecal glucocorticoid concentrations and female fecundity was negatively associated with faecal androgens, indicating a relationship between hormone profiles and fitness.
Together, our results provide cross-population evidence for how poor population growth rates in Cape mountain zebra can be linked to individual physiological biomarkers. More broadly, we advocate physiological biomarkers as indicators of population viability, and as a way to evaluate the impact of variable ecological and demographic factors. In addition, conservation physiology can be used to assess the efficacy of management interventions for this subspecies, and this approach could inform models of species’ responses to future environmental change.


http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13000/abstract;jsessionid=E4D3051F43CC93BE9B3B4DB96D40259E.f02t04 
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