How female hyaenas came to dominate males

November 19, 2018, Forschungsverbund Berlin e.V. (FVB)

In most animal societies, members of one sex dominate those of the other. Is this, as widely believed, an inevitable consequence of a disparity in strength and ferocity between males and females? Not necessarily. A new study on wild spotted hyaenas shows that in this social carnivore, females dominate males because they can rely on greater social support than males, not because they are stronger or more competitive in any other individual attribute. The main reason for females having, on average, more social support than males is that males are more likely to disperse and that dispersal disrupts social bonds. The study by scientists of the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW, Germany) and the Institut des Sciences de l'Evolution de Montpellier (ISEM, France) was published in the journal Nature Ecology & Evolution.

Spotted hyaena females are often portrayed as archetypes of powerful and ferocious females. They are on average heavier than the males, have highly masculinised outer genitalia (a 'pseudo-penis' and a 'pseudo-scrotum'), and usually occupy the highest position in the society. But according to the new study, it is not their manliness that allows them to dominate males. "When two hyaenas squabble, the one that can rely on greater social support wins, irrespective of sex, body mass or aggressiveness," explains Oliver Hoener, head of the Ngorongoro Hyena Project of the Leibniz-IZW. Differences in social support between two individuals correctly predicted who will be the dominant in almost all encounters and in all contexts—between natives and immigrants, members of the same and different clans, residents and intruders, and individuals of the same and opposite sex. Female dominance thus emerges from females being more likely to receive greater social support than males. "What is so fascinating is that it all works without any direct involvement of other hyaenas," says Colin Vullioud, Hoener's colleague at Leibniz-IZW and first author of the study. "In the end, it's all about assertiveness and how confident a hyaena is of receiving support if needed."

For their study, the scientists analysed the outcome of 4133 agonistic interactions between 748 hyaenas from eight different clans monitored for 21 years in the Ngorongoro Crater in Tanzania. To estimate potential social support, they developed an algorithm that predicted for each clan member, which of two interacting hyaenas it would support; this algorithm was derived from behavioural observations of social support and relatedness estimates based on one of the most comprehensive pedigrees of a free-ranging mammal. "To tease apart the effects of social support and intrinsic attributes such as body mass, one needs to evaluate each effect while controlling for the presence of the other" explains Francois Rousset (ISEM), who has developed statistical methods for such purposes. "When this is done, the effects of sex and body mass appear negligible."

Read more at: 

Mobs are, sometimes, good

Date: November 8, 2016

Source: Michigan State University

Submitting to mob mentality is always a risky endeavor, for humans or hyenas. A new Michigan State University study focusing on the latter, though, shows that when it comes to battling for food, mobbing can be beneficial.

The findings, featured in the journal Current Zoology, fully describe for the first time, cooperative behavior during fights between two apex predators ¬- spotted hyenas and lions. Understanding the factors involved in the emergence of cooperation among organisms is central to the study of social evolution, said Kenna Lehmann, MSU doctoral candidate of integrative biology and study co-author.

"When hyenas mob during hyena-lion interactions, there is significant risk of injury by participating in this cooperative behavior," Lehmann said. "However, when they gang-up like this, they are more likely to win control of the food. This suggests that cooperative behavior increases fitness in hyenas."

Interestingly enough, hyenas will even mob lions when no food is present. The research team, part of University Distinguished Professor of integrative biology Kay Holekamp's lab, found that hyenas are more likely to mob lions when there are more hyenas present, regardless of food presence, fight location and how many lions are involved.

As this video shows, the interactions are intense. The mob sometimes starts small, but more hyenas enter the fray as the battle intensifies. Even against three lions, the smaller hyenas group as a single unit, giggling, growling and snapping like a hyena-headed hydra. Then, resembling a well-drilled military unit, they creep forward, drive the larger predators off a carcass and claim a feast for themselves and their clan.

Read on 

Facts About Hyenas

By Alina Bradford, Live Science Contributor | June 9, 2016 11:54pm ET

There are many misconceptions about hyenas. They aren't just scavengers. Not all of them laugh. They aren't wild dogs. They aren't even related to dogs. Here are some facts to clear up these misconceptions.

Size & description

Though many people compare hyenas to dogs, they are actually much more like cats. In fact, they are members of the suborder Feliformia, which is a classification for cat-like carnivores, according to Integrated Taxonomic Information System (ITIS). There are four species in the hyena family, and they vary in size. 

Spotted hyena

The spotted hyena is the largest species, and it grows to 4 to 5.9 feet (1.2 to 1.8 meters) long and 2.5 to 2.6 feet (77 to 81 centimeters) tall from paw to shoulder. They weigh 88 to 190 lbs. (40 to 86 kg). Unlike other species, spotted females are 10 percent heavier than males, according to the San Diego Zoo.

The spotted hyena's coat is sandy, yellowish or gray, according to the Animal Diversity Web (ADW). It has dark brown or black spots over most of the body.

Brown hyena

Brown hyenas are the second largest, ranging from 51 to 63 inches (130 to 160 cm) long and weighing 75 to 160 lbs. (34 to 72.6 kg), according to ADW. Brown hyenas can be distinguished from other hyenas by the long, shaggy hair, which is dark brown or black on the body and tan on the shoulders and neck. Hair on the neck grows to about 12 inches (30.5 cm), in contrast to the short hair on the legs, face and ears. The tail is short and bushy. The forelegs, which are horizontally striped, are much longer and more massively built than the hind legs, giving the brown hyena the appearance of always climbing a hill.

- See more at: 

Hyenas, jackals feast at vulture restaurants

24 September 2014 Last updated at 12:18

By Jonathan WebbScience reporter, BBC News

"Restaurants" of dead meat set up for endangered vultures also attract an undesirable clientele of hyenas and jackals, according to a six-year study.

The research consisted of repeated "scat surveys" (dung counts) at two nearby sites in South Africa.

There was a surge in numbers of both the cheeky mammals, specifically at the site with extra food, which went back down again when the restaurants closed.

The scientists have recommended a new strategy to help boost vulture numbers.

The birds have been in decline worldwide for a number of reasons.

Specifically, the researchers suggest using fences to exclude the unwanted, earthbound customers, and dishing up the extra meat for the vultures in random locations instead of re-stocking a regular carrion pantry.

Continued ...

African wild dogs adapt use of space to co-exist with lions and hyenas

(Phys.org) —African wild dogs share their habitat with other, larger carnivores such as lions and spotted hyenas. In a recent paper, published in PLOS one, it was found that African wild dogs adapt their use of space to avoid some larger carnivores. This allows wild dogs to co-exist with lions and hyenas, provided there is enough space to do so.

Carnivore competition

We mostly think of large carnivores being in competition with the prey they hunt and eat. But recently there has more recognition of the conflicts that occur between different carnivore species. African wild dogs, lions and spotted hyenas are just three of many carnivores that inhabit the Hluhluwe–iMfolozi National Park in South Africa. The park is set over about 96,000 hectares, about the size of a small county.

Read more at:

No Blue Skies for Mice: Scientist Study Differential Distribution of Photoreceptors in Retina of Mice

Dec. 4, 2013 — Guppies, hyenas and mice share one particular retinal specialization in their eye: Photoreceptors ("cones") sensitive to 'green' light are largely located in the top half of the eye, whereas cones sensitive to 'blue' light dominate the bottom half. Since the lens inverts the image as it enters the eye this arrangement seems to make intuitive sense: blue light from the sky is detected by the blue cones, while the greenish light from the ground falls onto the green cones.

Scientists led by Thomas Euler at the Werner Reichardt Centre for Integrative Neuroscience at the University of Tübingen have investigated this retinal specialization in mice. In their study, just published in the journal Neuron, they show that this arrangement is not an adaptation to the predominating 'colors' of the sky and the ground, as was previously thought. Their experiments showed that the apparent match between 'color' and differential cone distribution brings the animals no advantage. "The green cones would 'see' the light in the sky just like the blue cones," explains Thomas Euler. Instead, this specialized distribution of cones appears to subserve a much more fundamental aspect of vision: the detection of dark-light contrasts.

Read more

Captive Hyenas Outfox Wild Relatives

Jan. 7, 2013 — When it comes to solving puzzles, animals in captivity are, well, different animals than their wild brethren.

Testing animals' ability to solve new problems has been historically conducted on animals in captivity. Only recently has a shift been made to run these tests on animals in their natural habitat. In a study appearing in Animal Behaviour, however, researchers at Michigan State University found vast differences in the problem solving skills between captive and wild spotted hyenas.

Applying lessons learned from captive animals is potentially problematic because they may not accurately portray how wild animals respond to novel challenges, said Sarah Benson-Amram, former MSU zoology graduate student and the study's lead author.

"We have to be careful when interpreting results from captive animals, as there may be extreme differences between how animals behave in captivity and in the wild," said Benson-Amram, who is now a research fellow at the University of St. Andrews (Scotland). "An animal that is successful at solving problems in the comfort of its cage may be unwilling to engage in similar problem-solving behavior in the wild."

Continued:  http://www.sciencedaily.com/releases/2013/01/130107110523.htm

Large numbers of hyenas and humans coexist, study finds

Large hyena populations are living alongside human communities in Africa without coming into conflict, a recent study has found.

An international team of scientists surveyed the population size and diet of spotted hyenas in northern Ethiopia.

The study found a large hyena population with a diet that consisted almost exclusively of domestic animals.

Humans and hyenas are able to coexist because the cost of livestock predation to the local people is relatively low.

The results are published in the journal of Mammalian Biology.

Spotted hyenas (Crocuta crocuta) are common large carnivores of sub-Saharan Africa, and are the most important large scavengers and hunters in many areas of Ethiopia.

Continued:  http://www.bbc.co.uk/nature/20031460

Creative Hyenas Make Better Problem-Solvers

For humans, cracking a complicated puzzle often involves more than persistence — it requires thinking creatively and testing many possible solutions. A new study suggests the same holds true for hyenas.

Researchers from Michigan State University (MSU) studied wild spotted hyenas trying to open a steel puzzle box containing raw meat in Kenya. The box could be opened by sliding a bolt latch, but just nine out of 62 hyenas successfully opened it. The hyenas that solved the puzzle tested more potential solutions — including biting, flipping or pushing the box — than the ones that failed, the researchers said. However, sheer persistence didn't pay off.

"While those who gave up quickly were more likely to fail, some hyenas that spent more time with the puzzle box appeared to get stuck in a rut and would often try the same solutions over and over again," zoology graduate student Sarah Benson-Amram said in a statement from MSU.

Read on:  http://www.livescience.com/22207-creative-hyenas-make-better-problem-solvers.html

Hyenas Give Up Scavenging For Lent

Humans aren't the only ones who give up certain foods for Lent. In the 55 days before Easter in Ethiopia, hyenas are forced to turn from scavenging to hunting to make up for Christians' fasting traditions.

Members of the Orthodox Tewahedo Church give up meat and dairy during the Lent period in Ethiopia. Now, a new study of hyena droppings finds that local hyenas, deprived of butcher scraps during this time period, supplement their diets by hunting donkeys for food instead.

Spotted hyenas are adept hunters, capable of bringing down prey such as zebras, wildebeests and even young rhinoceroses. But these pack hunters are also adaptable: They scavenge freely, devouring everything from dead birds and mammals to garbage and dung.

"Hyenas can eat almost any organic matter, even putrid carrion and anthrax-infected carcasses," study researcher Gidey Yirga of Mekelle University in Ethiopia said in a statement. "They are capable of eating and digesting all parts of their prey except hair and hooves. Bones are digested so completely that only the inorganic components are excreted in the hyena's droppings."

Read on:  http://www.livescience.com/19490-hyenas-scavenging-lent.html