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‘Friendly’ hyenas are more likely to form mobs



‘Friendly’ hyenas are more likely to form mobs

After more than 35 years of surveillance, Michigan State University researchers are exposing some of the secret workings of mobs.

To be clear, these mobs are made up of spotted hyenas.

Publishing in the journal Proceedings of the Royal Society B, the MSU team revealed that relationships and social interactions between hyenas can influence when two or more animals decide to work together to attack lions. This type of cooperative behavior is called mobbing.

“Social relationships can overcome barriers to mobbing and let hyenas achieve cooperation,” said Tracy Montgomery, a lead author of the new report.

Montgomery started the project while earning her doctorate in the lab of Kay Holekamp at MSU and was supported by the Dr. Marvin Hensley Endowed Scholarship Fund in Zoology.

“If hyenas greet each other, they’re more likely to mob,” said Montgomery, who is now a postdoctoral researcher at the Max Planck Institute of Animal Behavior and the University of Konstanz in Germany. “If they have strong social bonds, they’re more likely to mob.”

Spotted hyenas are social creatures with complex social structures that are similar to baboons and other primates. Researchers study animals like these to explore how cooperative behaviors — like teaming up against a common foe — have evolved not just in wildlife, but in humans as well.

“It’s fascinating because this seems like something humans would do,” said Kenna Lehmann, another lead author who also worked on the project while earning her doctorate as part of Holekamp’s team. She’s now an assistant professor at MSU.

“The relationships they build over time make a difference,” Lehmann said. “It’s not just, ‘I’ll give you a zebra leg if you help.'”

“One of the coolest things about this paper is the finding that hyenas are sensitive to social relationships across a range of temporal scales,” added Holekamp, a University Distinguished Professor of integrative biology in MSU’s College of Natural Science.

“They base their decisions about whether or not to cooperate in mobbing lions on both immediate-term friendly behaviors and long-term, friendship-like relationships.”

‘So weird and fascinating’

Holekamp has been studying hyenas in Kenya for 35 years, but that wasn’t her original plan.

“I went to Kenya in 1988 thinking I’d do a dissertation-length project — three or four years — with hyenas, then I’d move on to study dolphins or monkeys or some other animals,” said Holekamp, who is also a core faculty member in MSU’s Ecology, Evolution and Behavior, or EEB, program.

“But the hyenas proved to be so weird and fascinating that they have kept my rapt attention.”

Take, as a weird and fascinating example, the fact that female spotted hyenas have what are known as pseudo-penises. Understanding why female genitalia is so similar to male genitalia is one of the big, looming biological questions about hyenas, Holekamp said.

Although that question doesn’t factor directly into this study, it does underscore why Holekamp finds hyenas so interesting.

“Spotted hyenas appear to violate many of the basic rules of mammalian biology,” Holekamp said. “By studying them, we can potentially determine what the rules really are.”

As doctoral students working with Holekamp, both Montgomery and Lehmann became interested in what hyenas’ rules of engagement were when it comes to mobbing lions.

“We wanted to understand why they would risk themselves in this way — because it is risky — and what they got out of it,” Montgomery said.

When researchers are able to determine what caused the death of a hyena, it’s a lion more than 25% of the time.

Lions and hyenas have overlapping territories, though. So, Lehmann and Montgomery first examined mobbing through the lens of its obvious benefits, such as fighting off lions for food.

In a 2017 report published in Current Zoology, the team showed that, although mobbing occurred most frequently near freshly killed food, hyenas also formed mobs when there was no obvious benefit.

“There were times we’d be watching them thinking, ‘Why are you doing that? That is such a bad idea,'” Lehmann said.

30 years in the making

In their new study, the researchers dug deeper into mobbing behavior to look at other motivations. In doing so, they also discovered that mobbing was more frequent when the risk of injury or death to hyenas was lower, even in the absence of a benefit.

For example, male lions are larger than females and more dangerous to hyenas. Hyenas were more likely to mob when there weren’t any male lions around. Conversely, in spotted hyenas, females are larger than males and females were more likely to join mobs.

But it was the social components of mobbing that stood out most to researchers, and it’s a discovery made possible by observing several generations of hyenas in the same habitat over 35 years. During that time, the team always had several collaborators present at its research camp in the Maasai Mara National Reserve.

“There’s no way we would have been able to do this study without it being part of a 35-year project,” Lehmann said.

One of the big reasons is that researchers don’t see mobs every day — far from it. The team observed about 1,000 mobbing interactions between hyenas and lions over the past three decades.

Rarer still are the interactions where researchers could record all the information they needed.

“These interactions are extremely fast paced, there are often many hyenas and lions present and most are moving around fairly quickly,” Holekamp said. “This makes accurately recording what happens in adequate detail to include in our analyses very challenging.”

Of those roughly 1,000 interactions, 325 had robust enough data for Montgomery and Lehmann to analyze and make their discoveries. The two credited the hard work of students, research assistants and other collaborators over the past 30 years, who helped standardize and organize observations from the field into usable data sets.

And Holekamp’s team is still working to find what other secrets those data sets hold.

“Finding these results was really exciting, but I feel like the fun part of science is you answer a question and you immediately have 50 more,” Montgomery said. “There are so many more things that we need to do with this data.”

This project was supported by the National Science Foundation, the National Institutes of Health and by the Human Frontier Science Program. You can learn more about the Mara Hyena project on the team’s blog and help support their next 30 years of research by donating.

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New snake discovery rewrites history, points to North America’s role in snake evolution




‘Friendly’ hyenas are more likely to form mobs

A new species of fossil snake unearthed in Wyoming is rewriting our understanding of snake evolution. The discovery, based on four remarkably well-preserved specimens found curled together in a burrow, reveals a new species named Hibernophis breithaupti. This snake lived in North America 34 million years ago and sheds light on the origin and diversification of boas and pythons.

Hibernophis breithaupti has unique anatomical features, in part because the specimens are articulated — meaning they were found all in one piece with the bones still arranged in the proper order — which is unusual for fossil snakes. Researchers believe it may be an early member of Booidea, a group that includes modern boas and pythons. Modern boas are widespread in the Americas, but their early evolution is not well understood.These new and very complete fossils add important new information, in particular, on the evolution of small, burrowing boas known as rubber boas.

Traditionally, there has been much debate on the evolution of small burrowing boas. Hibernophis breithaupti shows that northern and more central parts of North America might have been a key hub for their development. The discovery of these snakes curled together also hints at the oldest potential evidence for a behavior familiar to us today — hibernation in groups.

“Modern garter snakes are famous for gathering by the thousands to hibernate together in dens and burrows,” says Michael Caldwell, a U of A paleontologist who co-led the research along with his former graduate student Jasmine Croghan, and collaborators from Australia and Brazil. “They do this to conserve heat through the effect created by the ball of hibernating animals. It’s fascinating to see possible evidence of such social behavior or hibernation dating back 34 million years.”

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Good timing: Study unravels how our brains track time




‘Friendly’ hyenas are more likely to form mobs

Ever hear the old adage that time flies when you’re having fun? A new study by a team of UNLV researchers suggests that there’s a lot of truth to the trope.

Many people think of their brains as being intrinsically synced to the human-made clocks on their electronic devices, counting time in very specific, minute-by-minute increments. But the study, published this month in the latest issue of the peer-reviewed Cell Press journal Current Biology, showed that our brains don’t work that way.

By analyzing changes in brain activity patterns, the research team found that we perceive the passage of time based on the number of experiences we have — not some kind of internal clock. What’s more, increasing speed or output during an activity appears to affect how our brains perceive time.

“We tell time in our own experience by things we do, things that happen to us,” said James Hyman, a UNLV associate professor of psychology and the study’s senior author. “When we’re still and we’re bored, time goes very slowly because we’re not doing anything or nothing is happening. On the contrary, when a lot of events happen, each one of those activities is advancing our brains forward. And if this is how our brains objectively tell time, then the more that we do and the more that happens to us, the faster time goes.”

Methodology and Findings

The findings are based on analysis of activity in the anterior cingulate cortex (ACC), a portion of the brain important for monitoring activity and tracking experiences. To do this, rodents were tasked with using their noses to respond to a prompt 200 times.

Scientists already knew that brain patterns are similar, but slightly different, each time you do a repetitive motion, so they set out to answer: Is it possible to detect whether these slight differences in brain pattern changes correspond with doing the first versus 200th motion in series? And does the amount of time it takes to complete a series of motions impact brain wave activity?

By comparing pattern changes throughout the course of the task, researchers observed that there are indeed detectable changes in brain activity that occur as one moves from the beginning to middle to end of carrying out a task. And regardless of how slowly or quickly the animals moved, the brain patterns followed the same path. The patterns were consistent when researchers applied a machine learning-based mathematical model to predict the flow of brain activity, bolstering evidence that it’s experiences — not time, or a prescribed number of minutes, as you would measure it on a clock — that produce changes in our neurons’ activity patterns.

Hyman drove home the crux of the findings by sharing an anecdote of two factory workers tasked with making 100 widgets during their shift, with one worker completing the task in 30 minutes and the other in 90 minutes.

“The length of time it took to complete the task didn’t impact the brain patterns. The brain is not a clock; it acts like a counter,” Hyman explained. “Our brains register a vibe, a feeling about time. …And what that means for our workers making widgets is that you can tell the difference between making widget No. 85 and widget No. 60, but not necessarily between No. 85 and No. 88.”

But exactly “how” does the brain count? Researchers discovered that as the brain progresses through a task involving a series of motions, various small groups of firing cells begin to collaborate — essentially passing off the task to a different group of neurons every few repetitions, similar to runners passing the baton in a relay race.

“So, the cells are working together and over time randomly align to get the job done: one cell will take a few tasks and then another takes a few tasks,” Hyman said. “The cells are tracking motions and, thus, chunks of activities and time over the course of the task.”

And the study’s findings about our brains’ perception of time applies to activities-based actions other than physical motions too.

“This is the part of the brain we use for tracking something like a conversation through dinner,” Hyman said. “Think of the flow of conversation and you can recall things earlier and later in the dinner. But to pick apart one sentence from the next in your memory, it’s impossible. But you know you talked about one topic at the start, another topic during dessert, and another at the end.”

By observing the rodents who worked quickly, scientists also concluded that keeping up a good pace helps influence time perception: “The more we do, the faster time moves. They say that time flies when you’re having fun. As opposed to having fun, maybe it should be ‘time flies when you’re doing a lot’.”


While there’s already a wealth of information on brain processes over very short time scales of less than a second, Hyman said that the UNLV study is groundbreaking in its examination of brain patterns and perception of time over a span of just a few minutes to hours — “which is how we live much of our life: one hour at a time. ”

“This is among the first studies looking at behavioral time scales in this particular part of the brain called the ACC, which we know is so important for our behavior and our emotions,” Hyman said.

The ACC is implicated in most psychiatric and neurodegenerative disorders, and is a concentration area for mood disorders, PTSD, addiction, and anxiety. ACC function is also central to various dementias including Alzheimer’s disease, which is characterized by distortions in time. The ACC has long been linked to helping humans with sequencing events or tasks such as following recipes, and the research team speculates that their findings about time perception might fall within this realm.

While the findings are a breakthrough, more research is needed. Still, Hyman said, the preliminary findings posit some potentially helpful tidbits about time perception and its likely connection to memory processes for everyday citizens’ daily lives. For example, researchers speculate that it could lend insights for navigating things like school assignments or even breakups.

“If we want to remember something, we may want to slow down by studying in short bouts and take time before engaging in the next activity. Give yourself quiet times to not move,” Hyman said. “Conversely, if you want to move on from something quickly, get involved in an activity right away.”

Hyman said there’s also a huge relationship between the ACC, emotion, and cognition. Thinking of the brain as a physical entity that one can take ownership over might help us control our subjective experiences.

“When things move faster, we tend to think it’s more fun — or sometimes overwhelming. But we don’t need to think of it as being a purely psychological experience, as fun or overwhelming; rather, if you view it as a physical process, it can be helpful,” he said. “If it’s overwhelming, slow down or if you’re bored, add activities. People already do this, but it’s empowering to know it’s a way to work your own mental health, since our brains are working like this already.”

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Another intermediate-mass black hole discovered at the center of our galaxy




‘Friendly’ hyenas are more likely to form mobs

While researching a cluster of stars in the immediate vicinity of the supermassive black hole SgrA* (Sagittarius A*) at the centre of our galaxy, an international team of researchers led by PD Dr Florian Peißker has found signs of another, intermediate-mass black hole. Despite enormous research efforts, only about ten of these intermediate-mass black holes have been found in our entire universe so far. Scientists believe that they formed shortly after the Big Bang. By merging, they act as ‘seeds’ for supermassive black holes. The study ‘The Evaporating Massive Embedded Stellar Cluster IRS 13 Close to Sgr A*. II. Kinematic structure’ was published in The Astrophysical Journal.

The analysed star cluster IRS 13 is located 0.1 light years from the centre of our galaxy. This is very close in astronomical terms, but would still require travelling from one end of our solar system to the other twenty times to cover the distance. The researchers noticed that the stars in IRS 13 move in an unexpectedly orderly pattern. They had actually expected the stars to be arranged randomly. Two conclusions can be drawn from this regular pattern: On the one hand, IRS 13 appears to interact with SgrA*, which leads to the orderly motion of the stars. On the other hand, there must be something inside the cluster for it to be able to maintain its observed compact shape.

Multi-wavelength observations with the Very Large Telescope as well as the ALMA and Chandra telescopes now suggest that the reason for the compact shape of IRS 13 could be an intermediate-mass black hole located at the centre of the star cluster. This would be supported by the fact that the researchers were able to observe characteristic X-rays and ionized gas rotating at a speed of several 100 km/s in a ring around the suspected location of the intermediate-mass black hole.

Another indication of the presence of an intermediate-mass black hole is the unusually high density of the star cluster, which is higher than that of any other known density of a star cluster in our Milky Way. “IRS 13 appears to be an essential building block for the growth of our central black hole SgrA*,” said Florian Peißker, first author of the study. “This fascinating star cluster has continued to surprise the scientific community ever since it was discovered around twenty years ago. At first it was thought to be an unusually heavy star. With the high-resolution data, however, we can now confirm the building-block composition with an intermediate-mass black hole at the centre.” Planned observations with the James Webb Space Telescope and the Extremely Large Telescope, which is currently under construction, will provide further insights into the processes within the star cluster.

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