By KAY E. HOLEKAMP
Kay E. HoleKamp, a zoologist at Michigan State University, writes from the Masai Mara National Reserve in Kenya, where she is studying the behavior of spotted hyenas.
Tuesday, June 21
“When there are so many nicer animals out there, why study hyenas?”
That is the question my mother asked me when I first told her back in the mid-1980s that I was planning to move to Kenya to study spotted hyenas. Back then, before I actually started working with hyenas, I would have answered by saying, “Because I have an opportunity to go to Africa to study an interesting large mammal, and those kinds of opportunities are too rare to pass up. I’ve wanted to do something like this all my life, and now I have a chance to do it.”
Back in those days, I thought I would move to Kenya for a few years, conduct a dissertation-length project on spotted hyenas, then move on to a study yet another new animal in another new place. I had no idea then that I would just fall in love with these animals, or that they would hook me so completely with their complexity and their oddity. Nor did I have any idea back then how useful a model system these hyenas might offer for studying phenomena as wide-ranging as immune function, skull morphology, social networks, conservation biology and the evolution of intelligence.
If my mother asked that same question today, I’d answer it very differently.
Kay E. Holekamp
C. WilsonHyenas are capable of taking down much larger prey.
Anyone who enjoys brain-teaser crosswords or whodunit mystery novels will find spotted hyenas intriguing. They are to other mammals what chess is to board games or bridge is to card games. These animals present us with a series of challenging puzzles that beg to be solved. They intrigue us with their appearance, their behavior, their evolutionary origins, and their social lives. These animals look much like dogs yet they are far more closely related to cats than dogs, and their closest living relatives outside their own family are mongooses. Female spotted hyenas have evolved to look, and in many ways to behave, more like males than females. They are much more aggressive than males, and they are socially dominant to males, yet they are tender and devoted mothers who care for their cubs far longer and more intensively than do females in most other carnivore species. Spotted hyenas have the same hunched profile as their closest living relatives, striped and brown hyenas, which subsist mainly on carrion, and none of these animals look like they would be capable hunters. But spotted hyenas are powerful and effective hunters that can single-handedly bring down an antelope three times their own body mass. Spotted hyenas are large predators like lions or wolves, yet they live in elaborate societies much more like those of baboons than those of any other mammalian carnivore. Despite this, they often forgo the apparent benefits of group hunting, and instead hunt alone. They are often called “laughing hyenas,” yet their giggles indicate not that the caller is amused, but rather that it is frightened or being harassed. All these unusual traits have taught me that studying spotted hyenas requires an open mind and a willingness to recognize that, in the natural world, things are not always what they seem.
This year I am here in the Mara, along with a big crew of students, to address questions about a couple of the unusual traits expressed by spotted hyenas. First, I am helping my students study why females are larger than males in this species. We are collecting data needed to answer this question from the body measurements we take whenever we immobilize hyenas. We are also extracting DNA, both from blood collected during immobilizations and from hyena feces. One of my missions this summer is to collect genetic material from as many hyenas as possible so we can perform paternity analyses to answer questions about which males female hyenas choose to sire their cubs. Another reason for my visit to Kenya this year is to help two new grad students in my lab, Julia Greenberg and David Green, get the data collection for their respective dissertation projects up and running smoothly. David’s project, which is designed to enhance conservation of large mammalian carnivores in the Mara, is already moving forward nicely, but we are having some trouble selecting the best methods for Julia’s project.
Julia wants to find out whether the increasing pastoralist activity on the eastern side of the Mara is affecting the social and cognitive development of hyena cubs, and if so, whether these effects are being mediated by stress hormones. To do so, she needs to develop a host of methods nobody in my lab has used before; my main role here is merely to suggest materials and methods she might try. One of our first missions is to figure out how to measure stress hormones in individual hyena cubs. It is relatively easy to do this in older hyenas because we have previously developed methods for measuring stress hormones in feces. Now, whenever we see hyena feces, we rush over and collect it and freeze some for later hormone extraction. The problem for young cubs is that we rarely see them defecate by the den, and when they do, several cubs usually do it in the same spot at once, so it becomes impossible to tell which came from which cub. So Julia is attempting to collect saliva samples from individual cubs, because stress hormone concentrations vary in saliva like they do in blood or feces. This week, while parked by the den, we’ve tried getting individual cubs to slobber on a clean “kong” dog toy tied to our car. Although the cubs love the “kongs,” we’ve found that their saliva evaporates too quickly off the toy’s surface for us to collect enough for testing. Now we’re trying to get the cubs to chew on small absorbent cotton cylinders injected with powdered milk that are tied to the car or staked to the ground, but if readers have any ideas about what to try next, we’re all ears.