Eve Davidian, Bettina Wachter, Ilja Heckmann, Martin Dehnhard, Heribert Hofer, Oliver P. Höner
In most animal societies, resources are not shared equally among members of a group. Those at the top of the social hierarchy eat the tastiest food, get the comfiest sleeping spots, and can hang out – and more if they hit it off – with the most attractive and fertile mates. In the animal world, where lifetime achievement is largely determined by the number of offspring one leaves behind, it is rather straightforward why individuals should work hard to reach the top and remain there for as long as they can.
What we still don’t quite understand is how social rank influences reproductive success. Do high-ranking males father more offspring and offspring of higher quality than low-ranking males because they are stronger and more attractive? Or is it because they are less “stressed” by competition with other males and can afford to invest more in courting females?
To answer these questions, we did fieldwork in the African savannah. Lots of fieldwork. Over 20 years of searching, identifying, assessing paternities, and monitoring the behaviour of thousands of free-ranging spotted hyenas in the Ngorongoro Crater in Northern Tanzania. We also collected over 400 steaming hyena turds to measure the concentration of cortisol, an estimate of the physiological costs – or so-called “stress” – borne by a hyena.
We found that interactions with other males are more stressful for low-ranking males than for their high-ranking counterparts and that this restricts the time and energy they can invest in courting the most fertile – and most contested – females. We also found that males have to juggle romance and more mundane duties like getting acquainted with new clan mates and maintaining old friendships and alliances. But low-ranking males shy away from these stressful activities and prefer to spend more time on their own, munching on bones or chilling in stinky puddles.
But don’t feel too sorry for these low-ranking males. Their time will come. The social rank of male spotted hyenas is determined by a queuing convention. Most males eventually climb the social ladder and get to enjoy the perks of being the top dog.
To find out more about spotted hyenas and our research team, visit the Hyena Project – Ngorongoro Crater website
To learn what it takes to be a hyena poop hunter, check out our blogpost for the journal Methods in Ecology and Evolution