Thursday, August 21, 2008

Happy Hyrax Rock

*Note: Text and all photos in all Kenya posts are by Shawn Billerman unless otherwise noted.

Around the middle of the trip, our adventures had slowed down, as we buckled down and worked mostly on our projects. However, on one particular afternoon, Irby took the group to Clifford’s Rock, a kopje where Rock Hyraxes lived. And, of course, where there are hyraxes, there is the very distinct chance of seeing a Verreaux’s Eagle (Aquila verreauxii), which feeds almost exclusively on the dumpy, furry creatures. En route to Clifford’s rock, we passed a covey of Vulturine Guineafowl (Acryllium vulturinum). These really are quite bizarre creatures, and definitely more exciting than Helmeted Guineafowl (Numida meleagris).

Vulturine Guineafowl (Acryllium vulturinum) (photo by Jess Marion)

We pulled up to the base of the outcrop, and began ascending. On the way up, we noted some of the fauna that is adapted to these rocky outcrops, like Klipspringer, which look a lot like a large Dik-dik on its tippy-toes. I also noticed a high abundance of Cinnamon-breasted Rock-buntings, and Marico Sunbirds. Also present were African Black-headed Oriole, and my first Red-faced Crombec. We did not see many hyrax at first, but certainly evidence of hyrax presence.

A perfect Hyrax skull found on the ground on the outcrop

For a while, we all just wandered around the top of the kopje, taking in the awesome scenery.

View from the top (or near top) of Clifford's Rock; the class climbing some lower rocks; Neat rock formations

But, our time of relaxation was short lived. Back to work! We all gathered, and we had two of our paper discussions on Clifford’s Rock. One of these discussions was appropriately on hyraxes, and we were under the watchful eye of a pair of Rock Hyraxes as we discussed their meta-population structure. As we were discussing hyrax populations, a Verreaux’s Eagle blitzed by, all the while Wire-tailed Swallows were foraging above our heads.

A pair of Rock Hyrax (Procavia johnstoni) watch as we discuss their metapopulation structure

As Nick pointed out to me in an earlier draft of this post, I talk about talking about Hyraxes, which is silly. So allow me to go into some detail about these bizarre, dirty mammals.

Hyraxes are in their own order, Hyracoidea, and the family Procaviidae. Hyraxes now fall into three genera, Dendrohyrax (tree-hyraxes), Heterohyrax (bush-hyraxe), and Procavia (rock-hyraxes). Hyraxes are part of the Afrotherian radiation, which include Elephants, Dugongs (Manatees), Elephant-shrews, Golden Moles, Tenrics, and the Aardvark. Hyraxes actually form a monophyletic clade with Elephants and Dugongs (Nishihara et al. 2005; Murata et al. 2003).

Now that I've covered the Hyraxes' bizarre evolutionary relationships, allow me, if you will, to go into some of their bizzarrre natural history. Hyraxes feed on graze and browse (Rock hyraxes graze, while Bush hyraxes browse), but do not chew cud. It is due to this inefficient way of extrating nutrients from vegetation that has forced them into marginal niches (source). In addition, hyraxes have poor thermoregulation, and are required to bask in the sun, and huddle for warmth (the necessity to bask leaves them very vulnerable to predators like Verreaux's Eagle). Hyraxes also utilize latrines, which may be hundreds of years old. Latrines may act as scenting areas where all members of a group collect the same scent on fur and feet (Kingdon 1997)

Unlike many mammalian social systems where males disperse and females remain in their natal territory, female Rock Hyrax disperse to neighboring kopjies. However, the number of females that actually disperse is quite small. This leads to lots of inbreeding, where males aquire large harems, often including sisters and daughters (source). (Gerlach and Hoeck 2001)

A final interesting aspect to Rock and Bush hyraxes is that they often live on the same kopjies. In fact, Rock and Bush Hyrax babies are raised in the same nurseries. Although it may seem strange that two different genera will raise each others young, to which there is clearly a cost, the cost of predation is far greater; by sharing duties raising offspring, they can keep better vigilence for predators (Barry and Mundy 2002).

For more pictures, and fun anecdotes about hyraxes, check out this website.


Barry, R.E. and P.J. Mundy. 2002. Seasonal variation in the degree of heterospecifc association of two synoptic hyraxes (Heterohyrax brucei and Procavia capensis) exhibiting synchronus parturition. Behavioral Ecology and Sociobiology. 52:3, pg. 177-181.

Gerlach, G. and H.N. Hoeck. 2001. Islands on the plains: metapopulation dynamics and female biased dispersal in hyraxes (Hyracoidea) in Serengeti National Park. Molecular Ecology. 10:9, pg. 2307-2317

Kingdon, J. 1997. The Kingdon Guide to African Mammals. 296-298. Academic Press, San Diego, CA.

Nishihara, H., Y. Satta, M. Nikaido, J.G.M. Thewissen, M.J. Stanhope, N. Okada. 2005. Molecular Biology and Evolution. 22(9):1823-1833

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