Eat That Coal Monkey!

I’ve been getting the periodical Natural History for several years now. I originally read it for Stephen Jay Gould’s monthly essays on paleontology, evolution, and sometimes even baseball (always with a poignant lesson on the history of science or to point out some fallacy of understanding in evolutionary theory). Since the great master’s death, however, the magazine has gone into some decline. There are only a few featured articles now, and it’s evolved to be a fairly slim fifty page periodical.

And yet one thing that continually impresses me is the photography. The magazine cover has always been an attention-getter with a vivid photo of some exotic animal (often with awesome pigmentation or other interesting morphology). The Dec/Jan 2010-2011 issue has a picture of the Zanzibar red colobus monkey (Procolobus kirkii). Its expression is just amazing in a Zen-like way: perfectly at home in its surroundings, perfectly composed.

Natural History also features a centerfold photo in which this issue has a snap of a male P. kirkii that is eating coal. What the hell is he up to? A short article on the primate by naturalist Fred Bruemmer accompanies the photos.

Zanzibar Red Colobus Monkey (Procolobus kirkii)
Photo courtesy of Olivier Lejade

How the monkeys initiated the habit is unknown. The behavior is transmitted maternally by imitation, and is confined to a small population in the Jozani Forest on Unguja, the main island of Zanzibar, according to primatologist Thomas T. Struhsaker of Duke University. The monkeys have taken up the practice since the Indian mango and almond have been introduced. The leaves are rich in phenolic compounds that, when eaten in large quantities, are toxic. Coal binds many toxic compounds and not nutritious proteins in the monkey’s digestive tract. They steal coal from man-made hearths or from burnt-out tree trunks. There are only 2,000 Zanzibar reds left on Unguja, down from a population of 375,000 in 1988.