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How could they? Poop-munching apes prompt quest for answers

Nov. 10, 2009
Special to World Science  

Na­ture can be beau­ti­ful. El­e­gant. Grace­ful.

But not al­ways. Be­lieve it or not, an­i­mals don’t do eve­ry­thing they do to im­press us. If you doubt it, look no fur­ther than the fact that some an­i­mals eat their own fe­ces. 

This phe­nom­e­non, called cop­roph­a­gy, oc­curs through­out the an­i­mal king­dom. It is par­tic­u­larly well-known among ro­dents, rab­bits and their rel­a­tives, and—less often—dogs and apes.

The par­ticipa­t­ion of this last group has caused caused par­tic­u­lar shock among hu­man wit­nesses, not least be­cause apes are sup­posed to be our close ev­o­lu­tion­ary rel­a­tives.

But two new stud­ies may of­fer a meas­ure of com­fort. At least, such as can be found in such a dis­mal situa­t­ion. 

The stud­ies sug­gest that chimps and bono­bos—the two spe­cies that are our clos­est ape rel­a­tives—eat po­o­p not for its own sa­ke, but in or­der to re­trieve hard, nu­tri­tious seeds from it.

Cop­roph­a­gy may be an “adap­tive feed­ing strat­e­gy dur­ing pe­ri­ods of food scarcity,” wrote Tet­suya Saka­maki of the Pri­ma­te Re­search In­sti­tute at Kyo­to Un­ivers­ity, Ja­pan, in a study pub­lished in the Oct. 31 ad­vance on­line is­sue of the jour­nal Pri­ma­tes.

Saka­maki re­ported that he spent a total of no less than 1,142 hours (48 days) watch­ing a group of about two doz­en wild bono­bos at the Lu­o Sci­en­tif­ic Re­serve in the Con­go. Among them, “at least five fe­males… prac­ticed cop­roph­a­gy and/or fe­cal in­spec­tion,” he wrote.

Samakaki found most of the episodes hard to see clear­ly, be­cause they oc­curred high in trees, but he came away with the im­pression that the apes were try­ing to get at seeds. In the most clearly vis­i­ble case, a young fe­male “used her lips to ex­tract Di­al­ium seeds from the fe­ces in her hand, ate the seeds, and dis­carded oth­er fi­brous parts in the fe­ces,” he wrote.

Di­alum plants are mem­bers of the leg­ume fam­i­ly.

A study in the April 2004 is­sue of the jour­nal sug­gested si­m­i­lar con­clu­sions re­gard­ing chim­panzees, not­ing that similar seed types were in­volved: “two types of Di­al­ium seeds were com­monly found in the fe­ces.”

The au­thors of this pre­vi­ous study added that stress, bore­dom or food scarcity did­n’t ap­pear to play a role in the cop­roph­a­gy. Saka­maki in the more re­cent study mostly agreed, except he wrote that cop­roph­a­gy did seem more com­mon when food was hard to find.

* * *

Nature can be beautiful, elegant, and graceful. But not always. Believe it or not, animals don’t do everything they do to impress us. If you doubt it, look no further than the fact that some animals eat their own feces. This phenomenon, called coprophagy, occurs throughout the animal kingdom, though particularly among rodents, rabbits and their relatives, and—less often—among dogs and apes. The participation of this last group has caused caused particular shock among human witnesses, not least because apes are supposed to be our close evolutionary relatives. But two new studies may offer a measure of comfort. At least, such as can be found in such a dismal situation. The studies suggest that chimps and bonobos—the two species that are our closest ape relatives—eat poop not for its own sake, but in order to retrieve hard, nutritious seeds from it. Coprophagy may be an “adaptive feeding strategy during periods of food scarcity,” wrote Tetsuya Sakamaki of the Primate Research Institute at Kyoto University, Japan, in a study published in the Oct. 31 advance online issue of the journal Primates. Sakamaki reported recently that he spent no less than 1,142 hours (48 full days) watching a group of about two dozen wild bonobos at the Luo Scientific Reserve in the Congo. Among them, “at least five females… practiced coprophagy and/or fecal inspection,” he wrote, reporting his findings in the Oct. 31 online issue of the research journal Primates. Samakaki found most of the episodes hard to see clearly, because they occurred high in trees, but he came away with the impression that the apes were trying to get at seeds. In the most clearly visible occurrence, a young female “used her lips to extract Dialium seeds from the feces in her hand, ate the seeds, and discarded other fibrous parts in the feces,” he wrote. Dialum are members of the legume family. A study in the April 2004 issue of the journal suggested similar conclusions regarding chimpanzees, noting that “two types of Dialium seeds were commonly found in the feces” after chimps ate the fruit. The authors of this previous study added that stress, boredom or food scarcity didn’t appear to play a role in the coprophagy, although Sakamaki in the more recent study demurred, suggesting that coprophagy was more common when food was hard to find.