Are monkeys carnivores herbivores or omnivores

Chimpanzees: Eating meat is a man's business

Whether steak, burger or sausage - men often find it more difficult than women to go without meat. But why? A British-German research team may have found the first clues. Because even with a group of wild chimpanzees in the jungle of the Ivory Coast, the men are the carnivores, the females mostly stick to a vegetable diet, as the researchers report in the journal "Proceedings of the National Academy of Sciences". Gender-specific differences in diet are therefore not a human invention.

For a long time, chimpanzees were considered pure herbivores. Because when observing outdoors, you usually saw them gathering nuts, fruits or leaves and chewing them. At the beginning of the 1960s, however, the picture changed: the chimpanzee researcher Jane Goodall discovered that the great apes also hunt and then even kill and eat other monkeys. It is now known that most chimpanzees eat meat now and then, albeit to different extents depending on their habitat and population.

Monkeys as prey for monkeys

"The range extends from groups that rarely hunt small animals and usually only when the opportunity arises to those who regularly and systematically hunt and then also kill medium-sized prey," explains Geraldine Fahy from Max -Planck Institute for Evolutionary Anthropology in Leipzig and her colleagues. The chimpanzees in Tai National Park in Ivory Coast are among the most specialized hunters among the great apes. They hunt and eat Colobus monkeys very often, as observations show. Usually males band together, hunt together and then split the meat.

Up to now, however, it was unclear exactly what proportion meat has in their diet and also how much meat consumption differs between the male and female group members. "It is difficult to monitor hunting in the wild, and even if you watch the monkeys doing it, this does not provide an overview of the proportion that meat has in their diet over the long term," say the researchers.

Hair and bones reveal meat consumption

Fahy and her colleagues therefore used an indirect method for their study: They collected hair from the chimpanzees in the Tai National Park and used preserved bones and hair samples from a total of 20 years of research. They analyzed these samples for the content of certain nitrogen and carbon isotopes. Because these are built into the body's own material from the food ingested and thus form a kind of archive of past meals.

For example, the carbon isotopes can be used to find out whether an animal has mainly eaten grass or fruit and leaves. The nitrogen, in turn, reveals the level of the food chain at which the feed was - whether it was a plant or an animal. Similar to humans, a chimpanzee hair grows around one centimeter per month, as the researchers explain. For their analyzes, they used six centimeters long hair and were able to draw conclusions about the diet for the past six months. The isotopes stored in bones go back even further.

Females hardly get any of the prey

Both the long-term and the short-term isotope values ​​showed that the adult males of the Tai chimpanzees eat significantly more meat than females or young animals, as Fahy and her colleagues report. This suggests that the hunted prey is primarily distributed among the fellow hunters. It is not the social rank that decides who gets more or less, but the hunting skills: good hunters were rewarded with more meat. The females are less lucky: Although they are almost always present when the males share their prey, they hardly get any of the meat. Only a select few apparently manage to get hold of a piece every now and then - in exchange for sex.

According to the researchers, this suggests that gender dietary differences may have existed in our distant ancestors as well. Neither eating meat nor the typically male preference for it is therefore a human invention. However: "This differentiates this chimpanzee population from most human hunter-gatherer communities in which the females receive a large proportion of the prey," the scientists state. It is now interesting to find out whether there are also pronounced differences in meat consumption among other chimpanzee populations. (Proceedings of the National Academy of Sciences (PNAS), 2013; doi: 10.1073 / pnas.1221991110)

(PNAS, March 26, 2013 - NPO)

March 26, 2013