People don't always do as their neighbors do, and the same is true of neighboring chimpanzees.

German scientists say they've determined wild female chimpanzees copulate more frequently with males who share meat with them over long periods of time. Max Planck Institute for Evolutionary Anthropology researchers Cristina Gomes and Christophe Boesch said their findings strongly suggest that wild chimpanzees exchange meat for sex and do it on a long-term basis. Males who shared meat with females doubled their mating success, whereas females who had difficulty obtaining meat on their own increased their caloric intake without suffering the energetic costs and potential risk of injury related to hunting, said Gomes.

German researchers announced on Tuesday that female chimpanzees mate more often with males who give the meat.

In a population survey of West African chimpanzees living in Côte d'Ivoire, researchers estimate that this endangered subspecies has dropped in numbers by a whopping 90 percent since the last survey was conducted 18 years ago.

Conservationists say the dreaded Ebola virus along with decades of hunting and logging are putting some ape species on the brink of extinction in Central Africa.