The U.S. Fish and Wildlife Service on Tuesday proposed declaring all chimpanzees endangered, which would reverse a 1990 decision to classify wild chimps as endangered but captive chimps as merely threatened. The split classification facilitated medical research, and a new designation could make it more difficult to perform experiments on chimps. How many captive chimpanzees would be capable of surviving in the wild?
Not many. Chimpanzee reintroduction programs focus almost exclusively on wild-born orphans who lost their mothers to poachers, rather than captive-born chimps. That decision has little to do with physical prowess: Chimpanzees born and raised in reputable zoos and sanctuaries don’t differ much physically from wild chimps. Given adequate space and environmental enrichment, they cover nearly as much ground and burn approximately as many calories as they would in the wild. (It’s difficult to precisely measure the strength of a chimpanzee, though.) The zoo diet, while less varied than the wild diet of 102 plant species and occasional meats, has the benefit of consistency and can enhance a chimp’s growth. In addition, basic foraging skills seem to be either instinctive or easily learned in captivity. When zookeepers fill artificial termite mounds with ketchup, for example, captive chimps use the old twig trick to extract the food without any instruction.
Despite these impressive attributes, it would be very risky to release even the most robust captive-born specimens into the wild. Primatologists worry, first and foremost, that chimps in non-African zoos could introduce novel diseases into wild populations. Another significant problem is room. Habitat loss accounts for much of the decline in wild chimpanzee populations. Adding captive-born individuals into the mix would probably lead to warfare over limited resources.
Socialization is another major obstacle. Chimps live in multiple-male societies, featuring ever-shifting alliances and struggles over food and sex. Captive chimpanzees usually live in simpler communities, sometimes with only one or two adult males, and they don’t learn how to navigate the cloak-and-dagger intrigue of a wild troop.
Reintroduction experiments demonstrate how captive living stunts the social development of even wild-born chimpanzees. Between 1996 and 2001, Aliette Jamart released 37 orphaned chimps into a monitored wild space in the Republic of Congo. Although they received extensive preparation for life in the wild, 18 of the newbies suffered attacks from wild chimpanzees. The victims fared poorly in combat. Five of them died and nine disappeared. The assailants bit and clawed at the anogenital regions of the introduced chimpanzees, suggesting the attacks had something to do with sexual and territorial dominance. Introduced males were targeted more than females. Today, reintroduction programs prioritize females.
Chimpanzees raised as minstrels for human entertainment, medical research, or in unaccredited facilities constitute an entirely separate category. There are more than 1,000 such individuals in the United States today. Many of them are physical weaklings, raised in solitude by doting humans or compromised during experimentation. Not only would they be terrible candidates for reintroduction, their very existence seems to threaten the wild population. A pair of studies released in 2011 showed that seeing chimpanzees with humans, often in television commercials, makes people less likely to believe that wild chimpanzees are endangered.
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Explainer thanks Steve Ross of the Lincoln Park Zoo and ChimpCare.