SCIENCE DECEMBER 12, 2013
Last week, the Nonhuman Rights Project filed three lawsuits seeking "legal personhood" for four chimps who live upstate and are used for research—or, as the NRP puts it, are “imprisoned”— but this week New York judges denied the animal-rights group’s claims. Just how much do chimps have in common with people, though? Consider the following studies:
Chimps empathize with their friends
Yawning when you see another person yawn is a sign of empathy. Humans do it, more often in response to family members or friends than strangers, and primatologist Frans de Waal has shown that the same is true for chimps: "Twenty-three chimpanzees (Pan troglodytes) from two separate groups watched videos of familiar and unfamiliar individuals yawning or at rest (control). The chimpanzees yawned more when watching the familiar yawns than the familiar control group or the unfamiliar yawns, demonstrating an in-group-out-group bias in contagious yawning."
They get stressed out about moving
Human psychologists have made “relocation stress syndrome” an official diagnosis—but it may be applicable to chimps, too. When 72 chimps were relocated from an animal research center in Arizona to one in Texas, researchers looked for chemical signs of stress before, during, and after their journey. They found: “numerous statistically significant differences in hematological, clinical chemistry, and immunological parameters. Some of these were indicative of stress, and thus, changes in welfare state, although many remained within the published normal ranges for chimpanzees.” When the chimps were tested again three to 12 weeks after their arrival in Texas, most still hadn’t made a full recovery.
They learn from each other
Social learning is often thought of as a uniquely human process, but Swiss primatologist Christophe Boesch has produced compelling evidence that chimps teach each other behaviors like cracking nuts through a complex, intergenerational social process. Boesch, who spent years observing chimps in Cote d’Ivoire, identified three key phases young chimpanzees go through as they learn to crack nuts. First, young chimps make unsuccessful attempts to crack nuts open without the proper tools, like simple hammers and anvils. In the second phase, which sets in at around age three, chimps begin to understand the relationships between nuts, hammers and anvils, but they lack the necessary physical strength. Only in the final stage, when the development of their musculature coincides with sufficient cognitive awareness, do they manage to regularly crack open nuts. When researchers gave nuts, hammers and anvils to captive chimpanzees that had grown up in zoos, they found that they were far less adept at cracking the nuts—leading researchers to conclude that chimps must learn from adults and others of their own kind.
They can recognize each other by their butts
We’ve known since 1970 that chimps can be taught to recognize their own reflections in a mirror, and last year De Waal and Jennifer Pokorny showed that chimps can also recognize members of their social groups—from photos of just their behinds. Researchers presented adult chimps with photos of other chimps’ behinds, and were easily able to train them to select the facial image that corresponded with the behind—a sure sign of interpersonal awareness and intelligence.
Not all chimps have the same grooming and courtship habits
Scottish researcher Andrew Whiten studied seven African chimp populations and identified 65 categories of behavior, 42 of which differed from site to site—to such an extent that he believed different chimp “cultures” could be identified.
Each community exhibits an entire set of behaviors that differentiates it from other groups. As a result, we can talk about “Gombe culture” or “Tai culture.” Indeed, once we observe how a chimpanzee behaves, we can identify where the animal lives. For instance, an individual that cracks nuts, leaf-clips during drumming displays, fishes for ants with one hand using short sticks, and knuckle knocks to attract females clearly comes from the Tai Forest. A chimp that leaf grooms and hand-clasps during grooming can come from the Kibale Forest or the Mahale Mountains, but if you notice that he also ant-fishes, there is no doubt anymore—he comes from Mahale.
Not all chimps have the same table manners
In one of the most famous studies of chimpanzee behavior, anthropologist Jane Goodall observed that chimps in Gombe National Park in Tanzania would use twigs or blades of grass as tools to “fish” termites out of trees: When the chimps poked their tools into the termites’ habitat, they would react by defensively biting the tool—at which point the chimp only had to extract the tool to enjoy a termite feast. In the Gombe, chimps tend to use both ends of a twig before throwing it away, but on Mount Assirik in Senegal, they discard the twig after using only one end. This cannot, according to researchers, be explained by ecological differences—so we turn to cultural ones.
Chimps are complex creatures, and the Nonhuman Rights Project doesn’t plan to give up. But bad things happen when we forget that chimps are not humans.