Gibbons: The Forgotten Ape

31 July 2008

At some point in the next four months, Spain will likely become the first country to extend legal rights to great apes, thereby protecting gorillas, orangutans, chimpanzees, and bonobos from abuse, torture, and unnatural death. The measure will, in practical terms, prevent the inhumane confinement of and testing on great apes, which are singled out among nonhuman animals for their cognitive abilities-on par, it is believed, with a 1-year-old human child. But there's another ape that might be just as sensitive and intelligent as the great apes, and yet the Spaniards are prepared to offer it no special rights or protections. No one stands up for the gibbon.

There are five types of ape. Four are considered "great." The fifth is the gibbon. Greatness in apes is largely a matter of size, and the gibbon, maxing out at 30 pounds, doesn't make the cut. To primatologists, it is known instead as the "lesser ape"-or, as its partisans prefer, the "small ape." As a result, it's overlooked in everything from environmental protections to fantasies of simian domination. (There are no slave-driving gibbons in Planet of the Apes.) Humans have resolved to protect our evolutionary family, yet we continue to ignore one of our closest cousins.

Gibbons may be small, but they bear all the requisites of apehood: large brains, no tail, and rotary shoulder blades. Like orangutans, they populate Southeast Asia. They're typically black with white markings around their faces, as if dressed in furry habits. Swinging through the treetops at speeds up to 35 miles per hour, they look a bit like flying nuns.

The gibbon's arboreal lifestyle is unique among the apes and, along with its small size, often leads people to mistake it for a monkey. (An ape, of course, is not a monkey: Both are primates, but they're not in the same superfamily.) Peter Gabriel, for example: His music video for "Shock the Monkey" stars a gibbon. The creators of the popular YouTube video "Monkey Death Wish" similarly misattribute their leading role. And a child swinging from monkey bars emulates the brachiation of a gibbon more than the movement of any monkey. They should be called gibbon bars.

The laboratory turns out to be no better than the playground. "I think quite often some researchers just look at gibbons like monkeys," says Alan Mootnick, who runs the Gibbon Conservation Center in California. That's one reason so little is known about them, even though they're more common and diverse than any other ape, with four genera and at least a dozen species. (Seventy percent of all apes are gibbons.) Louis Leakey, the famous paleoanthropologist, encouraged Jane Goodall, Dian Fossey, and Birute Mary Galdikas to study chimpanzees, gorillas, and orangutans, respectively, but never dispatched an emissary to the gibbons. The practical difficulties faced by primatologists in the field also contribute to our ignorance: Gibbons live in small families in remote tropical canopies, while great apes like the chimpanzees and gorillas stay in large, terrestrial groups.

The scarcity of scientific knowledge about gibbons hampers advocacy on their behalf. In 1993, Princeton bioethicist Peter Singer co-founded the Great Ape Project, a nonprofit animal-rights organization based in Seattle. Singer's group champions the principle enshrined in the new Spanish law-extension of human rights to great apes on account of their self-awareness, sense of the future, and ability to use human language. Does the Great Ape Project leave out gibbons because they don't possess these special abilities? No. According to Singer, it's because "we just didn't know enough about them."

Scientists haven't proven gibbons deficient so much as they haven't bothered looking. The few who have relate encouraging results: Thomas Geissmann, director of the Gibbon Research Lab in Zurich, has observed mirror self-recognition in gibbons, which is generally regarded as a sign of self-awareness; others have observed tool use by gibbons in captivity. Alan Mootnick says he's met a gibbon capable of rudimentary sign language and suggests that gibbons may have more difficulty signing than the great apes because of the unique morphology of their hands-which are equal in length to human hands but half the width. However, all of these observations are anecdotal; high-level cognition in gibbons has not been systematically studied.

Meanwhile, there are whole institutes devoted to the study of the cognitive abilities of great apes. And many of their vaunted discoveries have come only after long and arduous work. For example, gorillas are often celebrated for their ability to recognize themselves in a mirror, but the earliest studies found just the opposite. Scientists began testing for self-recognition in gorillas in 1981 but did not find it until 10 years later. Koko, a research animal in California (and an alleged nipple fetishist), was able to identify her reflection. But she was a very special case: Humans had reared her since the age of 1. Some researchers are skeptical of mirror self-recognition in gorillas, but they have no problem rationalizing its absence, suggesting that the gorillas' aversion to eye contact might prevent them from looking in the mirror long enough. Gibbons have not had the benefit of such attention and large sample sizes. "In the initial studies, they just tested one or two gibbons and said, 'Oh yeah, they failed,' " says Geissmann.

Tests of animal self-recognition sometimes seem more like exercises in human self-recognition: Gorillas appear humanlike, so we test them repeatedly until we can prove they have some form of consciousness. Gibbons, on the other hand, look like monkeys, so we're inclined to dismiss them as "lesser" without a second thought. While it's true that the great apes are more closely related to each other than they are to gibbons, it's also true that the gibbons are more closely related to the great apes, including humans, than they are to any monkey.

As a result, interesting aspects of gibbon ethology have long been ignored. The lesser apes, for example, are the only apes besides humans to live in monogamous couples. Among the apes, their songs are second in acoustic sophistication only to humans', and they walk bipedally when grounded, unlike the great (nonhuman) apes. But it's hard to generate interest in the lesser apes, especially given that no charismatic human researcher-à la Goodall or Fossey-has ever taken up their cause.

What makes this particularly frustrating is that the most endangered species of ape isn't a gorilla, chimpanzee, or orangutan. Certain types of gibbon are in far greater trouble. The orangutan may be the beneficiary of a high-profile conservation campaign in Indonesia, but it's not as rare as the Javan gibbon. In four decades, the western hoolock gibbon has declined in number from 100,000 to just 5,000. The Hainan gibbon, of which only 20 or so individuals survive, is perhaps the most endangered primate in the world. The eastern black-gibbon population in Vietnam has similarly dwindled to a few dozen.

Such species are unlikely to survive as long as humans treat gibbons as second-rate apes. Recently, there have been some encouraging signs: Legislation introduced in the U.S. House of Representatives would prohibit laboratory testing on all apes, including gibbons. This wouldn't have much of a direct impact since small apes are rarely studied in labs. But it would have symbolic importance. The petite, tree-dwelling gibbon may not be as easily anthropomorphized as its great ape cousins, but that's no reason to ignore it. In protecting the great apes, the Spaniards overlooked at least one vital human right: Freedom from discrimination based on appearance or lifestyle.

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