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Kanzi the bonobo is quite the musician. Image courtesy of the Great Ape Trust

In the new movie Rise of the Planet of the Apes, the leader of the ape revolution can talk. In the real world, apes can’t speak; they have thinner tongues and a higher larynx, or vocal box, than people, making it hard for them to pronounce vowel sounds. But that doesn’t necessarily mean they don’t have the capacity for language—sign language, after all, doesn’t require any vocalization.

Over the years, researchers have succeeded—and failed—in teaching apes to use language. Here’s a look at some of the more famous “talking” apes.

Viki: Viki, a chimpanzee, came closest to being a real talking ape. In the late 1940s and early 1950s, Keith and Catherine Hayes of the Yerkes Laboratories of Primate Biology, then located in Orange Park, Florida, adopted Viki and raised her at home as if she were a human baby. With the Hayeses moving her lips for her, Viki learned to utter “mama.” Eventually, with much difficulty, she managed to say three other words—papa, cup and up—on her own. Viki’s tenure as a talking ape didn’t last long; she died at the age of seven of viral meningitis.

Washoe: In the 1960s, psychologists Allen and Beatrix Gardner of the University of Nevada, Reno recognized that chimpanzees naturally gesture a lot and thought chimps would be well suited for sign language. In 1966, they started working with Washoe. Later, psychologists Roger and Deborah Fouts, now retired from Central Washington University, continued the work. By the end of Washoe’s life in 2007, she knew about 250 signs and could put different signs together to make simple combinations like “Gimmie Sweet” and “You Me Go Out Hurry.” Washoe’s adopted son Loulis also learned to sign—by watching his mother. He was the first ape to learn signs from other apes, not humans. For more on Washoe’s life, read Roger Fouts’ Next of Kin.

Nim: After the success with Washoe, psychologist Herbert Terrace of Columbia University decided to replicate the project. At first, Nim—full name Nim Chimpsky, named after linguist Noam Chomsky who thought language was unique to humans—was raised in a human household. (Washoe had been treated like a person too but had her own trailer.) Later, Nim was removed from the family and his language lessons moved to a lab on Columbia’s campus. In the end, Terrace concluded Nim never really learned language; he had merely been trained to imitate his teachers to get rewards. The sad story of Nim’s life after the project ended is told in the new documentary Project Nim.

Chantek: Chimpanzees are not the only talking apes. In 1978, anthropologist Lyn Miles of the University of Tennessee at Chattanooga began studying an orangutan named Chantek. During eight years of study, Chantek learned 150 signs. He also showed signs of being self-aware: he could recognize himself in a mirror. Today, you can visit Chantek at Zoo Atlanta, his home since 1997.

Koko: Koko the gorilla is probably best known for her love of kittens and Mr. Rogers (and maybe less well-known for her encounter with Captain James T. Kirk). Koko’s sign-language training began in 1972 with then-graduate student Francine (Penny) Patterson of Stanford University. According to the Gorilla Foundation, Koko knows 1,000 signs and understands spoken English. It also claims the gorilla has an IQ somewhere between 70 and 95 (the average human IQ is 100). (Critics, however, remain skeptical about some of Koko’s supposed abilities due to the lack of recent scientific publications supporting the claims. (PDF))

Kanzi: Kanzi, a bonobo, doesn’t use sign language; he uses different combinations of lexigrams, or symbols, to communicate. In the early 1980s, psychologist Sue Savage-Rumbaugh, then of Georgia State University, was trying to teach Kanzi’s mom, Matata, to use the lexigrams; instead, Kanzi was the one who mastered the symbols. Kanzi understands spoken English and knows close to 400 symbols. When he “speaks,” his lexigram usage follows rules of grammar and syntax, according to researchers at the Great Ape Trust in Iowa, where Kanzi now resides. Kanzi is also an accomplished stone-tool maker.

A young gorilla in the Hirwa group in Rwanda, 2009 (courtesy of flickr user petercolesdc)

On the one hand, it’s pretty amazing that I can find images of a specific mountain gorilla family in Rwanda through a simple Flickr search. But the availability of those photos comes from the numerous visits of humans to the national parks in Congo, Rwanda and Uganda where the world’s remaining 786 mountain gorillas live, and those visits may have a deadly downside for the gorillas: respiratory infections from human viruses.

Mountain gorillas (Gorilla berengei berengei) live only in the mountainous region where Congo, Rwanda and Uganda meet, and their small numbers make them vulnerable to extinction. To make matters worse, they are sandwiched between some of the most populous areas of Africa, and threatened by habitat destruction and poaching. A lesser known problem is infectious disease, which is the second biggest cause of death for the gorillas, after trauma, and accounts for one fifth of all sudden deaths.

And now a study in the journal Emerging Infectious Diseases documents two gorilla deaths from the human metapneumovirus (HMPV) in 2009. During that summer, the Hirwa family of gorillas in Rwanda experienced an outbreak of respiratory disease; 11 of the 12 animals experienced symptoms including coughing, nasal discharge and lethargy. Veterinarians from the Mountain Gorilla Veterinary Project treated five of the gorillas with antimicrobial drugs, but an untreated adult female and a 3-day-old male died. Analyses of the remains revealed that both individuals had been infected with HMPV, though the adult female died of a secondary bacterial pneumonia infection. The HMPV infection likely predisposed her to pneumonia, the researchers say.

“Because there are fewer than 800 living mountain gorillas, each individual is critically important to the survival of their species,” said Mike Cranfield, executive director of the Mountain Gorilla Veterinary Project. “But mountain gorillas are surrounded by people, and this discovery makes it clear that living in protected national parks is not a barrier to human diseases.”

The source of the HMPV is unknown, and the two animals that died had not been handled by any of the veterinarians or park staff during the course of their illness. But with the human population ever encroaching and tourists visiting them in their mountain homes, it seems better strategies are needed to protect the gorillas from human diseases.