SPOKANE, Wash. (AP) – Washoe, a female chimpanzee believed to be the first nonhuman to acquire human language, has died of natural causes at the research institute where she was kept.

Washoe, who first learned a bit of American Sign Language in a research project in Nevada, had been living on Central Washington University’s Ellensburg campus since 1980. She had a vocabulary of about 250 words.

She died Tuesday night, according to Roger and Deborah Fouts, co-founders of The Chimpanzee and Human Communications Institute on the campus. She was born in Africa about 1965.

She was taken to the veterinary hospital at Washington State University on Wednesday for a necropsy. Her memorial will be Nov. 12.

Washoe also taught sign language to three younger chimps who remain at the institute, Central Washington spokeswoman Becky Watson said. They are Tatu, 31, Loulis, 29, and Dar, 31.

Washoe was the only chimpanzee at the institute born in Africa and was the matriarch of the chimpanzee family.

She was named for Washoe County, Nev., where she lived with Drs. Allen and Beatrix Gardner of the University of Nevada, Reno, from 1966 to 1970.

Primate researcher Jane Goodall, in Roger Fouts’ book “Next of Kin,” noted the importance of the work with Washoe.

“Roger, through his ongoing conversations with Washoe and her extended family, has opened a window into the cognitive workings of a chimpanzee’s mind that adds new dimension to our understanding,” Goodall was quoted as saying.

In 1967, the Gardners established Project Washoe to teach the chimp ASL. Previous attempts to teach chimpanzees to imitate vocal languages had failed. Roger Fouts was a graduate student of the Gardners.

For Washoe to be considered “reliable” on a sign, it had to be seen by three different observers in three separate instances. Then it had to be seen 15 days in a row to be added to her sign list.

But there was controversy over whether the chimp was really using ASL. Cognitive scientist Steven Pinker has contended the notion that Washoe was the first non-human to acquire a human language was without scientific support.