"Researcher Penny Patterson met Koko, a one-year-old gorilla, at San Fransisco Zoo in 1972 and since then the two have rarely parted. Koko, like other apes, has been taught sign language for the deaf and has come up with some remarkable inventions.

One of his first creations was when a woodpecker was drumming nearby. Koko's teacher signed 'Koko, listen bird.' Koko held the sign for 'bird', looked at his teacher and raised his eyebrows. With this gesture he had turned a statement into a question; then, having established that he understood, he gave the woodpecker it's gorilla-style name, 'listen bird.'

On another occasion, Koko was asked about death. The conversation went as follows:

Teacher: Where do gorillas go when they die?
Koko: Comfortable hole, bye.
Teacher: When do gorillas die?
Koko: Trouble old. And tigers.
Teacher: Don't like tigers?
Koko: Frown bad red.
Teacher: I like tigers.
Koko: Tiger nail rough.
Teacher: What animals do you like?
Koko: Gorilla love."

--The Earth, Its Wonders, Its Secrets: Intelligence in Animals (1994)