As It Happens

Koko, the gorilla who learned sign language, dies at 46

Animal psychologist Penny Patterson began working with Koko when the western lowland gorilla was just a year old. Despite attempts to pair her with a suitable mate, Koko never gave birth, but demonstrated a particular fondness for kittens.

'Her vocabulary is over 1,000 different signs,' Koko's trainer told As it Happens in 1991

Koko the gorilla, pictured here with her pet cat, has passed away at age 46. (CBC)

Even though she couldn't speak, Hanabiko the gorilla could converse quite fluently, and was more fluent in sign language than the average human.

Hanabiko  — better known by her nickname Koko — died on Tuesday in Woodside, California. She was 46.

Koko spent most of her life under the care and tutelage of animal psychologist Francine "Penny" Patterson, who taught her a modified version of American Sign Language (A.S.L.) — which she dubbed Gorilla Sign Language, or G.S.L.

Patterson had long hoped that Koko would give birth, although she never did. In 1991, she spoke with then-As it Happens host Michael Enright about the efforts to find Koko a suitable mate.

Here is some of their conversation.

Ms. Patterson, before we talk about Koko and her mate, let me understand — you used videotaping to find her a companion?

Well, yes. It wasn't exactly as though she got to pick the candidates that she liked, but it turned out that way.

According to The Gorilla Foundation, Koko used other ways besides sign language to communicate with her caregivers, including pointing to her choice of food with a pen, or using it to sketch something. (Ron Cohn/Gorilla Foundation)

How did you work that? What did you do?

When it became clear that Michael was not attractive to her as a mate, we showed her videotapes and also photographs of other male gorillas — mostly solitary gorillas who needed to be able to socialize again.

And she viewed the tapes, watched most of them, but turned her back on some of them — and even kissed the screen on one or two.

Tell me about Koko. Where was she born?

She was born at the San Francisco Zoo, on July 4th, 1971.

And you've been taking care of her almost from that date?

From a year from that date.

You've taught her American Sign Language?

Right. That was the purpose of the project, to see if a gorilla could learn gestural language. And she has proven that to be true.

Her vocabulary is probably over 1,000 different signs. We have still yet to chart the second 10 years of the project on the computer, so I can't give you an exact figure. But after the first 10 years, she had used almost 900 different signs.

The purpose of the project [was] to see if a gorilla could learn gestural language. And she has proven that to be true.-Animal psychologist Penny Patterson, Koko's longtime caregiver and trainer

That's extraordinary. Had you ever done this with a primate before?

No, I had read about projects that either used computer symbols or sign language, and I was very much impressed by those. And I wanted to pursue that line of research myself.

So she's obviously smart. Is she among the smarter gorillas?

I don't know. I would say she's probably average in intelligence, because she doesn't impress me as smarter than Michael, for instance. 

Michael is the 'ex', is he?


Why was he found wanting? What was his problem?

The problem is not with Michael. The problem is with Koko. Koko was reared with Michael. And female gorillas reared with males often reject them as mates, because of an incest taboo. In the jungle, they leave the group. And she isn't able to to do that here.

So what happened to Mike? It isn't his fault.

No, he's a wonderful silverback, a very handsome gorilla. And she just considers him like a brother.

For heaven's sake. Now you think it's appropriate for her to get pregnant and have a baby?

She thinks it's appropriate!

Now has her new-found friend that she got off the video dating service arrived?

He has arrived, a week ago. His name is Ndume.

And how are they getting along?

He's in quarantine right now. She can see him through a window. Today was the first day that he really came up to the window so that he could get a good look at his face. 

And she didn't want me to have anything to do with him after that, and told me I 'blew it' when I went up to the window. Whether this is jealousy or she thinks it's unfaithful, I don't know.

She in a sense gave you the finger, I guess.


Is it likely that her abilities with the language could be passed on to her offspring?

We think it would happen — partly because Koko has taken her little gorilla dolls' hands, and molded them to signs, such as "eat" and "drink" and "more".

Can she help Ndume with the signing?

We think she may model the signs to him. I don't know if she would actually mold his hands, because he's quite a big boy.

Well she's not after him for his mind anyway, is she?

Ha! Probably not.

Written by Kevin Ball. This interview first aired on As it Happens on December 18, 1991. Q&A edited for length and clarity.


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