Michael was a silverback gorilla whose parents were killed while he was still a baby. According to the movie Koko: Conversation with a Gorilla, his handlers felt that using sign language, he was attempting to relate his mother's death at the hands of poachers. At the age of three he was brought to live with Koko at Stanford.
Koko, having seen videotapes of several males, expressed a desire to have a visit with Michael. Intended to be Koko's mate, she apparently came to relate to him as an adopted brother, and they never mated.
Michael's favorite color was yellow, and his favorite TV shows were Sesame Street and Mister Rogers. He enjoyed listening to Luciano Pavarotti and looking at pictures. Michael also greatly enjoyed painting, and took it quite seriously, as opposed to Koko, who would paint for fun. He died of heart failure. Koko and her more recent potential mate, Ndume, mourned their loss of Michael for several months after his death.
When an autistic teenager saw the painting, they sketched what they saw in the shape. It was an extremely close resemblance to a gorilla . When painting, Michael was always given a full palette and never restricted when it came to his use of colors or the way that he painted.
To paint, Michael often used his fingers, and sometimes a brush. Human artists have been envious of Michael's work, stating that it is far more uninhibited and pure than they could manage . Michael's work was considered impressionist -- and he seemed to enjoy painting images of things and events from his personal life, in a style that has been referred to by others as emotional representation.
In sign language, deaf humans often create new signs by combining or two or more signs, to express a concept for which they have no sign. Additionally, repetition and exaggeration of signs is used to create emphasis. Repetition, exaggeration and the creation of new signs by combining signs are techniques which are also used by simian 'signers'.
Michael learned 20 words within his first year with The Gorilla Foundation. The following is an example of Michael's description of an event that is thought by humans at The Gorilla Foundation to be the death of his mother -- killed by poachers when he was quite young:
Michael seemed to behave much like a small child. Some of the brightest gorillas have been assessed as having an IQ range of 75-90, whereas 100 is average for humans. Michael has described emotion, memories, and lies through sign language. Both Michael and Koko used the sign "fake" to describe a lie or to express doubt about the truth of a statement.