Koko the gorilla is one of few examples of a non-human animal which has had an explicit pet. Using sign language, she requested a cat; her first pet was a kitten named All Ball, to which she was reported to be quite attached and mourned for several days after the cat escaped and was killed by a car.
Raptors, such as eagles and falcons, must be handled very carefully to avoid attacks on their handlers; the sport of falconry is to a large extent ways of avoiding such outcomes, and so they are not really pets in the sense meant here. Large cats cannot become pets, as they do not reliably restrain their impulses (although cheetahs are an exception and have been kept as pets in the past). Nor do the large bears, for similar reasons. Small monkeys can be human companions, but they are notoriously unable to defer their curiosity which leads to much destruction. Several of the ferret and otter varieties can be human companions. Raccoons also fit this example. They adapt easily to almost any environment, but resist domestication.
