( Gloucestershire-based photographer David Slater was in Indonesia in 2011 attempting to get the perfect image of a crested black macaque when one of the animals came up to investigate his equipment, hijacked his camera and took hundreds of selfies. One of those selfies is now famous.
Copyright law, which is a minefield in itself, says that the person who takes a photograph owns the copyright (regardless of who owns the camera it was taken on). Of course monkeys aren't people - yet, but it's an interesting grey area.