Artwork created by animals. We've followed the careers of various animal artists trained to create paintings and music (Ruby R.I.P.) and we believe that these works cannot be protected under U.S. copyright law. (P.S. for those seeking to invest in elephant art, watch out for the fakes!) According to the U.S. Copyright Office rules, only a human may create a 'work of authorship.' Those same rules prohibit registration of works owing their form solely to forces of nature and without human intervention -- such as driftwood. Although Copyright Office rules don't have the force of law -- the Copyright Act itself does not make these same anti-animal, anti-nature artist pronouncements -- these Copyright Office regulations are commonly accepted by the courts. For that reason, we believe that it would be difficult to (1) acquire a registration in the United States for the macaque self-portraits, and (2) for Slater's so-called assignees to maintain a lawsuit against an alleged infringer.
Photos in which a human did not press the shutter. There's a big difference between a photo taken by an animal and an "automatic," programmed, or computer-generated photo. For example, a photo taken with a timer can be copyrighted by the person who set up the camera and the timer. Similarly, a photo triggered by magnetic fields, or triggered by stroboscopic flashes, can also be copyrighted by the party who programmed the camera. By way of analogy, author Stephen Fishman points out in his "amazing treatise" on the public domain that the Copyright Office has registered hundreds of computer generated musical compositions and even a literary work written by a computer in the style of author Jacqueline Suzanne. In this manner if Slater had set up his camera to capture the "Cindy Sherman of Monkeys" and the shutter was programmed to capture the macaque each time it moved, Slater would arguably maintain copyright even though he was not present when the macaque said 'Cheese.'