There's also no inherent reason not to limit utilitarianism to humans. It also creates a nice clean conceptual boundary, so that increases descriptive utility.
This doesn't actually reflect my view, by the way.
Great apes (chimpanzees, gorillas, and orangutans)
Cetaceans (whales, dolphins, and porpoises)
Cephalopods (especially the octopus)
Other (please specify)