Anthropologist Barbara King from the College of William & Mary says she and other scientists have documented a number of animals, ranging from dogs to hippos to apes, that make bonds with animals of another species. If one dies, the survivor grieves. An elephant named Tarra was close to a dog named Bella and grieved after Bella was killed by coyotes. King says she has also been moved by the relationship between Owen the hippo and a 100-year-old tortoise named Mzee. “In this friendship that formed over years, they worked out a system of cross-species communications,” says King. In some cases, the biggest risk in cross-species friendships isn’t getting eaten. It’s emotional loss.

This is excellent fodder for Pixar films and children stories.