So far, most of the interspecies relationships researchers have observed have happened in captivity—possibly because the probability of seeing one among zoo or household is just higher than happening upon it in the wild, but also because animals living in the world of humans are just more likely to interact with other species from a young age. There’s a reason so much of the Internet’s interspecies-friendship porn focuses on baby animals: The strongest bonds form early. Studies have shown that geese and ducks raised together will view each other as members of the same family; kittens raised with baby rats would never harm them. If a relationship takes root early enough in an animal’s social development, it can overrule instinct or later learned behavior. (The San Diego Zoo assigns “puppy buddies” to each of its cheetahs from birth, to help the cats learn to be more playful, and other zoos have similar programs.)
Another factor is surely that the animals raised by humans are getting fed. Animals, as C.S. Lewis put it, are always serious about food. But with that need out of the way, a kitten might find a baby rat fun to play with, without any intention of eating it.
Some researchers have made the case that predator and prey, stripped of the rules of the natural world, are actually well situated for friendship. “Predator and prey animals are already set up to know how to read each other,” said Donna Haraway, the author of When Species Meet. “Predators read prey animals incredible well, because it’s how they get dinner. And prey animals read predators very well, because it’s how they avoid becoming dinner.”
At this point, though, these theories are all just that: theories. “We don’t know” why animals form cross-species friendships, Bekoff said. More.
There’s something else, too. Some species play quite aggressively with others of their kind. Think “”horseplay,” as in the old-fashioned sign, “No horseplay around the pool.” Readers may have seen cats administer a “play” killing bite to the jugular to companion cats. But they stop.
If the prey animal is accepted as part of the pack (dogs) or sleeping colony (cats), it may simply be grandfathered by the more complex rules of within-group behaviour.
Note: Every few years, a tragically confused person decides that if all this is true, he can adopt and live with a bear or chimpanzee. No. If a cat ends up accidentally killing and eating his rat friend, it will not make the evening news. This does. Or this.
See also: What can we hope to learn about animal minds?
Are apes entering the Stone Age?
Researchers ask, Was early animal evolution co-operative? The new thesis suggests that the typical Ediacaran animals created an environment around them that enabled the more mobile creatures to evolve.
Follow UD News at Twitter!
“Interpecies porn,” as the Atlantic’s author Cairi Romm puts it: