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Cross-Species Adoption

The tendency of adult animals to be nurturant toward babyish-looking animals might help explain why animals sometimes "adopt" the young of different species. This could be called cross-species adoption. For example, consider the following picture.

Boots the cat adopted bunnies found in the family's yard (photo by Odette Rauch-Auerbach, used by permission)

How could such a thing happen? Boots came from a humane society shelter with several kittens. They had just been given away when the bunnies were discovered in the yard. Presumably the cat responded to the cuteness of the baby bunnies, so the "mothering" program is activated instead of the "predator" program.

Why did Boots adopt the bunnies?

This is not just a fluke; I have a collection of similar illustrations. One shows a "broody hen" with abandoned kittens tucked under each wing. The kittens snuggled under the mother hen until they grew old enough to wander away.

Does it seem strange to think of a bird taking care of baby mammals? How about a pit bull taking care of baby birds? An illustration in Country magazine (April/May 1992, p.60) showed three baby turkeys in the loving care of a female pit bull.

Students have also contributed stories such as this one:

Once I was given three kittens who had been taken from their mother a few weeks too early. I brought the kittens home and my poodle-a female who had never had puppies-took to them immediately. I fed the kittens milk and they seemed to do very well. One day, I walked up on them and they were nursing my poodle. I might add that my poodle was not lactating. The kittens seemed as content as if they were being fed and my poodle really loved it! They played, ate and slept together, just as a little family does.

A couple of days later, I was playing with my poodle and I realized that the kittens had caused sores on my poodle. From then on I tried to get the kittens to stop and for my poodle to stop letting them nurse. I failed completely in every way and the sores were getting worse. The funny thing is my poodle didn't seem to mind them. Finally, as much as I hated it, I had to return the kittens to the original owner until they were much older. My poodle was very depressed for a few days, but she soon recovered with some extra love and attention. [Author's files]

What are possible explanations for this behavior?

There may occasionally be some genetic benefits to the misguided parents. For example, kittens that were "brooded" by a hen might not attack the hen's real chicks. Experiments have shown that cats who grow up with a particular type of rat will not attack other rats of the same species, so there is a general protection effect for similar animals. Cuty Boy, a cat who grew up with a parrot for a friend, refused to attack a bird that landed on the outside balcony of his apartment where his litter box is kept, according to his owner.

A sufficient reason for cross-species friendship might be the great importance of parenting instincts and positive social interactions in general, for many species. As with the stickleback that chases a red leaf, occasional "errors" are less important than having the right instincts.

Many more examples can be found at That web site specializes in images of different species cuddling, touching noses, sleeping together, and generally getting along peacably.

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