A feel-good tale of sperm whales "adopting" a deformed bottlenose dolphin made an Internet splash this week. The story resonated with readers, including Reddit commenter Fallapoo, who said: "I see a Disney movie in the works."
But the marine mammals aren't the only ones that form odd alliances, experts say.
Such adoptions are relatively common among domestic animals, and occasionally seen in the wild, according to Jenny Holland, author of the 2011 book Unlikely Friendships . (Read a Q&A with Holland about her book.)
And in her forthcoming book, Unlikely Loves, Holland will feature a Dalmatian that adopts a calf that happens to wear Dalmatian-like spots, a goat that helps a young giraffe learn self-confidence, and a hen that sits on "her" pups to keep them warm.
But what motivates these adoptive families?
"I wish I could crawl into these animals' minds and ask! But we can make some educated guesses based on what we know about animal brains—and our own," said Holland, a National Geographic contributing writer. (Read about how animals are smarter than you think.)
For instance, in some cases, an animal will adopt one of its own species, which is instinctual.
"Instinctively animals take care of young to help them survive and therefore pass on the...