Squirrels Show Softer Side by Adopting Orphans

http://www.sciencedaily.com/releases/2010/06/100601114631.htm

ScienceDaily (June 2, 2010) — Those neighbourhood squirrels you often see fighting over food may not seem altruistic, but new University of Guelph research has found that the critters will actually take in orphaned relatives.

The study by Guelph Prof. Andrew McAdam, along with researchers from the University of Alberta and McGill University, revealed that red squirrels will adopt pups that have lost their mother.

It's a significant finding because while such adoptions are typical among species that live in extended family groups, it's much less common among asocial animals, such as squirrels.

"Social animals, including lions and chimpanzees, are often surrounded by relatives, so it's not surprising that a female would adopt an orphaned family member because they have already spent a lot of time together," said McAdam, an evolutionary biologist. "But red squirrels live in complete isolation and are very territorial. The only time they will allow another squirrel on their territory is the one day a year when the females are ready to mate or when they are nursing their pups."

But the study, published in Nature Communications, also found that squirrels have their altruistic limits. They will adopt only if the orphans are related, and even then it's a rare occurrence.

Over two decades, the research team has come across only five cases of adoption.

"That's five cases out of the thousands of litters that have been born since the project began," said McAdam. "Adoption does happen, but it's rare."

Jamie Gorrell, a PhD candidate at the University of Alberta, identified 34 cases of potential adoption over 20 years. An adoption is possible only if the mother dies and a nearby squirrel is also nursing.

"We discovered relatedness plays a critical role in whether a neighbouring squirrel will adopt or not," said McAdam.

In all five adoption scenarios, the pups were nieces, nephews, siblings or grandchildren to the adoptive mother.

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