Squirrels show softer side by adopting orphaned pups

TORONTO - The squirrels you often see fighting over scraps may not seem

altruistic, but they have a softer side too — seen occasionally when they adopt orphaned kin.

The study by Andrew McAdam, professor at Guelph University, 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 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, doctoral 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 adoption scenarios, the pups were nieces, nephews, siblings or grandchildren to

the adoptive mother.

By examining the breeding records of thousands of squirrels over the past 20 years,

McAdam was able to calculate the costs of adoption.

“What we found was that squirrels will only adopt an orphaned pup when the costs of

adoption are low and when the orphans carry a large percentage of the same genes

such as siblings, nieces or nephews rather than more distant relatives,” said McAdam.

What’s also remarkable is that squirrels are able to assess which pups are related or

not, he added, according to a Guelph University release.

“We suspect that, if they find pups on the territory, they remember that their neighbour was a relative and carry the pups back to their nest. This would be quite intelligent behaviour for a squirrel,” concluded McAdam.

These findings were published in Nature Communications.