Why Red Squirrels Depend on Good Neighbors

Even though red squirrels are loners, living near familiar neighbors helps them survive.

In a new study published in Current Biology, researchers measured the year to year survival rate of North American red squirrels that are part of the Kluane Red Squirrel Project, based in the southwest Yukon of Canada. They found that squirrels that kept the same neighbors outweighed any negative impacts of growing a year older.

“Red squirrels are a solitary, territorial species. This means that both males and females defend exclusive territories year-round and rarely physically interact with one another,” lead author Erin Siracusa of the Centre for Research in Animal Behaviour at the University of Exeter, tells Treehugger.

“However, it is important to recognize that while red squirrels may be ‘solitary’ this does not necessarily make them ‘asocial.' Red squirrels often interact socially with their territory neighbours by communicating through vocalizations called ‘rattles’ which they use to defend their homes.”

Red squirrels each defend their territory with their food stash at the center. It’s easy to assume that squirrels only compete and don’t cooperate with other squirrels nearby, but researchers found that isn’t the case.

“Red squirrels must compete for food, space, and mates with other squirrels to survive and reproduce. So, we normally think about neighbours as having a negative impact on red squirrels,” Siracusa says.

“But in this study, we found that when squirrels live next to their neighbours for long enough, they can actually become ‘friends.’ Under these circumstances red squirrels can actually benefit from their neighbours as individuals with familiar neighbours produce more offspring and survive longer.”

Being familiar with their neighbors is mutually beneficial because after a while, they aren’t on guard all the time and begin to trust each other somewhat.

Siracusa explains it in human-like terms.

“So, imagine if you just moved into a new house. You don't know any of your neighbours and so you might not trust them. This means you're probably going to be cautious about locking your doors at night or making sure your security cameras are on when you go away for holiday,” she says.

“But the longer you live next to these same neighbours the more you get to know them and trust them. You know that your neighbours are not going to break into your house or steal from you and so you can relax your defences.”

The same thing happens for squirrels, she says. When they live next to each other year after year, they also become familiar with each other and are more trusting.

“These long-term neighbours enter into a 'gentleman's agreement' about territory borders which allows them to reduce the time and energy involved in negotiating and renegotiating territorial boundaries or getting involved in costly fights,” Siracusa says.

At some point, the squirrels decide that it’s much more beneficial to cooperate rather than compete with their competitors. Siracusa says that decision is one of the really exciting takeaways from the study.

“We are talking about an animal whose interactions with its neighbours, are for all practical purposes, fundamentally competitive. Red squirrels defend exclusive territories — they compete with their neighbours for food, space, and mates. But what we are suggesting here is that because familiar neighbours are so important to reproductive success and survival it might actually be beneficial for a red squirrel to help keep its neighbours alive,” she says.

“So, this raises the interesting possibility that red squirrels might cooperate with their competitors. What this cooperation might look like – we don’t know yet. Squirrels might share food with their familiar neighbours, alarm call to warn them of predators or even form defensive coalitions to prevent potential usurpers from taking over territories. These are all interesting avenues for future research.”

Kin vs. Familiarity

The study covered the "neighborhood" within 130 meters (425 feet) of a central territory. It used 22 years of data more than 1,000 squirrels in the Kluane Red Squirrel Project. Researchers looked at “kinship,” which is how closely related the squirrels were, as well as “familiarity,” which is how long the squirrels occupied adjacent territories.

They found, to their surprise, that living near related squirrels had no effect on health. Living near neighbors they knew, however, increased both their survival year-to-year and their reproductive success. 

These benefits were particularly strong later on in life for squirrels 4 years old or older, they found. At that age, the benefits of familiarity offset any age-related drops in survival or reproductive success.

“I think this raises really an interesting question about the role of social relationships in the aging process, because what this means, in theory, is that maintaining stable social relationships (i.e. familiarity) with territory neighbours into later life has the potential to increase the longevity of squirrels and delay senescence,” Siracusa says.

“In other words, social relationships could be the squirrel's key to anti-aging!”