Dec. 17 (UPI) -- North American red squirrels benefit from maintaining the same neighbors, year after year.
According to a new study, published Thursday in the journal Current Biology, the advantages of neighborhood stability outweighed the negative impacts of growing a year older.
Researchers also determined living near relatives offers squirrels no benefits.
"These squirrels are solitary -- each defending a territory with a 'midden' (food stash) at the center -- so we might assume they don't cooperate," lead author Erin Siracusa said in a news release.
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"However, our findings suggest that -- far from breeding contempt -- familiarity with neighbors is mutually beneficial," said Siracusa, an expert in animal behavior and a professor at the University of Exeter.
Playing defense is difficult. It takes time and energy, resources that could be used to find food and potential mates. The trade-off may explain why squirrels that maintain the same neighbors tend to fare better than those who don't.
For the study, Siracusa and her research partners analyzed 22 years of data on squirrels living in the forests of Yukon, Canada, within the traditional territory of the Champagne and Aishihik First Nations.
The data was collected as part of the Kluane Red Squirrel Project, which looked at the kinship of nearby squirrels, as well as their familiarity -- how long squirrels lived alongside the same squirrels.
When researchers compared survivability and reproduction rates with the kinship and familiarity of squirrels with their neighbors, they found squirrels who kept the same neighbors were more likely to avoid death and had greater reproductive success.
Males with greater familiarity with their neighbors produced more pups, while females with greater familiarity had more of their pups survive the winter.
"It may be that, after a certain time living next to one another, squirrels reach a sort of 'agreement' on boundaries, reducing the need for aggression," Siracusa said. "Competition is the rule in nature, but the benefits identified here might explain the evolution of cooperation even among adversarial neighbors."
When looking at the risks associated with growing a year older, researchers revealed a harsh reality. Four-year-old squirrels had a 68 percent chance of surviving the following year, while five-year-old squirrels had only a 59 percent chance.
However, five-year-old squirrels who kept the same neighbors had a 74 percent chance of surviving the year.
"Although we don't have evidence of direct cooperation among familiar neighbors -- such as working together to fight off an intruder -- it's clear that neither benefits if their neighbors die," Siracusa said.
"Whatever the nature of their interactions, our study shows that even solitary species have important social relationships," Siracusa said.
Although researchers found new benefit to kinship, it is possible kinship levels are simply too low to impact the data one way or the other.
Previous studies have shown related squirrels are less likely to make aggressive rattling sounds at one another, and will sometimes even share a nest to survive the winter.
