Tucson Standard

Life for young red squirrels in the Yukon is challenging, with harsh winters, scarce food, and predators like the Canada lynx posing significant threats. According to Lauren Petrullo, an assistant professor at the University of Arizona's Department of Ecology and Evolutionary Biology, early-life trauma can impact long-term survival. Scientists are investigating factors that might help young squirrels overcome these challenges.

Petrullo is involved in the Kluane Red Squirrel Project, a long-term study conducted by multiple universities including the University of Alberta, University of Michigan, University of Colorado Boulder, and University of Saskatchewan. This project has observed thousands of North American red squirrels in Canada's Yukon territory over three decades.

A recent study published in Proceedings of the Royal Society B: Biological Sciences led by Petrullo and David Delaney from the University of Colorado Boulder reveals that early challenges reduce adult lifespan. Red squirrels typically live about 3.5 years if they survive their first year, but adversity can shorten this by at least 14%.

Petrullo noted a unique aspect of the squirrel's ecosystem: "Every three to seven years, their favorite food – seed from cones of white spruce trees – is produced in superabundance during what we call a food boom." These booms can mitigate early-life adversity effects. If a squirrel experiences a food boom after a tough first year, it may live as long or longer than those without such adversity.

The team tried replicating this effect by providing peanut butter as supplemental food but found it did not have the same impact as natural food booms. "This suggests that the buffering effect we see is not really just about an increase in available calories," Petrullo explained. "It's probably about shifts in larger population-level dynamics, like competition."

Petrullo and her colleagues aim to understand how early conditions affect later survival in squirrels and potentially humans. She stated, "Our findings in red squirrels echo what we know about how early-life adversity can shorten adult lifespan in humans and other primates."

While surprising to some that insights into human resilience could come from wild red squirrels, Petrullo highlighted that rodents are often used as models for humans in labs. However, lab experiments may not fully replicate ecological challenges animals face naturally.

Wild red squirrels provide valuable data on early-life environments due to individual variations across natural settings. "Some red squirrels have the luck of being born into gentler early environments," said Petrullo.

Climate change poses additional concerns as global temperatures rise. Petrullo warned that changing food boom patterns might alter how early experiences affect lifespan: "As food boom patterns begin to change... pathways that connect early-life experiences and lifespan may change as well."