Life in the Yukon can be tough for young red squirrels.
Freezing winters, food shortages, intense competition for territory and the threat of becoming prey to large predators such as the Canada lynx are just some of the trials they face.
The struggles and traumas of early life can literally take a toll on them and affect long-term survival, said Lauren Petrullo, an assistant professor in the Department of Ecology and Evolutionary Biology at the University of Arizona. Scientists want to know what factors, if any, can protect young squirrels against these threats.
Petrullo is part of the Kluane Red Squirrel Project, a long-term multi-university field project involving the University of Alberta, the University of Michigan, the University of Colorado Boulder, and the University of Saskatchewan. The project has tracked and studied thousands of wild North American red squirrels in the southwestern part of Canada’s Yukon Territory for more than 30 years.
A new study, which Petrullo led with David Delaney, a postdoctoral fellow at the University of Colorado Boulder, finds that the more challenges young squirrels face in the year of their birth, the shorter their adult lifespan.
Red squirrels that survive their first year of life live about 3 and a half years, on average, but early adversity can reduce life expectancy by at least 14%.
But there is a big caveat.
“The ecosystem that red squirrels inhabit in this region is unique,” Petrullo said. “Every three to seven years, their favorite food – the seeds of white spruce cones – is produced in superabundance during what we call a food boom. We found that these booms, although rare, can disrupt the biological integration of the former – Life Adversity If a squirrel had a difficult first year of life, if it was lucky enough to experience a food boom in its second year of life, it lived just as long, if not longer, despite its early life adversity.”
The team replicated a food boom by offering wild squirrels in the Yukon peanut butter as a supplemental food source. Peanut butter did not have the same effect as the natural food boom.
“This suggests that the buffering effect we see is actually not just about an increase in available calories,” Petrullo said. “These are probably changes in broader population-level dynamics, such as competition.”
What squirrels can teach us about humans
Petrullo and his colleagues are eager to discover the mechanisms that link early developmental conditions in squirrels to survival into old age. What they learn could also contribute to scientific understanding of human resilience.
“Our findings in red squirrels echo what we know about how early adversity can shorten adult lifespan in humans and other primates,” Petrullo said. “Humans vary widely in how vulnerable or resilient they are to the challenges they face during early development. Our study demonstrates that future environmental quality could be an important factor that may explain why some individuals appear to be more, or less , susceptible to the consequences of early life changes.
While it may be surprising that scientists can glean information about human resilience from wild red squirrels, Petrullo noted that squirrels are rodents, and rodents are commonly used as models for humans in laboratory settings.
“Many laboratory experiments have limited relevance to the broader dynamics between ecology and evolution, because it can be difficult to truly replicate the ecological challenges that animals have evolved to address in a laboratory setting,” he said.
Wild red squirrels, on the other hand, allow for this type of research and are an especially useful study group for questions related to the early-life environment, Petrullo said. Although growing up as a young squirrel in the Yukon can be difficult, as there are many things that hinder early development, there are also things that can go right.
“Some red squirrels are lucky to be born in milder early environments, similar to being born with a silver spoon,” Petrullo said. “Because of this, we have this really nice individual variation in early-life environmental quality in a natural ecological setting.”
However, this environment is expected to undergo major changes as global temperatures continue to rise.
“As food boom patterns begin to change,” Petrullo said, “the pathways connecting early experiences and lifespan may also change, potentially offering important insights into how animals can adapt to increasingly complex environments.” challenging.”