Life in the Yukon presents numerous challenges for young red squirrels, including frigid winters, food scarcity, intense competition for territories, and the threat of predation by large predators like the Canada lynx. These factors can have a lasting impact on the squirrels’ long-term survival, with early-life struggles and trauma affecting their adult lifespan. The Kluane Red Squirrel Project, a long-term field project involving multiple universities, has been studying wild North American red squirrels in the Yukon for over 30 years to better understand these dynamics.
A recent study led by Lauren Petrullo and David Delaney found that the more challenges young squirrels face in the year they are born, the shorter their adult lifespan. While red squirrels typically live about 3 1/2 years if they survive their first year, early-life adversity can reduce life expectancy by at least 14%. However, the study also revealed an interesting caveat – food booms, where the squirrels’ favorite food becomes superabundant every three to seven years, can offset the negative effects of early-life adversity on lifespan.
The team replicated a food boom by offering wild squirrels peanut butter as a supplemental food source, but this did not have the same impact as the naturally occurring food boom. This suggests that the buffering effect seen in squirrels is not just about an increase in available calories, but likely involves larger population-level dynamics such as competition. Understanding these mechanisms could provide valuable insights into human resilience, as early-life adversity can also impact adult lifespan in humans and other primates.
While it may seem surprising that insights about human resilience can be gained from studying wild red squirrels, rodents like squirrels are often used as models for humans in laboratory settings. Wild red squirrels offer a unique opportunity to study the interplay between ecology and evolution, as they face ecological challenges that are difficult to replicate in a lab. The varying early-life environmental quality experienced by red squirrels in their natural habitat can shed light on how individuals respond to adversity and how environmental quality influences survival.
As the global climate continues to change, the Yukon’s environment is expected to undergo significant shifts. Changes in food boom patterns could alter the pathways connecting early-life experiences and lifespan in red squirrels, providing valuable insights into how animals adapt to increasingly challenging environments. By studying how red squirrels navigate the complexities of their natural habitat, scientists hope to gain a better understanding of resilience and survival strategies that could be applicable to a broader understanding of human health and longevity. Despite the challenges young squirrels face in the Yukon, there is also the possibility for luck and favorable environmental conditions to support their growth and survival.
