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Family relationships may play an important role in helping animals survive in the wild, but their benefits can depend on age and sex. A new study conducted by researchers at the University of Chicago examined how social relationships, physical condition, and environmental factors influence the survival of Belding’s ground squirrels (Urocitellus beldingi). These small mammals inhabit mountain meadows in western North America and spend much of the year hibernating. Female ground squirrels typically remain near their birthplace and live alongside close relatives, while males usually move away. Researchers wanted to understand whether having more family members nearby increases an individual’s chances of surviving from one year to the next.

The researchers analyzed more than two decades of field observations from a population of Belding’s ground squirrels in Rock Creek Canyon, California. They collected information about the animals’ age, sex, body weight, reproductive activity, family relationships, stress-related hormones, and seasonal snowfall. Individual squirrels were identified and monitored across multiple years to determine which animals survived. The researchers then used statistical models to examine how these factors were associated with survival. Their findings showed that heavier adult squirrels were generally more likely to survive, suggesting that having sufficient energy reserves is particularly important for animals that depend on stored body fat during hibernation. Lower levels of stress-related hormone metabolites were also associated with better survival among adult females and juvenile squirrels.

One of the most interesting discoveries involved the different effects of family relationships on adult and young female squirrels. Adult females with more close female relatives, including mothers, sisters, and daughters, had higher chances of surviving into the following year. The researchers suggested that cooperation among relatives, such as warning one another about predators and defending shared territories, might explain this advantage. However, the opposite relationship appeared among juvenile females. Each additional close female relative was associated with approximately 15% lower odds of survival, possibly because younger squirrels face greater competition for food, shelter, and other resources. Male survival, meanwhile, showed no significant relationship with the number of close female relatives. These findings suggest that living near family members can provide advantages during adulthood while potentially creating challenges earlier in life.

The study also revealed that seasonal environmental conditions influence survival. Young squirrels that emerged earlier in the season were more likely to survive, potentially because they had more time to grow and accumulate fat before hibernation. Lower snowfall during the preceding winter was associated with better survival among adult females, possibly because earlier snowmelt allowed more time for feeding and reproduction. However, this does not necessarily mean that declining snowfall benefits ground squirrel populations over the long term. The research highlights how animal survival results from a complex combination of social behavior, physical condition, and environmental changes. Because the study was observational, it cannot establish that these factors directly caused the differences in survival. Nevertheless, its findings provide valuable insights into how family relationships and seasonal conditions may influence the persistence of wildlife populations in changing mountain environments.

References

Mateo, J. M., Brooks, K. C., & Dosmann, A. (2026). Kin count: Social, physiological, and environmental correlates of annual survival in Belding’s ground squirrels. PLOS ONE, 21(11), e0358786. https://doi.org/10.1371/journal.pone.0358786

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