Understanding how individuals change their behaviors as they age is useful for research on many different animal species, including humans. By clarifying the consequences of senescence for aging individuals, such studies could also provide new insights into how societal structure and function might change as the population ages.
A research team led by the University of Oxford has now studied a population of aging female wild red deer on the Isle of Rum in Scotland. The analysis revealed that aging deer become less sociable with age and tend to adopt a life of solitude in their advancing years.
“We found that deer’s social networks shrink as they grow old and begin associating less with others,” said study lead author Greg Albery, a biologist at Oxford. “This ‘social aging’ appears to be driven by older individuals choosing to live in more isolated locations and engaging with fewer other deer within these sparser areas.”
Dr. Albery and his colleagues applied novel social network analysis methods to a large, 46-year-long dataset containing observations of over 3,500 female deer over their lifetimes. As these deer grew older, they began interacting with fewer conspecifics within their home ranges, and often shifted their locations to less populated areas of their habitat. Moreover, they had smaller home ranges, farther away from the center of the population, in areas of lower density with lower-quality grazing opportunities.
“This new evidence of social aging in the wild shows the value of long-term datasets. By tracking many individuals simultaneously over their entire lives, we can understand how and why their social associations with one another change over time,” said study senior author Josh Firth, a professor of Biology at Oxford.
Further research is needed to clarify why aging deer become less social. The scientists currently hypothesize that social aging is driven by a combination of multiple factors, including moving to areas that are easier for older individuals to forage in, and changing their behavior to become more socially selective in their relationships with other deer. Applying the scientific methods employed in this study to other long-term data sets of wild animals will help generate a broader view of the fundamental rules that govern aging and social behavior in natural populations.
The study is published in the journal Nature Ecology & Evolution.