CEB Committe on Evolutionary Biology

Spotlight : Katie Brooks

Katie Brooks

Katie Brooks at her field site near Mammoth Lakes, CA. 

I study benefits of sociality in a community of Belding’s ground squirrels, a species that lives in alpine and sub-alpine meadows in the northwestern United States. Because this species lives in high alpine meadows that are covered in snow for most of the year (my field site is located at 9,300 feet above sea level), individuals hibernate for roughly eight months per year. Such a long hibernation creates specific energetic demands: if squirrels do not gain enough weight before the end of summer, they will starve and die overwinter. However, squirrels cannot only think about gaining weight for hibernation.  They must also avoid predation attempts from red-tailed hawks, kestrels, coyotes, weasels, pine martens, bobcats and badgers.

These conflicting demands create an ideal system for studying how social relationships among squirrels may increase their chances of survival. In this species, males disperse away from the population in which they are born, whereas females stay behind and therefore live amongst their female relatives. A study completed in the 1970’s demonstrated that females alarm call to warn their relatives of predators. My dissertation work is building on this study to determine what other benefits females receive from living amongst kin as well as how males and females benefit from non-kin relationships.     

Over the past five years, I have found that squirrels gain anti-predatory benefits from kin and non-kin relationships. For example, squirrels that live in more densely populated areas of the field site spend less time watching for predators, which allows them to spend more time foraging. Squirrels that forage more also gain more weight over the summer and have a better chance of surviving the winter hibernation. Females with kin also spend less time watching for predators than those who do not have any kin alive in the meadow. Females with kin also have lower stress hormone levels. This relationship may exist because they trust that their relatives will alarm call to warn them of nearby predators.

My research is based at the Sierra Nevada Aquatic Research Lab (SNARL) and Rock Creek Canyon near Mammoth Lakes, CA.  Spending my summers here has been incredible! The mountains are beautiful and the area offers many hiking opportunities. Because my field site is at such a high elevation, I often start the season in snowshoes and full winter clothing! By mid-June, however, the meadow is covered in wildflowers and the weather is very pleasant.  We typically begin the day at 8:00am by recording behavioral observations on individual squirrels.  Then we spend a few hours trapping the squirrels to weigh them, collect fecal samples for stress hormone measures and blood samples for immune function measures.  We also mark the squirrels with black hair dye in distinctive patterns so that we can see who’s who from far away. 

Please visit my website and my lab’s website for more information.

Connect with Katie Brooks.