Meeting Abstract
Social animals face trade-offs between the costs and benefits of group living. Parasite transmission is a widely-recognized cost of sociality because hosts often suffer from dual costs of parasites acting as stressors and/or vectors for disease. Despite these important fitness consequences, little is known about the social mechanisms facilitating the spread of ectoparasites from one individual to another in wildlife populations. Here, we studied the spread of fleas across free-living California ground squirrels, Otospermophilus beecheyi. O. beecheyi forage and socialize above ground, but seek refuge from predators in underground burrows. Importantly, there are documented cases of the fleas found on O. beecheyi carrying the bacterium, Yersinia pestis, the causative agent of plague. Thus, revealing modes of flea transmission in this species has important implications for the study of social evolution as well as for management of zoonotic diseases. In the field, we regularly live-trapped, marked and released squirrels at their points of capture. Upon its first capture of each week, we systematically combed each individual squirrel to sample and collect its fleas. Our results reveal consistent, individual differences in mean ectoparasite loads across time beyond those predicted by age and sex. We are currently analyzing the basal “stress” hormones of these individuals. We are also using social network statistics to test two, non-mutually exclusive hypotheses: 1) space-use overlap hypothesis and 2) social transmission hypothesis to determine whether spatial or social interactions best explain individual differences in flea numbers. Taken together, our results will reveal the importance of host traits in shaping parasite and disease networks in wildlife populations.
