Abstract and Summary

A three-year field-study of Richardson's ground squirrels was conducted to assess whether alarm calling functions to warn close relatives (“kin selection” hypothesis) or manipulate conspecifics (a “selfish” hypothesis). S. richardsonii had distinct calls for terrestrial and aerial predators, and the responses of squirrels varied appropriately according to the context of calls, implying that calling conveyed correct information concerning the nature of the danger. Alarm calling elicited by naturally occurring encounters with potential predators during 454 h of observation, and by a thrown frisbee in 70 experimental trials, was not equally probable for all age/sex classes. Squirrels were most likely to call when they had offspring or siblings nearby, which is supportive of the hypothesis that alarm calling is maintained by kin selection. Adult males, residing in the vicinity of either their probable progeny or their nonlittermate half-siblings, were the most likely age/sex class to call during the lactation period when young were below ground and were most vulnerable. I conclude that alarm calling by Richardson's ground squirrels is nepotistic rather than manipulative.