Censusing 13-Lined Ground Squirrels with Adult and Young Alarm Calls

Abstract

Recorded adult and simulated young alarm calls of 13-lined ground squirrels (Spermophilus tridecemlineatus) were played to 3 populations from April to October 1975. The adult alarm call evoked an erect posture, making it possible to count an average of 83 percent of the population number determined by snaring. Lactating females hearing the simulated young alarm call responded by approaching the sound source. Population census and counts of lactating females facilitated determination of population mortality and projection of population levels after litter emergence. J. WILDL. MANAGE. 41(4):755-759 For centuries man has mimicked animal calls to lure a food source within his weapon's effective range (Densmore 1929:129). Though such calls still are used widely by sportsmen to decoy game, only recently have auditory cues been used to census wildlife. Diem (1954) used a fawn call to determine if an observed doe had young in the vicinity, and Stirling and Bendell (1966) used playbacks of female blue grouse (Dendragapus obscurus) precopulatory calls to census male grouse. In both instances animals formerly hidden from view made their presence known and were counted easily. Thirteen-lined ground squirrel populations, though usually inhabiting open fields, are difficult to assess. Individuals constantly are moving into and out of their burrows and only rarely will the majority of the population be seen above ground. The object of this study was to show how auditory cues can be used not only to census 13-lined ground squirrel populations, but also to determine reproductive success and the resulting population growth from counts of lactating females. I gratefully acknowledge the Zoology Department of The Ohio State University for furnishing the equipment used in this study. I thank Dr. D. J. Borror for his advice and instruction throughout the project.