Environmental Influences on Infanticide in Columbian Ground Squirrels

Infanticide of preweaned and weanling juvenile Columbian ground squirrels ( Spermophilus columbianus ) has been previously reported, but its prevalence in most populations is poorly known. I examined evidence of infanticide in a six‐year study of four populations in southwestern Alberta, two of which received an experimental supplementation of food for two years. Evidence of infanticide of weanling ground squirrels was uncommon, except for one population and year (previously supplemented population at 1580 m elevation in 1984) in which 9 dead young were found, suggesting an increased rate of infanticide. The rate of total loss of pre‐weaned litters also increased at 1580 m in 1984. At higher elevation sites (2100 m), however, no evidence of infanticide was found under experimental or unmanipulated conditions. One factor that might have influenced the rate of infanticide of weanlings was their degree of development when they first emerged from natal burrows. A review of studies of 11 populations of Columbian ground squirrels suggested that under natural conditions, infanticide may have differed among environments. Differences in density among populations appeared to have little influence on the rate of infanticide, but elevation was significantly negatively associated with infanticide.