Predation by Badgers on Columbian Ground Squirrels

Abstract

Predation by badgers ( Taxidea taxus ) on Columbian ground squirrels ( Spermophilus columbianus ), primarily pre-emergent juveniles, was documented in eastern Washington during 6 years. Badgers dug up the nest burrows of female ground squirrels each year, but frequency of attacks was biennial and high attack rates occurred only in the 3 years that one adult and one or more juvenile badgers were on the study area. Female ground squirrels usually survived attacks, but one or more juveniles eventually emerged from only 41% of the nest burrows dug up by a badger, compared to 90% for undisturbed nest burrows. Females and juveniles that survived a badger attack did not differ from their undisturbed counterparts in survival to the following year, and females appeared not to shift nest burrow sites in the following year in response to a badger attack. Although loss of juveniles to badger predation accounted for up to 56% of the estimated production of juveniles in a year, the population did not decline markedly after years of heavy predation. Higher survivorship of the smaller number of juveniles in those years was largely responsible for maintaining numbers the following year.