Kin selection and adult female Richardson's ground squirrels: a test

Abstract

A population of adult female Richardson's ground squirrels (Spermophilus richardsonii) was experimentally manipulated so that on one half of the study area each of the 9 females had 2 or 3 closely related females (mother, daughter, or littermate sister) as neighbours (the "kin cluster group," KC), while the 10 females on the other half of the area did not have closely related females as contiguous neighbours (the "no kin cluster group," NKC). In the previous year, breeding success and behaviour of females on both halves of the study area were similar. Following the manipulation, KC females spent a greater proportion of their aboveground time feeding, were less vigilant, shared a greater proportion of their core area with their nearest neighbour, were less likely to be involved in interactions that led to chasing and fleeing, and had a much better breeding success compared with females in the NKC group. These results provide a preliminary demonstration that the association of adult female kin to Richardson's ground squirrels can be advantageous, and as such, the observed behavioural asymmetries based upon kinship could be maintained by kin selection.