Spatial Distribution of Yearlings in a Richardson's Ground Squirrel Population

Yearlings constituted 56%—67% of an adult Richardson's ground squirrel population in southern Saskatchewan. On the average 101 female yearlings were located 64 m from their site of original capture as young. Whether or not the mother was present after hibernation did not affect the distance moved by female yearlings. If the mother was present the average distance between mother and her female yearling offspring on closest capture dates was 40 m. Six male yearlings whose mothers did not survive hibernation were 25 m from their site of original capture as young, compared with 353 m for three male yearlings whose mothers did survive. Twenty—eight male yearlings whose mothers were unknown fell into two groups: 18 that moved less than 150 m from original caputure site (average 63 m) and 10 that moved more than 150 m (average 439 m). Laboratory experiments established that mothers and yearlings are able to identify each other as familiar or unfamiliar after a 7—8 month separation over hibernation. The data suggest that for a full understanding of the organization of adult ground squirrel populations the relationships between the animals must be known.