Movements, Survival, and Settlement of Red Squirrel (Tamiasciurus Hudsonicus) Offspring

Movements and settlement patterns of animal offspring, along with the costs of occupying familiar and unfamiliar habitats, have been inferred frequently, but rarely have they been documented directly. To obtain such information, we monitored the individual fates of 205 (94%) of the 219 offspring born over 3 yr in a population of the North American red squirrel (Tamiasciurus hudsonicus), at Fort Assiniboine, Alberta, Canada, (54.20°N, 114.45°W). We located neonates by radio—tracking mother squirrels, and thereafter we documented the movements, survival, and settlement patterns of the offspring, using a combination of telemetry, live—trapping, and visual observations. Prior to settlement, offspring made forays of up to 900 m (° = 126 m) off the natal territory, but they did not abandon the natal territory until they had settled on their own territory. Foray distance was not related to the age or size of the offspring. We used the locations of offspring kills to show that the risk of predation significantly increased when the offspring were travelling off of their natal territories. Just under half of the 73 offspring that acquired territories did so no or immediately adjacent to their mother's; the farthest settlement distance was only 323 m from the natal territory, or about the distance of three territory widths. Movement data from adults in the population showed that all offspring settled within potential contact of their mother (and possibly their father). Offspring that settled relatively farther away from their natal territory were more likely to obtain larger territories, with traditional hoarding and overwintering sites (middens). These offspring also had higher overwinter survival, suggesting that the costs of making forays off the natal territory may be balanced by the advantages of locating a superior territory.