ECOLOGY OF NORTH AMERICAN RED SQUIRRELS ACROSS CONTRASTING HABITATS: RELATING NATAL DISPERSAL TO HABITAT

Because natal dispersal affects both individual fitness and population persistence, it is important to understand how dispersers are affected by habitat heterogeneity. To explore the effect of habitat on dispersal, we compared the ecology and natal dispersal of red squirrels (Tamiasciurus hudsonicus) originating from mature forest and adjacent commercially thinned forest. Because individuals living along the edge between the 2 forest types were more likely to have experience in both habitats, we classified squirrels according to habitat type (mature or thinned) and position (edge or deep within forest). Using livetrapping and radiotelemetry, we compared 4 habitats in terms of juvenile settlement patterns, surrogate measures of fitness, and population demography. Mature forest appeared to represent the highest quality habitat: mean density, mean overwinter survival, probability of surviving the field season, and success at raising ≥1 juveniles to emergence were higher in mature forest. However, the majority of juveniles from all habitats settled close to their natal territory, and with the exception of juveniles living along the edge of mature forest, juveniles settled within their habitat of origin. Juveniles living along mature edge biased their settlement for deep within mature forest. It appears that dispersal outcomes were affected by a combination of experience and opportunity. There are few, if any, other studies that have simultaneously compared demography, dispersal movements, and settlement patterns across contrasting habitats. While rare, studies such as this that link individual behavior and population theory are vital to effective population and landscape management.