DISPERSAL AND MIGRATION IN NORTHERN FOREST DEER - ARE THERE UNIFYING CONCEPTS?

Abstract

I summarize studies of natal dispersal and seasonal migrations in 5 species of forest deer: moose (Alces alces), roe deer (Capreolus capreolus), white-tailed deer (Odocoileus virginianus), mule deer (O. hemionus), and black-tailed deer (O. h. columbianus). Six main features of behavior characterize dispersal in these species: season of dispersal; biased or equal dispersal by the sexes; dispersal in relation to animal density; dispersal in the presence of adult aggression; pre-dispersal excursions; and dispersal distance. These traits are highly variable among and within species and also vary in their proximate causation: mate and resource competition; avoidance of inbreeding, and founder effect. Seasonal migrations are common to all 5 species. These movements are the result of many generations of summer dispersal, and a return to a traditional winter range. Although dispersal appears flexible in relation to different environmental conditions, seasonal migration is a more rigid system of behavior across species. Snow is a key triggering factor and determines occurrence and extent of migration. Snow depth and weather, not plant phenology, appear to determine onset of migration in spring and autumn. Also, the strong tradition in use of seasonal ranges are shared by the species. Summer range located at higher elevation than the winter range is typical of northern cervids in alpine landscapes. Nevertheless, more research is needed to understand relationships among altitude, range quality, and migration patterns of northern deer.