Sex and scale: implications for habitat selection by Alaskan moose Alces alces gigas

We examined the roles of sex and spatial scale in habitat selection by Alaskan moose Alces alces gigas. We GPS-collared 11 female and seven male adult moose in the Tongass National Forest, Alaska, USA, during 2002-2004. We predicted that adult male and female moose would be spatially separated outside of the mating season, consistent with hypotheses attributing sexual segregation among sexually dimorphic ruminants to allometric differences in body and gastrointestinal size, and resulting differential needs for nutrient requirements by the sexes (the gastrocentric hypothesis), and varying risks of predation (the predation hypothesis) between sexes, especially for females with young. We predicted that habitat selection would be similar between sexes during the mating season, but dissimilar and occur at different scales during periods of late gestation and lactation. We expected that during segregation, females would select for a higher percentage of forested cover and a higher edge density than males to reduce predation risk on their young. Furthermore, we examined whether differences in scale of habitat selected between the sexes was related to home-range size. Multi-response Permutation Procedures (MRPP) analysis indicated that the spatial distributions of adult males and females differed, particularly near or during parturition. The sexes selected habitats similarly during the mating season (rut), when sexes generally were aggregated, whereas sexes exhibited differential habitat selection during spring, when sexes were segregated. Habitat selection by both sexes was best explained by vegetation and landscape composition tabulated within 1,000-m radii centered on GPS locations of moose. The sexes did not differ in the scale at which they selected habitats. Mean size of the annual home range was 76 km(2) for females and 125 km(2) for males, but size of home range was not related to scale of habitat selection by moose. Our results indicate that females were likely selecting habitat with high-quality forage while minimizing predation risk during periods of sexual segregation, whereas males were selecting habitat that allowed high forage intake, which together provide support for both the gastrocentric and the predation hypotheses.