SPACING, MOVEMENTS, AND HABITAT SELECTION OF THE RIVER OTTER IN BOREAL ALBERTA

Seasonal spacing patterns, home ranges, and movements of river otters (Lontra canadensis) were studied in boreal Alberta by means of radiote lemetry. Adult males occupied significantly larger annual home ranges than adult females. Males' ranges overlapped those of females and also each other's. In winter, home ranges of males shrank and showed less overlap. Otters often associated in groups, the core members typically being adult females with young, or adult males. Otters tended to be m ore solitary in winter. In winter, movement rates of all sex and age c lasses were similar, and much reduced for males compared with those in other seasons. These data indicated a strong limiting effect of winte r ice on behaviour and dispersion. We tested the hypothesis that otter s select water bodies in winter on the basis of the suitability of sho reline substrate and morphology for dens with access both to air and t o water under ice. Intensity of selection was greatest in winter, with avoidance of gradually sloping shorelines of sand or gravel. Adults s elected bog lakes with banked shores containing semiaquatic mammal bur rows, and lakes with beaver lodges. Subadults selected beaver-impounde d streams. Apart from human harvest, winter habitats and food availabi lity in such habitats are likely the two factors most strongly limitin g otter density in boreal Alberta.