THE SEASONALITY OF A MIGRATORY MOOSE POPULATION IN NORTHERN YUKON

Dorothy Cooley, Heather Clarke, Shel Graupe, Manuelle Landry-Cuerrier, Trevor Lantz, Heather Milligan, Troy Pretzlaw, Guillaume Larocque, Murray M. Humphries

Abstract


At the northern edge of their North American range, moose (Alces alces) occupy treeline and shrub tundra environments characterized by extreme seasonality. Here we describe aspects of the seasonal ecology of a northern Yukon moose population that summers in Old Crow Flats, a thermokarst wetland complex, and winters in surrounding alpine habitat. We collared 19 moose (10 adult males and 9 adult females) fitted with GPS radio-collars in Old Crow Flats during summer, and monitored their year-round habitat use, associated environmental conditions, and movements for 2 years. Seventeen of 19 moose were classified as migratory, leaving Old Crow Flats between August and November and returning in April to July, and spent winter in alpine habitats either northwest (n = 8), west (n = 4), or southeast (n = 5) of Old Crow Flats. The straight-line migration distance between summer and winter ranges ranged from 59 to 144 km, averaging 27 km further for bulls than cows. In summer, 18 of 19 moose situated their home ranges in and around drained lake basins and shallow lake habitats within Old Crow Flats. In winter, moose at elevations < 400 m selected for river, shrub, or drained lake habitats, whereas those at elevations >600 m selected for shrubby valley bottoms near lakes and rivers within home ranges dominated by alpine tundra. Moose at high elevations marginally reduced their exposure to cold extremes due to the prevalence of thermal inversions, but cold avoidance was not a strong driver of habitat selection, including for moose at low elevations. Stable isotope signatures of moose hair, aquatic plants, and terrestrial plants were consistent with a year-round, shrub-dominated diet characterized by slight habitat- and season-associated dietary differences. Local knowledge of the Vuntut Gwitchin First Nation predicted several of our major results, including 1) summer home range fidelity, 2) selection of lakeshore habitats, 3) use of drained lake basins, 4) dietary reliance on shrubs and emergent vegetation, and 5) responses to contemporary environmental changes. Although the core habitat of this moose population, including the winter ranges of its 3 subpopulations, is well protected by a variety of special management units, parks, and protected areas in Yukon and Alaska, pronounced climate warming is dramatically impacting this thermokarst wetland. Coordinated monitoring, management, and conservation of this unique landscape, moose population, and socio-ecological system is warranted.

Full Text:

PDF