Ecology of woodland caribou in central Manitoba : implications for forestry practices

Woodland caribou (Rangifer tarandus caribou) in the boreal forest are believed to be threatened by human encroachment and associated disturbances such as resource exploration and extraction. Fifteen female woodland caribou were radiocollared and monitored in central Manitoba, from 1995 to 1997, to obtain information on their population range and distribution, movements, and habitat use in relation to forestry concerns. The population ranged over 4 600 km² within a large peatland system and concentrated their activities in two areas for both the summer and winter seasons. Females were relatively more solitary during the summer and exhibited fidelity to specific calving and summering areas averaging 83.4 km². Individual wintering locations varied between years and among individuals. Post-rut and pre-calving mixed-sex aggregations were observed on the southern portion of the herds range. Caribou from the northern part of the range utilized a traditional travel corridor moving as far as 65 km to access the aggregation areas and their summer or winter ranges. Adult survival during the study period was high, averaging 90%. Survival of the 1995 cohort also appeared to be high as indicated by the 0.65:1 calf-cow ratio, and 30% calf composition of observed caribou in the autumn of 1995. The annual rate of change (λ) of 1.19 from January to November of 1995 indicated that the population was increasing at that time. Habitat selection analyses at the home range level revealed that female woodland caribou preferred lowland black spruce to most other habitats except peatlands and jack pine. During the spring and summer at the third order of selection, females exhibited preferences for both lowland black spruce and treed peatlands while avoiding cutovers. Data for the autumn and winter suggested that lowlands and peatlands were heavily utilized during those months. Though occasional use of young cutovers was noted, woodland caribou tended to avoid harvested sites. As a result of past logging practices three main habitat types were available to caribou: young stands less than five years of age with little regenerating vegetation, stands dominated by trembling aspen with a secondary component of softwoods, and jack pine dominated stands. Due to the young age and high deciduous content of most regenerating stands; habitats created by logging were better suited for moose than woodland caribou.

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