Characterization of woodland caribou (Rangifer tarandus caribou) calving habitat in the boreal plains and boreal shield ecozones of Manitoba and Saskatchewan

Abstract

The concept of residence, as defined by the Canadian Species at Risk Act, and its application to calving sites for woodland caribou (Rangifer tarandus caribou) has been grounds for recent debate. At the centre of this debate are questions focussing on our lack of knowledge surrounding calving duration, site identification, site fidelity and the importance of the pre-calving and post-calving periods. To better understand the spatial, temporal and landscape characteristics of calving sites and calving seasons for boreal caribou, we analyzed the movement pattern of 31 animals in the boreal plains and boreal shield ecozones. Telemetry data from 31 females in the boreal plains and boreal shield ecozones (12 from the Kississing-Naosap (K-N) herd in Manitoba between 2002 and 2005, and 19 from the Smoothstone-Wapaweka animals (S-W) in Saskatchewan), between 2005 and 2007, were analysed.Using a LOESS curve, eight distinct seasons were identified for both groups. Using GPS telemetry data, reduced movement rates of 50 m/h or less for a minimum of a week were used to identify 33 calving sites in the Smoothstone-Wapaweka animals and 13 calving sites in the Kississing-Naosap herd. The calving season extended from April 29th to June 7th for the Smoothstone-Wapaweka animals and from May 4th to May 29th for the Kississing-Naosap herd. At that time, the spatial extent of their movements was also reduced, corresponding to a mean area of 0.16 km2 for the Smoothstone-Wapaweka animals and 0.05 km2 for the Kississing-Naosap herd. Analysis of several spatial scales was performed to determine the degree of hierarchical habitat selection occurring at and around calving. The three scales used were the seasonal range scale, the calving period scale and the calving site scale. The seasonal range scale was defined as those areas occupied during the spring, calving and summer seasons, the calving period scale was defined as those areas occupied during the pre-calving, calving and post-calving periods and the calving site scale was defined as the area occupied during the calving period. To identify the main factors influencing habitat selection at the calving site scale, distances to jack pine, black spruce, treed muskeg, roads, cuts and other habitat variables were computed and analysed using condtional-logistic regression while generalized estimating equations were used to evaluate selection of the same factors at the seasonal range and calving periods scales. Caribou were selective of habitat type at the seasonal range and calving periods scales with distance to jack pine, treed muskeg and hardwood stands having considerable influence on habitat selection. Using model results, predictive maps were developed and applied to the respective landscapes. Through a better understanding of behavioural strategies of woodland caribou at calving, and through the use of predictive modelling and predictive mapping, existing and potential calving sites can be identified. This will increase the efficiency and ability of managers to provide an appropriate degree of protection to calving sites and will allow them to better manage activities occurring within the areas.