Caribou nursery site habitat characteristics in two northern Ontario parks

Natasha L Carr,Arthur R Rodgers,Shannon C Walshe

doi:10.7557/2.27.4.343

Abstract

To prevent further range recession, habitat features essential to the life-history requisites of woodland caribou (Rangifer tarandus caribou) such as calving and nursery sites need to be protected for the persistence of the species. Woodland caribou may minimize predation risk during calving by either spacing out or spacing away from predators in the forest to calve on islands, wetlands, or shorelines. Our objective was to determine the characteristics of shoreline habitats used as calving and nursery sites by female woodland caribou in northern Ontario. Detailed vegetation and other site characteristics were measured at nursery sites used by cow-calf pairs in Wabakimi and Woodland Caribou Provincial Parks for comparison with shoreline sites that were not used by caribou within each park. Differences in habitat variables selected by female caribou in the two study areas reflect broad ecoregional differences in vegetation and topography. In Wabakimi Provincial Park, understorey tree density and ground detection distance played key roles in distinguishing nursery sites from sites that were not used. In Woodland Caribou Provincial Park, groundcover vegetation and shrub density were important in the selection of nursery sites by female caribou. Generally, female caribou in both parks selected nursery sites with greater slope, lower shrub density but thicker groundcover vegetation, including greater lichen abundance, and higher densities of mature trees than shoreline sites that were not used. The identification of these important features for caribou nursery sites provides a basis for improving their protection in future management policies and legislation.

Highlights

In Ontario, woodland caribou (Rangifer tarandus caribou) range of continuous occupancy has receded further north since the late 1800s (Racey & Armstrong, 2000). This recession is mainly attributed to habitat loss through anthropogenic disturbance and Schaefer (2003) estimates that, at the current rate, forest-dwelling woodland caribou will be extirpated from Ontario in 90 years
We removed the 1-2 m ground detection distance variable from both models and used the remaining 17 variables for further Discriminant Function Analysis (DFA) analyses. The results of both the multivariate analysis of variance (MANOVA) and DFA suggested there were greater differences between the two parks than between nursery and absence sites within each, so we developed separate Resource Selection Functions (Boyce et al, 2002) for each park following the model selection procedure suggested by Shtatland et al (2003)
The density of overstorey trees and canopy cover were higher at nursery sites than unused absence sites in both Woodland Caribou and Wabakimi Provincial Parks, suggesting selection of nursery sites in oldergrowth forests of both ecoregions

Summary

Introduction

In Ontario, woodland caribou (Rangifer tarandus caribou) range of continuous occupancy has receded further north since the late 1800s (Racey & Armstrong, 2000). This recession is mainly attributed to habitat loss through anthropogenic disturbance and Schaefer (2003) estimates that, at the current rate, forest-dwelling woodland caribou will be extirpated from Ontario in 90 years. Caribou have evolved space-use strategies to avoid predation (Bergerud et al, 1990; Rettie and Messier, 2001), which is considered the main proximate factor of population limitation of woodland caribou across North America (Bergerud, 1974; Seip, 1992; Ouellet et al, 1996; Stuart-Smith et al, 1997; Rettie & Messier, 1998). Predators can kill more than 50% of young ungulates in free-ranging populations

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