Vulnerable caribou and moose populations display varying responses to mountain pine beetle outbreaks and management

Abstract

Rising global temperatures and changing landscape conditions have led to widespread mountain pine beetle (Dendroctonus ponderosae) outbreaks in western North America. Pine beetle management is typically implemented to mitigate economic losses, but its effects on wildlife, particularly ecologically important species like caribou (Rangifer tarandus) and moose (Alces alces), warrant greater attention. We assessed the effects of early-stage pine beetle infestation, timber harvest, and fire on habitat selection by caribou (boreal and central mountain designatable units) and moose in west-central Alberta, Canada. Using global positioning system (GPS) collar data collected 3–5 years after infestation, we developed resource selection functions and functional response models. Caribou exhibited seasonally variable responses, generally avoiding pine beetle-affected areas in winter but selecting them in summer. They also avoided harvested and burned areas, though this avoidance depended on overall disturbance levels within their ranges. Moose displayed sex-specific responses to pine beetle infestations and associated management: females avoided pine beetle-affected areas but selected burned sites year-round, while males showed the opposite pattern. These findings suggest that pine beetle disturbances may negatively affect caribou and female moose winter habitat availability while simultaneously enhancing conditions for male moose. Further research is needed to disentangle the individual and cumulative effects of pine beetle management actions versus general timber harvests and wildfires, as these disturbances may be compounding rather than acting in isolation.