RED SQUIRRELS (TAMIASCIURUS HUDSONICUS) FEEDING ON SPRUCE BARK BEETLES (DENDROCTONUS RUFIPENNIS): ENERGETIC AND ECOLOGICAL IMPLICATIONS

Abstract

We report the novel occurrence of North American red squirrels (Tamiasciurus hudsonicus) feeding on spruce bark beetle (Dendroctonus rufipennis) larvae, and consider the energetic and ecological implications. Although a bark beetle outbreak was 1st noted at our study site in 1994, significant feeding on them by red squirrels was not observed until 2002, after which there was significant increase in the prevalence of autumn beetle foraging by squirrels into 2003. This increase corresponded with a decrease in spruce seed availability, the squirrels' preferred food source. Spruce bark beetles currently represent an important food source, with 73% of monitored squirrels engaged in beetle feeding in autumn 2003, providing 20% of daily energy requirements. In autumn 2002 and 2003, the density of beetle-infested trees on a squirrel's territory was a significant predictor of whether it fed on beetle larvae but not the proportion of its foraging bouts involving bark beetles. Feeding on larval spruce bark beetles by red squirrels represents a short-term solution to a climate-mediated beetle outbreak that will ultimately reduce local spruce seed production and habitat suitability for red squirrels.