Intraspecific cache pilferage by larder-hoarding red squirrels (Tamiasciurus hudsonicus)

Although cases of pilfering food are reported commonly in the mammal literature, the factors affecting pilfering rates among individuals and between populations within the same species remain relatively unknown. We measured individual pilfering rates in 2 populations of highly territorial larder-hoarding red squirrels (Tamiasciurus hudsonicus) in Kluane, Yukon, Canada. One population received artificial food supplementation (where all individuals had ad libitum food) and had a 2-fold higher density than the control population. We knew the age, relatedness, and spatial relationship of all individuals in each population, and we had a measure of the food resources (cones) cached by each individual and their fates through the study. Results from experimental removal of territory owners suggested that younger squirrels with smaller food caches were more likely to pilfer when provided the opportunity. However, using a mark-recapture study of marked spruce cones under natural conditions, we found that few individuals (14%) pilfered, and stolen cones represented only 0.3% of total cones that were larder-hoarded. Pilfering occurs at a much lower rate in Kluane than reported for red squirrels in other regions and is less than rates reported for scatter-hoarding species.