Sex-specific hoarding behavior in North American red squirrels (Tamiasciurus hudsonicus)

In short-term hoarding rodents, reproduction and hoarding often overlap and reproductive status can alter hoarding behavior. In long-term hoarders these activities are often separated seasonally. Therefore, annual and sex-specific variation in the timing of reproduction relative to the hoarding season may influence variation in the hoarding behavior of long-term hoarders. North American red squirrels (Tamiasciurus hudsonicus) clip and hoard white spruce (Picea glauca) cones each autumn, but have variation in reproductive timing such that in some years the hoarding season overlaps with reproductive activity. Over 4 years with naturally varying cone availability we quantified reproductive timing and hoarding behavior. Males completed mating 22–90 days before the onset of hoarding, whereas large numbers (45–86%) of females during large cone crop years weaned litters after hoarding commenced. Despite these differences in reproductive timing, across all years females clipped more cones than did males, whereas males hoarded more cones and had a higher propensity to larder-hoard than did females. Interestingly, in the years with large cone crops, females that weaned their litters later (during the hoarding season) did not have reduced hoarding or reproductive performance (offspring growth and recruitment) than females that weaned their litters earlier. In the year with the most extensive overlap between female reproduction and hoarding, lactating females did not differ from males in the amount of time they allocated to hoarding. In this year, the daily energy expenditure of lactating females during the hoarding season did not differ from that of males engaged in hoarding or from that of lactating females prior to the hoarding season. Hence, under high-resource conditions the competing demands of lactation and hoarding can both be sustained, allowing red squirrels flexibility in the separation between reproduction and hoarding.