Sexually selected infanticide by male red squirrels in advance of a mast year

Abstract

North American red squirrels (Tamiasciurus hudsonicus) anticipate when white spruce (Picea glauca), their primary food source, will produce large amounts of cones in infrequent and irregular mast years (Boutin et al. 2006). Cones mature in autumn and are then available as food for red squirrels, but females produce larger, and often multiple, litters the preceding spring and summer in anticipation of the upcoming mast. Because this pulse of the cone food resource follows the birth of the litter, it cannot be a source of energy for the female to produce young; instead, there must be cues for increased reproductive investment by the females prior to mast cone production, perhaps through consumption of buds on the masting trees (Boutin et al. 2006, 2013). Boutin et al. (2006) only studied females; whether male behavior anticipates mast years is still unstudied. At our study area in the Yukon, 2014 was a mast year for spruce cone production in late summer (Lamontagne et al. 2005). J. A. Haines was observing male red squirrel mating behavior during spring 2014, giving her an unanticipated opportunity to document the previously unstudied effects of a mast year on male red squirrels.