Red Squirrel (Tamiasciurus hudsonicus) feeding on Balsam Poplar (Populus balsamifera) galls induced by aphids

Abstract

Red Squirrel (Tamiasciurus hudsonicus) specializes in feeding on conifer cone seeds but will feed opportunistically on a wide variety of other food items, including fungi, eggs, small vertebrates, and invertebrates. In much of their range, Red Squirrels experience fluctuations in the availability of their primary diet (conifer seeds) seasonally and annually because of variation in seed production. We document a seemingly uncommon or unreported feeding behaviour by a Red Squirrel in a year of an exceedingly low conifer cone production in Yukon, Canada: a squirrel foraging for and feeding on aphids hidden within galls formed on Balsam Poplar (Populus balsamifera). We searched for community-reported observations of Red Squirrels through iNaturalist and found additional evidence of apparently similar gall feeding behaviour elsewhere in Canada. We estimate that aphids can be a substantial source of caloric energy for Red Squirrels. Our observation represents another example of the diet breadth of Red Squirrels during periods of low conifer seed availability.