Seasonal and yearly changes in consumption of hypogeous fungi by northern flying squirrels and red squirrels in old-growth forest, New Brunswick

Abstract

Seasonal consumption of mycorrhizal fungus by northern flying squirrels ('Glaucomys sabrinus') and red squirrels ('Tamiasciurus hudsonicus') was examined in old-growth mixedwood forest at Fundy National Park in southern New Brunswick between May 1999 and March 2001. Using faecal pellet analysis, we found that the amount of fungus in the diet of both species was dependent on season and year of study and ranged from 35% to 95%. Twenty fungal taxa, most of them hypogeous Ascomycetes and Basidiomycetes, were detected in diets. More taxa were detected in summer diets compared with all other seasons, but all seasonal samples contained several hypogeous taxa. Up to six taxa were identified in any one sample. Both squirrel species occurred at high densities throughout the study, and dietary overlap between them was great throughout this time in terms of both the amount of fungus and the proportions of different taxa that were consumed. Overall, our data suggest that both 'G. sabrinus' and 'T. hudsonicus' are abundant and important consumers of fungus in the region and that fungus may represent a key food resource, particularly during times when other foods are limited.