Home range size, habitat selection, and mycophagy of sympatric North American flying squirrels

The northern flying squirrel (Glaucomys sabrinus) is a mycophagous specialist (i.e., having a fungi-dominated diet) which might be displaced following northward range expansion by the congeneric southern flying squirrel (Glaucomys volans). Loss of the northern flying squirrel could, in turn, limit fungi spore dispersal in forest communities. To understand the potential implications of squirrel species turnover on fungal dispersal, we investigated the home ranges, habitat selection, and fungi consumption of the two flying squirrel species living in sympatry in Ontario, Canada. We live-trapped flying squirrels for more than one year (2020–2021), deployed 31 radio collars (northern, n = 13; southern, n = 18), and radio-tracked individuals to investigate home range size. We also collected fecal pellets to quantify fungi in the squirrels' diet. Both squirrel species had similar home range sizes, and there was evidence of considerable home-range overlap between the species. Habitat selection analysis using a binomial generalized linear model of mean selection ratios indicated that southern flying squirrels selected deciduous-dominated habitats more than northern flying squirrels did within their home ranges and that both species selected pine-oak-barren habitats. Finally, we identified that northern flying squirrels had significantly higher spore loads and spore richness in their scat than their southern counterparts. Nevertheless, southern flying squirrels consumed fungi during each season. We conclude that the two squirrel species share many aspects of the landscape but habitat partitioning and differences in diet between species facilitated sympatry. Southern flying squirrels do make a contribution to spore dispersal at this location through fungus consumption and relatively large home ranges.