Testing the parasite-mediated competition hypothesis between sympatric northern and southern flying squirrels

Paul P O'Brien; Jeff Bowman; Sasha L Newar; Colin J Garroway

doi:10.1016/j.ijppaw.2021.11.001

Testing the parasite-mediated competition hypothesis between sympatric northern and southern flying squirrels

Int J Parasitol Parasites Wildl. 2021 Dec 17:17:83-90. doi: 10.1016/j.ijppaw.2021.11.001. eCollection 2022 Apr.

Authors

Paul P O'Brien¹, Jeff Bowman^{2

3}, Sasha L Newar², Colin J Garroway¹

Affiliations

¹ Department of Biological Sciences, University of Manitoba, Sifton Road, Winnipeg, Manitoba, R3T 2N2, Canada.
² Environmental & Life Sciences Graduate Program, Trent University, 1600 West Bank Drive, Peterborough, Ontario, K9L 0G2, Canada.
³ Wildlife Research & Monitoring Section, Ontario Ministry of Northern Development, Mines, Natural Resources & Forestry, Trent University, 2140 East Bank Drive, Peterborough, Ontario, K9L 0G2, Canada.

Abstract

Competition is a driving factor in shaping ecological communities and may act directly or indirectly through apparent competition. We examined a classic example of parasite-mediated competition between northern (Glaucomys sabrinus) and southern flying squirrels (G. volans) via the intestinal nematode, Strongyloides robustus, and tested whether it could act as a species barrier in a flying squirrel hybrid zone. We live-trapped flying squirrels (G. sabrinus and G. volans), grey squirrels (Sciurus carolinensis), red squirrels (Tamiasciurus hudsonicus), and chipmunks (Tamias striatus) from June-September 2019 at 30 woodlots in Ontario, Canada. Fecal samples from squirrels were collected and analyzed for the presence of endoparasite eggs. For each individual, we calculated Scaled Mass Index (SMI) as a measure of body condition to assess the effect of S. robustus on squirrels. We found eggs of S. robustus in all species except chipmunks. Infection with S. robustus did not appear to affect body condition of southern flying squirrels and grey squirrels, but we did find a weak negative effect on northern flying squirrels and red squirrels. Despite a weak asymmetric effect of S. robustus on flying squirrels, we did not find any evidence that parasite-mediated competition could lead to competitive exclusion from woodlots. Furthermore, S. robustus eggs were common in feces of the red squirrel, a species largely sympatric with northern flying squirrel.

Keywords: Apparent competition; Glaucomys sabrinus; Glaucomys volans; Parasitism; Secondary contact; Strongyloides robustus.