Potential Role of Parasites in Squirrel and Woodrat Decline in Appalachians
Climate change and habitat loss alter the landscape for wildlife, resulting in shifts in geographic ranges, occupation of smaller, remnant habitat patches, or use of novel environments. These processes often lead to sympatry between species that historically were non-sympatric. Such interactions increase competition for resources and expose species to novel parasites that reduce a species’ fitness leading to wildlife declines. We explore these interactions in species of endangered North American rodents—Northern flying squirrels (Glaucomys sabrinus) and Allegheny woodrats (Neotoma magister). Northern flying squirrels are declining in the United States due to competition with its congener, southern flying squirrels (Glaucomys volans). Evidence indicates that competition is mediated by a shared nematode, Strongyloides robustus. Transmission of this nematode to northern flying squirrels is increasing due to forest fragmentation and climate change. We also note the recent discovery of S. robustus as a novel parasite and a factor in the decline of the European red squirrel (Sciurus vulgaris). Likewise, in Allegheny woodrats, shrinking landscape changes have resulted in increased range overlap with raccoons (Procyon lotor) that harbor a nematode fatal to woodrats. The subsequent transmission of this nematode, Baylisascaris procyonis, to woodrats is a contributing factor to woodrat decline throughout the Appalachians.
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