Horse fly and deer fly (Diptera: Tabanidae) species and abundance following logging in northwestern Ontario

Abstract

Horse flies and deer flies are important components of habitat for many species, but how logging may alter the communities of biting flies in the boreal forest is largely unexplored. Such knowledge is important to conservation, because biting flies can shape the behaviour and sometimes even the demography of vertebrates in the boreal forest. We compared the abundance and distribution of Tabanidae species in managed boreal forest stands in northwestern Ontario with three harvest histories. Using sweep nets during 2 summers, we collected specimens from forest stands that were young (harvested 20–35 years ago), intermediate (harvested 36–69 years ago), and old (unharvested or harvested ≥ 70 years ago). We tested the hypothesis that greater harassment potential in young stands was due not only to more abundant tabanids, but more abundant obligate blood-feeding (anautogenous) tabanids, which are more persistent in host seeking. We caught 8,895 specimens from 44 species. The oldest stands had the highest species richness, but the lowest abundance of individuals, whereas young stands had the highest relative abundance and the most anautogenous specimens, potentially causing more stress to hosts in young stands. These results demonstrate that forest harvesting may reduce habitat suitability for many large mammals due to an altered tabanid community.