Abstract
Linear clearings for human activities cause internal fragmentation of otherwise intact native forest, with many potential impacts on wildlife. Across a boreal forest region of some 4,000 km2, we investigated how movements and habitat use of ecologically different mammal species are affected by narrow (about eight m) seismic line (SL) clearings associated with fossil fuel extraction, which form extensive networks many kilometers long. We conducted nine repeat snow track surveys during three winters at 14 pairs of one-kilometer transects, each comprising one transect along the SL and a second running perpendicular into adjacent forest. Data for 13 individually-analyzed mammal taxa (species or sets of closely related species) and five mammal groups, categorized based on body size-diet combinations, showed that movements across transects were either unaffected by SL clearings (relative to continuous forest) or restricted only slightly. However, these clearings were favored for linear travel by most species and body size-diet groups (excepting small mammals). The strength of this preference varied in a manner consistent with species’ differing needs to move long distances (associated with their energetic requirements): large predators > large herbivores > mid-sized predators > mid-sized herbivores > small mammals. In terms of overall habitat use, large-bodied predators (e.g., wolves and coyotes) strongly selected SL clearings over forest, medium-sized predators (e.g., mustelids) and medium-sized herbivores (e.g., hares and squirrels) preferred forest, and neither large herbivores nor small mammals had a clear habitat preference. Consequently, there was a net shift in both species and trophic composition within the SL, in favor of large predators and away from medium-sized predators and herbivores. Given the high regional SL density (1.9 km/km2) such shifts are likely to have complex ecological consequences, of currently unknown magnitude.
Highlights
Long and narrow clearings for human activities divide large forest tracts into multiple smaller patches, leading to a range of potential impacts on animals’ spatial behavior, How to cite this article Pattison CA, Catterall CP. 2019
Some mammal species preferentially use both road verges and non-road linear clearings because they provide either movement corridors (Gese, Dowd & Aubry, 2013; Tigner, Bayne & Boutin, 2014), or particular food resources (Morelli et al, 2014). Such preferential use for travel has been observed in some large predators, and can have further indirect effects on other mammal species which avoid areas near linear clearings to reduce the risk of predation (Dyer et al, 2001)
Our results indicate that non-road linear clearings in boreal forest did not reduce most species’ potential movements but instead increased them, especially for large predators and herbivores
Summary
Long and narrow clearings for human activities divide large forest tracts into multiple smaller patches, leading to a range of potential impacts on animals’ spatial behavior, How to cite this article Pattison CA, Catterall CP. 2019. Some mammal species preferentially use both road verges and non-road linear clearings because they provide either movement corridors (Gese, Dowd & Aubry, 2013; Tigner, Bayne & Boutin, 2014), or particular food resources (Morelli et al, 2014) Such preferential use for travel has been observed in some large predators, and can have further indirect effects on other mammal species which avoid areas near linear clearings to reduce the risk of predation (Dyer et al, 2001). Given this diversity of potential responses, evidence remains sparse about how various different mammal species within a forest community are impacted by non-road linear clearings
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