Seismic linear clearings alter mammal abundance and community composition in boreal forest landscapes

Abstract

Habitat loss remains one of the primary threats to global forest communities but remaining forest habitats are also subjected to ongoing fragmentation by linear clearings such as seismic lines for petroleum exploration. Seismic lines alter local habitat use, but unlike roads, which are well studied, less is known about the effects of seismic lines on mammal abundance and community composition. The objective of this study was to determine whether fragmentation by seismic linear clearings affected mammal abundance or community composition at fine and landscape scales. Winter snow track surveys were conducted over three winters, within 14 landscapes, dispersed throughout a boreal forest area (4000 km2), to measure relative abundances of 17 co-existing mammals. Mammal communities within seismic line habitat were dissimilar from communities in nearby forest habitat and were characterized by relatively higher abundances of some larger herbivores (moose/elk) and some mammalian predators (cougar, lynx, weasel). Within broader landscapes (12.3 km2), relative abundances of some large mammals were also associated with seismic line fragmentation. One large predator (gray wolf) trended toward higher relative abundance in the landscapes most fragmented by seismic lines, while one large herbivore group (moose/elk) decreased in abundance in these landscapes. Overall, our results reveal that forest fragmentation by narrow linear clearings (e.g. seismic lines) had a measurable effect on wildlife relative abundances, particularly for a few large mammals. They also highlight the importance of differentiating between fine-scale and landscape-scale effects. In this area, strong preference and avoidance behaviors toward seismic line habitat, were generally not associated with a consistent response at the landscape scale, potentially due to the dissimilar responses by different species to seismic line habitats, which may have altered interactions between co-existing species, such as predator and prey species. These findings have important implications for the management of mammal communities located within forests fragmented by seismic lines.