Stairway to heaven or highway to hell? How characteristics of forest roads shape their use by large mammals in the boreal forest

Abstract

Decades of expansion of industrial resource extraction in boreal forests have resulted in the legacy of thousands of kilometers of linear features (seismic lines, forest roads) that have fragmented several wildlife habitats. The decommissioning of anthropogenic linear features and the restoration of suitable habitat are top priorities for the recovery of several species at risk, among which, the threatened populations of boreal caribou (Rangifer tarandus caribou). However, the decommissioning of linear features found in caribou range is expensive, and determining which characteristics make them more beneficial to caribou predators and competitors could assist in prioritizing those that may be most critical for boreal caribou habitat restoration. We thus aimed to determine how fine-scale forest road characteristics influence their use by gray wolf (Canis lupus), black bear (Ursus americanus), moose (Alces americanus) and caribou. We used camera traps and generalized linear mixed models to test the effect of road-scale characteristics on the use of forest roads by wolves, bears and moose while also considering larger-scale covariates. Wolves had a greater probability of using roads that were surrounded by wetlands and had a low lateral cover density. For bears, the intensity of use was lower on 20+ year-old roads when compared to 0–10-year-old roads, and higher on roads surrounded by coniferous stands. Moose intensity of use was higher on 11–20-year-old roads and lower on 30+ year-old roads, and decreased on roads surrounded by clearcuts and with a lower number of deciduous stems growing on them. We could not test for caribou use as we did not capture enough events. Nevertheless, by showing which forest roads are more used by caribou predators (wolves and bears) and its apparent competitor (moose), our study highlights the importance of considering both road-scale characteristics and the landscape context in which roads are built to prioritize the most detrimental roads to caribou conservation and guide efficient restoration efforts of its habitat.