Trucks vs treks: The relative influence of motorized vs non-motorized recreation on a mammal community

Outdoor recreation is increasing rapidly on public lands, with potential consequences for wildlife communities. Recreation can induce shifts in wildlife activity and habitat use, but responses vary widely even within the same species, suggesting mitigating factors that remain poorly understood. Both the type of recreation – motorized or non-motorized – and the distance of wildlife from human disturbance may be important in developing a general understanding of recreation impacts on wildlife and making more informed management decisions. We conducted a camera-trapping survey in the Colville National Forest (CNF) of northeastern Washington in the summers of 2019 and 2020. We collected ~11,000 trap nights of spatially-extensive data on nine mid-large mammalian species, simultaneously recording the presence and activity patterns of motorized (primarily vehicles on roads) and non-motorized (primarily hikers on trails) recreation and wildlife both along trails and roads and off trails and roads (away from most recreation). We used diel overlap analysis, time lag analysis, and single-season single-species occupancy modeling to examine the impact of recreation on the focal species. Species temporally avoided recreationists either by shifting to more nocturnal hours or delaying return to recently-used recreation sites. Most species also responded spatially by altering use or intensity of use of cameras sites due to recreation, though both positive and negative associations with recreation were documented. Species’ responded to non-motorized recreation (e.g., hikers on trails) more often than motorized recreation (e.g., vehicles on roads). Most effects of recreation extended off the trail or road, though in three instances the spatio-temporal response of species to recreation along trails/roads disappeared a short distance away from those features. Our work suggests that a better understanding of landscape-scale impacts of recreation, including fitness consequences, will require additional work to disentangle the effects of different types of recreation and estimating the effective distance at which wildlife responds. Moreover, these results suggest that quiet, non-consumptive recreation may warrant increased attention from land managers given its potential to influence spatiotemporal ecology of numerous species.