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.