Habitat selection by wolves and mountain lions during summer in western Montana

Abstract

In the Northern Rockies of the United States, predators like wolves (Canis lupus) and mountain lions (Puma concolor) have been implicated in fluctuations or declines in populations of game species like elk (Cervus canadensis) and mule deer (Odocoileus hemionus). In particular, local distributions of these predators may affect ungulate behavior, use of space, and dynamics. Our goal was to develop generalizable predictions of habitat selection by wolves and mountain lions across western Montana. We hypothesized both predator species would select habitat that maximized their chances of encountering and killing ungulates and that minimized their chances of encountering humans. We assessed habitat selection by these predators during summer using within-home range (3rd order) resource selection functions (RSFs) in multiple study areas throughout western Montana, and tested how generalizable RSF predictions were by applying them to out-of-sample telemetry data from separate study areas. Selection for vegetation cover-types varied substantially among wolves in different study areas. Nonetheless, our predictions of 3rd order selection by wolves were highly generalizable across different study areas. Wolves consistently selected simple topography where ungulate prey may be more susceptible to their cursorial hunting mode. Topographic features may serve as better proxies of predation risk by wolves than vegetation cover-types. Predictions of mountain lion distribution were less generalizable. Use of rugged terrain by mountain lions varied across ecosystem-types, likely because mountain lions targeted the habitats of different prey species in each study area. Our findings suggest that features that facilitate the hunting mode of a predator (i.e. simple topography for cursorial predators and hiding cover for stalking predators) may be more generalizable predictors of their habitat selection than features associated with local prey densities.

Consequences of migratory strategy on habitat selection by mule deer

“…Migrants on the Rocky Mountain Front were an exception; they did not avoid mountain lions at the home range scale. In that study area, mountain lions tended to select steeper, more rugged terrain than the other 2 study areas (Peterson et al 2021), which may make them more difficult for mule deer to avoid. Alternatively, seeking refuge from wolves may have exposed Rocky Mountain Front migrants to higher mountain lion risk (Atwood et al 2009), as they were the only group of deer that avoided wolves at the second order.…”

“…Details on RSFs for predators can be found in Peterson et al (2021). Study area‐specific wolf RSFs performed well during internal k‐folds cross validation (Spearman correlations [ r s ] = 0.957–0.967).…”

“…For instance, the wolf RSFs we used approximated the average, population‐level behaviors of wolves throughout summer, and did not account for intra‐season temporal variation in their behavior, which could alter the spatial distribution of predation risk from wolves between early and late summer (Mech and Boitani 2003). Each wolf RSF did perform well in external validation (Peterson et al 2021), justifying their use as general proxies of the relative probability of encountering wolves. The mountain lion RSFs were developed based on data from outside our study system and validated well in the Whitefish Range and Cabinet‐Salish but were not extremely accurate when tested on the Rocky Mountain Front, so they should be considered a coarse proxy of the relative probability of encountering mountain lions in that study area (Peterson et al 2021).…”

“…Each wolf RSF did perform well in external validation (Peterson et al 2021), justifying their use as general proxies of the relative probability of encountering wolves. The mountain lion RSFs were developed based on data from outside our study system and validated well in the Whitefish Range and Cabinet‐Salish but were not extremely accurate when tested on the Rocky Mountain Front, so they should be considered a coarse proxy of the relative probability of encountering mountain lions in that study area (Peterson et al 2021). Further, none of the predator RSFs used included prey density variables as predictors, but RSFs did include habitat features that facilitate cursorial hunting by wolves (e.g., simple topography) or stalking and ambushing by mountain lions (e.g., canopy cover, terrain ruggedness), which have been shown to be more effective than prey density in predicting habitat selection by wolves (Uboni et al 2015) and mountain lions (Coon et al 2020) in some ecosystems.…”

“…Predation risk for ungulates is influenced by the spatial distribution and resource selection of their predators (Moll et al 2017). As indices of predation risk, we used third‐order resource selection functions (RSFs) for predicting the relative probability of selection by wolves and mountain lions in our study areas during summer, which were developed as part of an associated research project (Peterson et al 2021). That study developed an RSF for wolves in each of our study areas using GPS‐collar data from 18 individual wolves among 13 packs: 4 in the Cabinet‐Salish, 6 on the Rocky Mountain Front, and 3 in the Whitefish Range collared from 2015–2018.…”