The calm during the storm: Snowfall events decrease the movement rates of grey wolves (Canis lupus)

Abstract

Mammalian predators encounter unique hunting challenges during the winter as snow increases the cost of locomotion and influences predator-prey interactions. Winter precipitation may also affect predators’ ability to detect and pursue prey. We investigated the effects of snowfall events on grey wolves (Canis lupus) in a boreal forest ecosystem in northeastern Alberta, Canada. We predicted that wolves would respond to snowfall events by reducing their travel speed and the time they spent travelling. Over the course of two winters, we used remote cameras to identify localized snowfall events and estimate snow depth. We used telemetry data from 17 wolves to calculate travel speed and time spent travelling versus resting. Data were categorized by time of day (night versus day) and time since snowfall events, and analyzed using linear and logistic regression mixed-effects models. We found that wolves were less likely to travel on dates of snowfall events than any date prior to or after an event. Wolves also travelled slower during snowfall events, but only when compared to their travel speed 24 hours before. Effects were most pronounced at night, when movements appeared to be consistent with hunting behavior, and activity levels resumed within 24 hours of a snowfall event. Including snow depth as a variable did not improve model fit. Collectively, our findings suggest that wolves’ response is not driven by increased hunting success or by energetic considerations resulting from increased snow depth. Instead, we propose that wolves reduce their activity levels because precipitation dampens hunting success. Snowfall events may impact wolves’ ability to detect prey and changes in prey behavior could also lead to decreased encounter rates. We encourage scientists to further investigate the effects of short-term weather events on movement rates and predator-prey interactions.

Environmental correlates of activity and energetics in a wide-ranging social carnivore

“…Snow was only present during the first and last few weeks of our study (absent from May 5 until Sept. 15; [79]). The presence and depth of snow can influence both prey movements and their habitat selection [80,81] as well as the energetic costs of wolf movement [82]. Snow can be an impediment to movement in heavier-bodied herbivore prey due to higher foot loading [39,83], yet wolves were also less active and had lower movements during periods of deeper spring snow in the study area (Fig.…”

The Influence of Snow Properties on Speed and Gait Choice in the Svalbard Rock Ptarmigan (Lagopus muta hyperborea)

“…However, if the feet of these species sink to 60% of the brisket height, the energetic costs could span from 111% to 137% of that for a firm substrate, and beyond this point energy costs increase asymptotically ( Mattfeld 1974 ; Parker et al 1984 ; Fancy and White 1987 ). A 100% increase in the energy cost of locomotion has also been reported for coyote-sized dogs moving through 35 cm deep snow ( Droghini and Boutin 2018a )—77% of the chest height of a coyote ( Murray and Boutin 1991 ).…”

“…This contrasts to the only other data that exist for bipedal locomotion; studies of humans ( Heinonen et al 1959 ; Ramaswamy et al 1966 ) show a reduction in \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$U$\end{document} as sinking depth increases. Reductions in self-selected \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$U$\end{document} are observed in other species, albeit quadrupedal mammals, to keep the energetic cost of moving in deep snow acceptable ( Parker et al 1984 ; Fancy and White 1987 ; Crête and Larivière 2003 ; Droghini and Boutin 2018a ). These previous studies also report a positive association between the cost of locomotion and \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{upgreek} \usepackage{mathrsfs} \setlength{\oddsidemargin}{-69pt} \begin{document} }{}$\bar{D}$\end{document} .…”

Examining the accuracy of trackways for predicting gait selection and speed of locomotion

“…Our ptarmigan studies also highlighted the importance of understanding the influence substrate can have on locomotion [1]. Studies in extant animals have demonstrated that substrate can influence the neuromuscular control of locomotion to maintain stability [43][44][45] and can affect the energetic cost [46,47] and the speed [48] of locomotion. Furthermore, despite the obvious links between trackways and the ground, substrate is rarely considered when inferences into speed and gait are made from tracks.…”