LISTEN TO THE AUDIO VERSION
The calm during the storm: Snowfall events decrease the movement rates of grey wolves (Canis lupus). Droghini A, Boutin S. PloS one. 2018 Oct
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.
University of Alberta researchers tracked wolf movements during periods of snow
By CBC News
Photo University of Alberta researchers studied the movements of Canadian grey wolves like this one. They found that wolves slowed down and travelled less during snowfalls. (MacNeil Lyons/National Park Service)
When snow falls, wolves chill out, according to a recent study from the University of Alberta.
Over two winters, researchers looked at the movements of grey wolves near Fort McMurray, Alta. in conjunction with data on snowfall in the area.
“We found that on the night that it was snowing, wolves rested more than they travelled, and when they travelled, they travelled slower than on other days when there wasn’t any snowfall,” Amanda Droghini, a former master’s student with the biology department.
The researchers also found that within a day of the snowfall, the wolves returned to their normal movement behaviours. They don’t know exactly why the wolves changed their movements, but they have some theories.
“We think that it might be something about actively falling snow,” said Droghini.
Snow, like rain, clears the air of scent molecules, she said. Wolves rely heavily on their sense of smell to hunt, especially at night. Most of the wolves studied do their hunting after dark.
Another possible explanation, said Droghini, is that the wolves’ prey move less in falling snow.
“We unfortunately don’t have the data to test this,” she said, but if other animals are hunkered down, waiting for the snow to stop, there is no incentive for the wolves to go out hunting.
In their study, researchers used cameras and data transmitted from collars on 17 wolves. (Submitted by Amanda Droghini)
The researchers used data from remote cameras that monitored snowfalls, and collars on 17 wolves. These wolves were also part of a separate study that looked at the movement of wolves and moose near Fort McMurray.
It’s hard to say right now how climate change might affect the behaviour of wolves in snow, said Droghini.
Information about snow conditions is scarce, particularly in the North where there aren’t many weather stations.
Droghini said more freeze and thaw cycles could make movement difficult for animals in winter.
Rain after snow can create an icy crust over the snowpack, and this kind of snow is the most challenging for animals to walk through, she said.
“It costs them a lot of energy.”
The concern, said Droghini, is that it might be more difficult for animals to maintain the energy levels they need for the reproductive season.