A new study by researchers from Trent University and University of Alberta (U of A) has uncovered an important insight about a key factor influencing predation risk of snowshoe hares by Canada lynx.

“Predators kill prey. While this simple interaction is ubiquitous in nature, there are many questions that biologists don’t understand, like why one animal was killed and another wasn’t, or why something dies at the precise time and not some other time in its life,” said Dr. Dennis Murray, Canada Research Chair in Integrative Wildlife Conservation at Trent University and one of the study’s collaborators. “One commonly believed mechanism for death is that prey must be active in order to be caught by a predator.”

That mechanism for death is now being contradicted by the research team’s paper published in Proceedings of the Royal Society B which found that periods of low activity for snowshoe hares had little effect on reducing their risk of predation lynx.

Surprising Results

Analyzing data from activity collars (similar to a Fitbit) attached to snowshoe hares and their main predator, Canada lynx, the researchers found that hares are active at night and tend to sit tight during the day, whereas lynx are equally active night or day in winter.

However, to the ecologists’ surprise, hares were as likely to be killed during daytime hours when they were not moving as at night when they were busy foraging. Lynx activity was necessary for kills but prey activity mostly was irrelevant.

“We often assume that prey activity is required for a predator to catch them. For example a mouse can only be caught by you or your pet cat when it is active and running around the house outside of the walls. Turns out this isn’t universally true,” said Dr. Emily Studd, one of the study’s collaborators from the University of Alberta. “For many species, activity may not be necessary at all for them to be killed. Snowshoe hares are one of these species. They are just as likely to be hunted while they sleep as when they are moving around looking for food.”

A Novel Approach to Monitoring Predator-Prey Activity

In order to test whether activity is necessary and predictive of death, researchers needed to know when kills occur and what the prey and predators were doing. Essentially: what time of day do predators kill their prey?

“The answer to this simple question has eluded researchers because it is not easy to determine the exact timing of death in natural ecosystems,” said Dr. Stan Boutin (U of A). “Measuring exactly when wild animals die is incredibly difficult to do.”

Until recently, the best methods could only give scientists the day or week of death. The activity allowed determination of when both species were active throughout the day along with the precise timing of when hares were killed.

This study is one of the first to document the precise timing of death in the wild using a unique and substantial dataset (>1900 naturally occurring kills).

A New Perspective on Predator-Prey Relationships

This study changes how we think about predator-prey interactions and what causes a predator to capture a prey. It also alters our understanding of what activity represents for an animal.

As more and more ecologists are beginning to interpret patterns in activity for conservation and wildlife management decisions, this study comes at an important time.

“Potential risk of activity and foraging has been underlying key predator-prey theories such as the starvation-predation trade-off and the fear effect,” said Shotaro Shiratsuru, one of the graduate students from U of A contributing to the research. “Our findings highlight the fact that the real world is more complicated and thus ecologists need to examine how predator-prey behavioural interactions drive the risk of predation more carefully and thoroughly by taking advantage of cutting-edge biologging technologies.”

Also working on the study alongside Professor Murray from Trent University is Rachael Derbyshire, an Environmental & Life Sciences Ph.D. student.

Read the full paper published in Proceedings of the Royal Society B.

Learn more about Canada Research Chairs at Trent University.