VOYAGEURS NATIONAL PARK, Minn. — Human activity has significantly impacted the relationship between predator and prey in northern forests, in some surprising ways.
A study initiated by the Voyageurs Wolf Project has uncovered new information about how humans have changed the wolf-deer relationship by modifying the forest ecosystem.
Results of the research were published Monday in the journal Ecological Applications.
"The premise is really quite simple. Human activities change where deer are on the landscape, and wolves go where the deer are," said Voyageurs Wolf Project leader Thomas Gable, a postdoctoral researcher at the University of Minnesota.
For every notable way that people have altered the forest landscape, including logging, road and trail development, and establishing infrastructure, there has been a consequential effect on where wolves hunt and kill deer fawns.
Some of the key findings of the study include:
- Disproportionately, wolves pursue fawns in areas that have been logged within the past five years, likely because clear-cut forests produce dense stands of saplings which are a good food source for deer while providing hiding spots for newborns. The study team noted that wolves seem to know recently-logged areas are good hunting spots, "turning the nursery grounds into risky areas for deer fawns during summer."
- Wolves tend to kill fawns at a higher-than-expected rate nearer human infrastructure such as residences, barns and cabins. This is believed to be partly the result of people feeding deer, which in turn attracts wolves.
- Wolves prefer to use roads, trails, and power line corridors for hunting fawns, rather than travel through the forest.
In an interview with TBnewswatch, Gable said that until now, there's been little research into the relationship between wolves and deer fawns.
"Finding where wolves kill fawns is quite complex and difficult, because wolves can eat a fawn in a pretty short period time, and leave very little left to actually find in the field."
But he said the team was able to develop ways of searching clusters of areas habituated by collared wolves whose movements are tracked by radio transmissions.
"Once we we started finding where wolves were actually killing fawns, that started getting us interested in the sort of larger patterns, like where are they actually doing this in terms of landscape-level patterns. What's driving where wolves kill fawns?...Interestingly, most of the most important variables from our analysis, or the ones that seem to most influence where wolves killed and hunted fawns, were those human-related factors."
Some of the findings were more surprising than others, Gable said.
"In some sense, I guess it's fairly logical when you think about it. There's a lot of work from in Canada, particularly British Columbia and Alberta, where they have a good understanding that roads and trails and other human-created 'linear features,' basically anything that humans clear to help travel, that wolves like those to move around, and that they often influence wolf predation behaviour. So we were kind of expecting that might play a role, which it did."
He said the team members were intrigued, however, by the role infrastructure plays in predatory behaviour.
"Because, generally speaking, wolves do avoid people, right? They're very good at avoiding people, but we see them coming in and around cabins, residences, barns, that sort of stuff, and that's likely because that's where the deer are hanging out...They probably do a lot of their activities at night when people aren't out. But I think that will be surprising to most people, especially in the resort communities."
Gable commented that when he tells people he's studying wolves, they often reply that they haven't seen a wolf around for a long time, but his response might be "Well, I know they were about 200 metres from your cabin a couple of nights ago."
Although the study makes clear that humans have influenced the wolf-deer relationship, it doesn't determine whether human activities have actually increased the rate of wolf predation.
"Like, we haven't been able to say conclusively that clear-cutting increases predation, or adding these roads and trails increase the number of fawns that wolves kill. All we can conclude right now is that it impacts where wolves make the kill," Gable said.
"There's a lot of work in the wolf/caribou world in Canada that has pretty good data to suggest that when people create roads and trails, and harvest forests, and things like that, that they are actually increasing wolf predation rates on caribou."
The co-lead author of the study is Sean Johnson-Bice, a Ph.D. candidate at the University of Manitoba.
He observed that "it's possible we have created conditions that may have tipped the scales in the predators' favour."
More work is needed to understand whether human activities have actually increased wolves' efficiency at hunting deer.
The study team is currently examining various approaches for answering that question.
Participants in the project include researchers from the University of Minnesota, Northern Michigan University, Voyageurs National Park and the University of Manitoba.
