Yellowstone elk don't budge for wolves

S.J. & Jessie E. Quinney College of Natural Resources, Utah State University

IMAGE: Utah State University researchers and their colleagues have shown that wolves reintroduced to Yellowstone National Park in the mid-1990s have negligible impacts on the movements of adult female elk that... view more 

Credit: Matt Metz

Elk roam the winter range that straddles the northern boundary of Yellowstone National Park with little regard for wolves, according to a new study illustrating how elk can tolerate living in close proximity to the large predator.
The study offers new insight into how wolves can have negligible impacts on elk movements, and how elk may simply ignore the risk of wolf predation while navigating the landscape in search of forage. It also adds to a growing body of evidence that changes in elk distribution and vegetation conditions in northern Yellowstone since wolf reintroduction in the mid-1990s are not caused by wolves altering elk movement behavior.
Utah State University researchers Dan MacNulty and Michel Kohl co-led the study, published in the Journal of Animal Ecology, with Jeremy Cusack (University of Stirling), Tim Coulson (University of Oxford), Matt Metz (University of Montana), Doug Smith and Dan Stahler (Yellowstone National Park). Several organizations funded the research, including the National Science Foundation, Natural Environment Research Council, Yellowstone Forever, The Tapeats Fund, Perkins-Prothro Foundation, and the National Park Service. The Park-led wolf and elk monitoring programs provided data for the project.
The team used global positioning system (GPS) radio-collars to track the movements of elk and wolves across four winters between 2012 and 2016. They tracked 34 adult female elk and at least one member of each dominant wolf pack. The collars recorded the location of the animals every 1-3 hours, providing comprehensive data on how they used the landscape. The team tested if elk avoided wolves that were in close proximity, and if elk avoided 'risky areas' where they might be killed by wolves, including where wolf densities were high; where wolves had previously killed elk; and open grasslands where wolves often hunted.
"We compared recorded elk movements with those from a simulation that described how elk would move if they completely ignored wolves and risky areas" says MacNulty, who has studied wolf-elk interactions in northern Yellowstone since 1995 and is an associate professor in USU's Department of Wildland Resources and Ecology Center. "In 90% of cases, there was no difference between real and simulated elk movements, indicating that our sample of real elk mostly ignored the risk of wolf predation".
According to Cusack, the lead author of the study, most elk did not alter the location and configuration of their annual winter home ranges to minimize overlap with wolves and risky areas, and none bothered to steer around wolves that were in the immediate vicinity. "A few elk avoided open grasslands during daylight hours when wolves were most active, which mirrors the result of a separate recent study that examined finer-scale elk movements in the early 2000s when wolves and elk were more numerous," explained Cusack.
The findings are also in line with other studies of northern Yellowstone elk, including one that compared elk movements before and after wolf reintroduction and found that "in winter, elk did not spatially separate themselves from wolves". Another study reported that "elk did not grossly modify their migration timing, routes, or use areas after wolf restoration".
Why don't elk budge for wolves? "A main reason is that elk tend to be philopatric, which means they have an inherent tendency to habitually return to the same wintering and summering areas year after year," says MacNulty. "Familiarity with an area helps them find the high quality forage they need, and this outweighs the small chance they encounter and fall prey to wolves."
MacNulty and Cusack estimated that elk in their study encountered wolves once every 7 to 11 days, and previous research found that elk frequently survive their encounters with wolves. Low risk of predation was also reflected in relatively high rates of annual survival, particularly among younger adults. "Elk in their prime do not have a massive incentive to avoid wolves, especially in winter when forage is scarce," explains MacNulty.
He says that elk intransigence towards wolves is a reminder that altered movement behavior is not the only way prey species avoid predation.
"Antipredator behaviors during encounters - including fighting back, grouping, and running - are effective ways for large-bodied, philopatric prey like elk to avoid predation without abandoning or reconfiguring their home ranges," he says.
"This has implications for understanding how wolves and other predators, including humans, affect the distribution of philopatric prey like elk. Predators removing different numbers of elk in different areas is the main way they affect elk distribution. Elk movement away from risky areas, if it happens, is secondary."

Coyotes are not controlling deer populations in eastern US states

Coyotes expanded their range to colonize eastern North America over the last century, where their impacts on white-tailed deer populations are highly debated. In a Journal of Wildlife Management study, researchers conducted the first long-term, large scale assessment and documented no consistent decline in deer harvest numbers after coyote arrival.
For the study, the team evaluated deer harvest numbers from 1980 to 2014 in 384 counties of six eastern US states.
The results indicate that coyotes are not limiting deer numbers and that coyote removal programs will do little to increase regional deer numbers.
"Coyotes on the east coast of the United States have not been limiting deer, so eradicating coyotes is not an efficient way to increase deer numbers in the region," said lead author Dr. Eugenia Bragina, of the Wildlife Conservation Society.

Video on this:  

IMAGE: A coyote captured on camera trap preying on a deer fawn. view more 

Credit: Dr. Aimee P. Rockhill (Western Carolina University) and Dr. Christopher S. DePerno (North Carolina State University)

Coyotes eat deer, but not enough to limit the deer population at a large scale. A new study of deer numbers across the eastern United States has found that the arrival and establishment of coyote predators has not caused the number of deer harvested by hunters to decline.
A video presenting this research is available for article embedding or linking here: https://youtu.be/2XCbHhDlU_k
"With wolves and cougars extinct in most of the eastern U.S., white-tailed deer have become abundant, sometimes overabundant," says Roland Kays, wildlife biologist at the North Carolina Museum of Natural Sciences and North Carolina State University, and co-author of a paper describing this research. "Coyotes moved in as the new top predator of the east, but they aren't nearly as effective deer hunters as wolves, so there's been a lot of controversy about whether these medium-sized predators can really limit deer populations at large scales."
Previous studies of how coyotes might be affecting deer populations have produced inconsistent results. Some experimental removals of coyotes found that fawn survival increases following coyote removal, but others have shown no effect. Kays and a team of researchers led by Eugenia Bragina from NC State, surveyed deer population trends from 1981 to 2014 using data from 384 counties across six eastern states. "Our study is unique because it's the first to link coyote presence to changes in deer population at a large scale," Bragina says. "Getting the big-picture of the interactions between these species helps inform the management practices of these species by hunting agencies."
The researchers collected county-by-county data on coyote arrival by assessing museum collections, and deer population numbers by tracking hunting records from state wildlife agencies. They evaluated these data for changes in the number of deer harvested after coyote arrival and establishment in an area, while accounting for environmental differences like climate and landscape. They found that the number of harvested deer in all states generally increased over time, and that there was no consistent crash in harvest numbers following coyote arrival. They concluded that coyotes are not controlling deer populations at a large region-wide scale in the eastern North America.
"We see direct evidence of coyote predation on deer when looking at coyote scat or even spotting them with camera traps carrying off deer fawns," says Chris Deperno, a co-author on the study from NC State. "Though coyotes are known to kill adult deer, predation is focused primarily on vulnerable individuals that are sick, injured or in late stage pregnancy. Predation of healthy adults is uncommon."
The researchers caution that this species interaction could potentially change as coyote numbers are still on the rise across the eastern U.S. It is unknown whether coyote populations will increase in number or density enough to influence deer populations in the future. Human-induced changes in habitat quality or landcover may also influence how these species interact.
Management efforts to increase deer population sizes involving coyote removal, the researchers advised, are unlikely to be effective at large scales or over long periods of time. "Coyote removal as a method of increasing deer abundance is expensive and labor-intensive," Bragina says. "We hope that this research leads to more acceptance of this carnivore by people. Coyotes are here to stay."
The paper, "No region-wide effects on white-tailed deer following eastern coyote colonization," is published in the Journal of Wildlife Management and Wildlife Monographs. Allison Hody, Christopher Moorman and Christopher Deperno from NC State, as well as L. Scott Mills from University of Montana, co-authored the research.

Hungry moose more tolerant of wolves' presence

IMAGE: A GPS-collared moose in western Wyoming moves into its desired habitat. New University of Wyoming research has documented interactions between moose and wolves in the region. view more 

Credit: Mark Gocke

Driven by the need for food, moose in western Wyoming are less likely to change their behavior to avoid wolves as winter progresses, according to new research by University of Wyoming scientists.
The findings, published today (March 13) in the journal Ecology, provide new insights into the interactions of the region's apex predators and their prey. The results also highlight the complexity of the relationships between wolves and big-game species, making it difficult to reach general conclusions about whether and how fear of wolves has impacted the ecosystem, the researchers say.

"We have known for some time that hungry animals will tolerate the presence of predators in order to forage and avoid starvation, and that phenomenon, called the 'starvation-predation hypothesis,' is supported by our research," says Brendan Oates, now with the Idaho Department of Fish and Game, who conducted the research as a UW graduate student. "In this case, close proximity of wolves does cause moose to move, but not enough to drive them from their preferred habitats -- especially late in the winter."

Oates is the lead author of the Ecology paper. Co-authors include his UW advisers: Jake Goheen, associate professor in UW's Department of Zoology and Physiology, and Matt Kauffman, a U.S. Geological Survey researcher based at UW. UW's Jerod Merkle, assistant professor in the Department of Zoology and Physiology, also was involved with the research, as were agency personnel from the National Park Service and U.S. Fish and Wildlife Service.

The scientists tracked movements of dozens of GPS-collared moose and wolves in Grand Teton National Park and the Bridger-Teton National Forest over a five-year period, detecting 120 unique encounters among 25 individual moose and six wolf packs. An encounter was defined as when moose and wolves were within about 1,600 yards of each other.

They found that movements of moose increased in early winter following encounters with wolves, but only when wolves were within about 550 yards. Even then, the moose didn't move from their preferred habitat, which is near streams and marshy areas. Late in the winter, when the moose were presumed to be hungrier, there was no change in the movement rates of the animals in response to wolves in the vicinity.

"The unwillingness of moose to abandon preferred habitats following encounters with wolves adds further support for the starvation-predation hypothesis," the researchers wrote.

In contrast, previous research has shown that elk -- the primary prey of wolves in the region -- will move when wolves approach within about 1,000 yards, even during winter. Elk also move from their preferred habitat to avoid wolves. The difference may be explained simply by the fact that moose are larger than elk and are more likely to stand their ground when approached by wolves, the researchers say.
Additionally, the nature of moose's preferred habitat -- described as "structurally complex" -- means it could serve as both a good food source and a refuge from wolves.

Still, it would be inaccurate to say that the presence of wolves doesn't affect moose movements.
"Although moose may be generally less responsive to predation risk from wolves, our detection of a heightened behavioral response during early winter suggests that anti-predator behavior is dynamic within and among species of ungulates," the researchers concluded.

Disrupting wolf movement may be more effective at protecting caribou

Woodland caribou populations have been dwindling towards local extinction across much of their range and scientists believe that predators, and specifically wolves, are a leading cause of the decline. Wolf populations are thought to have increased and expanded into caribou range due to the expansion of linear features, such as pipelines and roads, resulting from oil, gas and forestry development.
Controversial practices such as wolf culling and building fenced enclosures have been implemented to reduce the encounters between wolves and at-risk woodland caribou in the Canadian Oil Sands.
New research suggests there may be more effective and less invasive strategies to reduce the ability of wolves to encounter caribou. Researchers used motion-triggered cameras to capture photographs of wolves, caribou, and other wildlife species in the Canadian Oil Sands. The study captured more than 500,000 photographs that were used to study the habitat use patterns of the animals and test management strategies aimed at reducing the impacts of the linear developments on caribou.
The results showed that disrupting the ability of wolves to travel on the linear developments can reduce the ability of wolves to access caribou habitat, without building fences or culling wolves.
A paper describing the research is published in the March issue of the Journal of Animal Ecology, a British Ecological Society journal. The paper reveals new methods for using motion-triggered cameras to study animals. In doing so, researchers found that spreading logs, felling trees, or roughing the soil surface of the linear developments can be used as a habitat recovery strategy to disrupt the ability of humans and predators to access the critical habitats of at-risk caribou.
Disrupting the ability of animals to travel on linear developments is different than recovering the habitat. It takes decades for the habitat to recover in these northern caribou ranges and the cost of reclamation is considered prohibitive. However, disrupting travel on these same features can be more easily implemented, scaled-up across ranges, and reduce the predator's ability to encounter caribou immediately.
Jonah Keim, the lead author of the study, and his collaborators, Subhash Lele of the University of Alberta, Philip DeWitt of the Ontario Ministry of Natural Resources & Forestry, Jeremy Fitzpatrick (Edmonton, Alberta), and Noemie Jenni of Matrix Solutions Inc. have been conducting studies in ecology and data science for more than two decades. In 2011, members of the team co-authored a study revealing the abundances, diets and habitat use patterns of caribou, wolves and moose.
The study suggested that removing wolves may have unintended consequences. This January, the team released the results of a second camera study that shows how to reduce the use of caribou habitat by wolves. Surprisingly, they found that moving recreational snowmobiling trails away from caribou habitats may help draw wolves away from caribou - reducing the opportunistic killings of caribou by wolves.
Encounters between wolves and caribou can be managed by reducing wolf populations or by reducing the ability of wolves to access caribou. The research shows that the expansion of linear features has enabled wolves to more readily travel into caribou range and encounter caribou. Disrupting the ease-of-travel on linear features can reverse the impact on wolf-caribou encounters without wolf culling.