Three-year study finds white-tailed deer not affected
Mule deer change their behavior, including moving to higher elevations, in areas where they are threatened by wolves, according to a study conducted by University of Washington researchers.
The three-year study of deer herds near Republic, in areas occupied by the Nc’icn and Strawberry gray wolf packs, found that mule deer exposed to wolves spend more time away from roads, at higher elevations and in rockier landscapes. White-tailed deer, however, were found not to change their behavior in areas occupied by wolves.
Mule deer and white-tailed deer, two distinct species common in Washington, are among wolves’ favorite prey. Wolves will chase deer great distances — sometimes upwards of 6 miles — in search of a meal.
As gray wolves continue to make a strong comeback in Washington state, their presence can’t help but impact other animals, particularly those targeted by wolves as prey, the UW study said. Researchers wanted to find out how the two deer species respond to the threat of a growing population of wolves.
“In any particular ecosystem, if you have a predator returning, prey are unlikely to all respond similarly,” said Aaron Wirsing, senior author of the study and an associate professor in the UW School of Environmental and Forest Sciences. “We show that wolves don’t have a uniform effect on different deer species.” Results of the study were published in the journal Oecologia in December.
Wolves were completely wiped out in Washington in the last century, but began returning to the state from Montana, Idaho and Canada about a decade ago. State wildlife officials estimate there are about 200 wolves in packs across eastern Washington today, according to the study.
Both white-tailed and mule deer are important food for gray wolves, but they have different methods of eluding predators. White tailed deer are smaller animals with a distinctive long white tail that stands up when the deer is alarmed. Mule deer are bigger, with large dark ears and a black-tipped tail.
White-tailed deer sprint away from predators and rely on spotting them early enough to try to outrun them. Mule deer “stot,” a quick bound with all four legs touching the ground at the same time. This bounding gait helps them negotiate all types of terrain and gives them an agility advantage over predators in rocky, uneven areas where running is difficult.
Given these known tactics, researchers focused on “flight behavior” of deer living in areas where wolves have returned, and in areas without wolves. The researchers chose four study areas near Republic. All four areas are home to both species of deer, but only two areas were occupied by known wolf packs during the study period.
In partnership with the Confederated Tribes of the Colville Nation and the U.S. Forest Service, researchers set up cameras, captured and put collars on wolves and deer, and monitored data from the collars from 2013‑2016.
Overall, the researchers found that mule deer in gray wolf areas changed their behavior to avoid wolves altogether — mainly by moving to higher, steeper elevations, away from roads and toward brushy, rocky terrain. White-tailed deer were more likely to stick to their normal behavior in wolf areas, relying on sprinting across open, rolling terrain with good visibility, including along roads.
“Mule deer faced with the threat of wolves are really changing their home ranges, on a large scale,” Wirsing said. “They appear to have shifted kilometers away from where they had been prior to the return of wolves, generally going up higher where the terrain is less smooth and where wolves are less likely to hunt successfully.”
These shifts among mule deer could affect hunting opportunities. Some hunters in eastern Washington have reported seeing mule deer higher on ridges where they are less accessible than in past years, Wirsing said. Hunting for white-tailed deer won’t likely change to the same degree, the research suggests.
The Methow Valley is home to two gray wolf packs, the Lookout and Loup Loup packs. But research like the study near Republic has not been conducted in the Methow Valley, so it’s unclear whether deer behavior might be changing here, said Scott Fitkin, a wildlife biologist with the Washington Department of Fish and Wildlife (WDFW) in the Methow Valley.
“We don’t have enough data to answer the question. That said, I’m not sure we have a high enough wolf density at this point to create a noticeable effect,” Fitkin said. The most recent survey of wolf populations by WDFW estimated two wolves in the Loup Loup pack and three in the Lookout pack as of Dec. 31, 2017. A wolf census for 2018 is expected at the end of March.
UW researchers have collared deer, cougars and wolves in the Methow Valley for other research projects on the interrelationship of predators and prey.
“Preliminary data from our collared mule deer suggest they are using the landscape similar to how they have in the past. Perhaps in a few years when all the data from the collars is in the researchers will be able to look for patterns similar to what was seen in the other study,” Fitkin said.
Long-term changes among mule deer in wolf area could affect other parts of the ecosystem, and perhaps reduce the number of deer-vehicle collisions, Wirsing said.
The study of deer behavior was funded by the UW, the National Science Foundation, the Safari Club International Foundation, Conservation Northwest and WDFW.