Return of the wolves: How deer escape tactics help save their lives

IMAGE: An adult gray wolf is caught on a wildlife camera in eastern Washington in 2015. view more 

Credit: University of Washington

As gray wolves continue to make a strong comeback in Washington state, their presence can't help but impact other animals -- particularly the ones these large carnivores target as prey.
White-tailed deer and mule deer, two distinct species common in Washington, are among wolves' favorite catch. Wolves will chase deer great distances -- sometimes upwards of 6 miles (10 kilometers) -- in search of a satisfying meal. How these two deer species respond to the threat of being pursued by wolves in the early years of this predator's return could shed light on changes to their behavior and numbers.
To help answer this question, researchers from the University of Washington and other institutions monitored the behavior and activity of wolves and deer in Washington for three years. They found that mule deer exposed to wolves, in particular, are changing their behavior to spend more time away from roads, at higher elevations and in rockier landscapes.
"In any particular ecosystem, if you have a predator returning, prey are unlikely to all respond similarly," said senior author Aaron Wirsing, 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."
Their results were published Dec. 11 in the journal Oecologia.
Wolves were completely wiped out from Washington early last century, but began returning to the state from Idaho, Montana and Canada about a decade ago. The latest estimates now show about 200 wolves in packs across eastern Washington.
Both white-tailed and mule deer are important food for gray wolves. While they might look similar to an untrained eye, white-tailed deer and mule deer are very different animals: Mule deer are bigger, with large, dark ears and a black-tipped tail. White-tailed deer are smaller animals, boasting an unmistakably long tail with a white underside that stands straight up when alarmed.
Aside from their physical characteristics, the two species differ in how they escape from predators. When chased, 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 can give them an agility advantage over predators in rocky, uneven areas where it might be hard to run.
By contrast, white-tailed deer sprint away from predators and rely on spotting them early enough to try to outrun them.
Keeping these known escape tactics in mind, the research team focused on the "flight behavior" of deer living in areas where wolves have returned and in areas without wolves. The researchers chose four distinct study areas, all near the small town of Republic, Washington. All four areas are home to both species of deer, but only two were occupied by known wolf packs at the time of the investigation.
In partnership with the Colville Tribes and the U.S. Forest Service, researchers set up wildlife cameras, captured and put collars on wolves and deer, and monitored the data from all of the collars over three years, from 2013 to 2016. This endeavor involved complex coordination and a dedicated team of UW students who were always ready to respond should an animal enter one of the traps.
"That part of eastern Washington is really special," said lead author Justin Dellinger, who completed the work as a UW doctoral student and now works at the California Department of Fish and Wildlife. "There is huge diversity of large mammals, including all of the native prey populations like big horn sheep, moose and deer. And now we're starting to see a full complement of native predators, like wolves, here as well."
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. Alternately, white-tailed deer that favor sprinting and early detection as ways to escape from predators were more likely to stick to their normal behavior in wolf areas, sprinting across open, gently 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 larger shifts among mule deer could affect hunting opportunities. Indeed, some hunters in eastern Washington have already reported seeing mule deer higher on ridges where they are less accessible than in past years, Wirsing said. Hunting for white-tailed deer likely won't change to the same degree with the presence of wolves, the results suggest.
Long term, changes among mule deer in wolf areas could affect other parts of the ecosystem, and perhaps reduce the number of deer-vehicle collisions. These possible impacts are tantalizing fodder for future studies, Wirsing added.

Wild carnivores stage a comeback in Britain

Once-endangered carnivorous mammals such as otters, polecats and pine martens have staged a remarkable comeback in Britain in recent decades, a new review shows.
The study found that - with the exception of wildcats - the status of Britain's native mammalian carnivores (badger, fox, otter, pine marten, polecat, stoat and weasel) has "markedly improved" since the 1960s.
The species have largely "done it for themselves" - recovering once harmful human activities had been stopped or reduced, according to scientists from the University of Exeter, Vincent Wildlife Trust, the Centre for Ecology and Hydrology and Scottish Natural Heritage.
Hunting, trapping, control by gamekeepers, use of toxic chemicals and destruction of habitats contributed to the decline of most predatory mammals in the 19th and early 20th Centuries.
"Unlike most carnivores across the world, which are declining rapidly, British carnivores declined to their low points decades ago and are now bouncing back," said lead author Katie Sainsbury, a PhD researcher at the Environment and Sustainability Institute at the University of Exeter's Penryn Campus in Cornwall.
"Carnivores have recovered in a way that would have seemed incredibly unlikely in the 1970s, when extinction of some species looked like a real possibility."
The researchers collected survey reports from the last 40 years and compared changes in the species' distribution extent and population sizes. They also reviewed human activities that have helped or hindered Britain's native carnivores in recent decades.
Otters have almost completely recolonised Great Britain. Badger populations have roughly doubled since the 1980s.
Polecats have expanded across southern Britain from Wales, and pine martens have expanded from the Scottish Highlands.
Fox numbers have risen since the 1960s, though an apparent decline in the last decade may be linked with dwindling rabbit numbers.
"Most of these animals declined in the 19th Century, but they are coming back as a result of legal protection, conservation, removal of pollutants and restoration of habitats," said Professor Robbie McDonald, head of Exeter's Wildlife Science group.
"The recovery of predatory mammals in Britain shows what happens when you reduce the threats that animals face. For the most part these species have recovered by themselves."
"Reintroductions have also played a part. Fifty one pine martens were recently translocated to Wales from Scotland and these martens are now breeding successfully in Wales. Otter reintroductions helped re-establish the species in the east of England."
Thought must now be given to how growing numbers of these animals interact with humans, the researchers say.
Some of the species can pose problems for gamekeepers, anglers and farmers, and work must be done to find ways to prevent conflict and allow long-term co-existence as the species expand their ranges and numbers.
Wildcats are the exception to the pattern of recovery. The species is now restricted to small numbers in isolated parts of the Scottish Highlands. Some estimates suggest there are as few as 200 individuals left. Their decline has largely been caused by inter-breeding with domestic cats, leading to loss of wildcat genes.
The status of stoats and weasels remains obscure.
Professor McDonald said: "These small and fast-moving predators are hard to see and to survey. Ironically, the best means of monitoring them is from the records of gamekeepers who trap them. People are key to carnivore recovery.
"By involving local communities from the outset, we have been able to secure the return of healthy numbers of pine martens to Wales. Translocations were needed because natural spread, something the Trust has been monitoring in polecats over the past 25 years, will take much longer for the slower breeding pine marten" said Dr Jenny MacPherson of Vincent Wildlife Trust.
The paper, published in the journal Mammal Review, is entitled: "Recent history, current status, conservation and management of native mammalian carnivores in Great Britain."

Indigenous hunters have positive impacts on food webs in desert Australia

Penn State

IMAGE: This is a drawing of Banded-hare wallabies from John Gould Mammals of Australia, 1845-63. view more 

Credit: Public Domain

Australia has the highest rate of mammal extinction in the world. Resettlement of indigenous communities resulted in the spread of invasive species, the absence of human-set fires, and a general cascade in the interconnected food web that led to the largest mammalian extinction event ever recorded. In this case, the absence of direct human activity on the landscape may be the cause of the extinctions, according to a Penn State anthropologist.
"I was motivated by the mystery that has occurred in the last 50 years in Australia," said Rebecca Bliege Bird, professor of anthropology, Penn State. "The extinction of small-bodied mammals does not follow the same pattern we usually see with people changing the landscape and animals disappearing."
Australia's Western Desert, where Bird and her team work, is the homeland of the Martu, the traditional owners of a large region of the Little and Great Sandy Desert. During the mid-20th century, many Martu groups were first contacted in the process of establishing a missile testing range and resettled in missions and pastoral stations beyond their desert home. During their hiatus from the land, many native animals went extinct.
In the 1980s, many families returned to the desert to reestablish their land rights. They returned to livelihoods centered around hunting and gathering. Today, in a hybrid economy of commercial and customary resources, many Martu continue their traditional subsistence and burning practices in support of cultural commitments to their country.
Twenty-eight Australian endemic land mammal species have become extinct since European settlement. Local extinctions of mammals include the burrowing bettong and the banded hare wallaby, both of which were ubiquitous in the desert before the indigenous exodus, Bird told attendees at the 2019 annual meeting of the American Association for the Advancement of Science today (Feb. 17) in Washington, D.C.
"During the pre-1950, pre-contact period, Martu had more generalized diets than any animal species in the region," said Bird. "When people returned, they were still the most generalized, but many plant and animal species were dropped from the diet."
She also notes that prior to European settlement, the dingo, a native Australian dog, was part of Martu life. The patchy landscape created by Martu hunting fires may have been important for dingo survival. Without people, the dingo did not flourish and could not exclude populations of smaller invasive predators -- cats and foxes-- that threatened to consume all the native wildlife.
Bird and her team looked at the food webs -- interactions of who eats what and who feeds whom, including humans -- for the pre-contact and for the post-evacuation years. Comparisons of these webs show that the absence of indigenous hunters in the web makes it easier for invasive species to infiltrate the area and for some native animals to become endangered or extinct. This is most likely linked to the importance of traditional landscape burning practices, said Bird.
Indigenous Australians in the arid center of the continent often use fire to facilitate their hunting success. Much of Australia's arid center is dominated by a hummock grass called spinifex.
In areas where Martu hunt more actively, hunting fires increase the patchiness of vegetation at different stages of regrowth, and buffer the spread of wildfires. Spinifex grasslands where Martu do not often hunt, exhibit a fire regime with much larger fires. Under an indigenous fire regime, the patchiness of the landscape boosts populations of native species such as dingo, monitor lizard and kangaroo, even after accounting for mortality due to hunting.
"The absence of humans creates big holes in the network," said Bird. "Invading becomes easier for invasive species and it becomes easier for them to cause extinctions." The National Science Foundation and the Max Planck Institute for Evolutionary Anthropology supported this work.