Deer not always to blame for suppressing tree growth

March 20, 2023 by Dana Kobilinsky

Phillip Jones stands in a gap where trees were removed to allow more light to reach the forest floor.

After Wisconsin’s deer population numbers got out of hand in the 1990s, many considered deer the prime suspects for changing the composition of the forests. That raised questions about deer management, since foresters depended on natural forest regeneration for trees of high value and biologists wanted to make sure white-tailed deer (Odocoileus virginianus) weren’t harming the ecosystem.

“There’s been a whole move to find out what is the balance and what is an appropriate density of deer in these different areas, so we could live with the deer and also have the forests we desire,” said Phillip Jones, who was a postdoctoral researcher at Penn State at the time of the research.

“Deer are considered a keystone species, and their presence in large densities influences the structure of the forest, like whether you have enough shrubs for nesting bird species,” he said.

Jones led a study published in Forest Ecology and Management to see how much deer herbivory was impacting seedling growth and survival of two tree species—sugar maples (Acer saccharum) and ash (Fraxinus spp.).

“We expected there to be a strong, measurable effect,” Jones said.

But that wasn’t what they found.

To conduct the study, Jones and his colleagues created an experiment in the Flambeau River State Forest in Wisconsin designed to encourage old-growth characteristics. In 2007, trees had been removed to create three different sizes of canopy gaps, and deer fences were put up to exclude deer in certain areas.

Seedlings that are repeatedly browsed by deer grow into shorter, stubbier seedlings, like this heavily browsed maple. Credit: Phillip Jones/Penn State

“We spent a lot of time trying to find good data on tree seedling survival and growth rates,” said Autumn Sabo, an assistant professor at Penn State Beaver and a co-author on the study.

The team used allometrics—comparing the size of the base of the seedling to its height—to account for deer damage. Determining the role deer played could be pretty complex, they discovered, but there didn’t seem to be much blame to place on deer.

“It was what we didn’t find that surprised us,” Jones said. “We didn’t find a lot of impact from deer.”

Areas that weren’t fenced did show more evidence of deer browsing, but that declined over time. What seemed to give seedlings of both species a higher chance of survival was being in transition zones between gaps and dense canopy.

“Raising seedlings is a complex process, and many things can affect it,” Jones said. “You’ve got soil, competition, light issues—and you’ve got deer.” Jones said there were also species-specific issues that determined if seedlings survived.

“There wasn’t a single magic bullet to give them more light or soil nutrients or just take care of the deer,” he said.

Forests elsewhere might show different results, the researchers said, but Sabo is finding similarly complex patterns on a study in central Pennsylvania.

“The biggest management implication is simply that there are so many different factors that can be influencing the seedling community,” Jones said. “Deer can at times be an overriding factor, but that’s not always the case. When it isn’t, there are other things we need to look into.”

‘There is still a long way to go’

March 20, 2023 by The Wildlife Society

Field Inclusive

“As a master’s student and forestry researcher, I can say from firsthand experience that spending time in nature is one of the most rewarding aspects of doing environmental field work,” writes North Carolina State University researcher Kayla Stukes. “Not only do those of us who work professionally outdoors find peace and joy in what we do, we are, in a way, protectors of the Earth. From wildlife biologists to foresters, we work to protect what we love.

“As a Black woman, however, I’ve learned that the duty of conserving and protecting our planet isn’t always as easy for people like me as it is for others. Often, people from underrepresented racial, religious, and gender groups and other marginalized communities have been made to feel unwelcome in natural spaces, where they should feel safe, secure, and at peace.”

Stukes is an intern with Field Inclusive, a nonprofit founded by TWS members Murry Burgess and Lauren Pharr that seeks to raise awareness for a more inclusive outdoors

In an opinion piece in Undark, Stukes discusses the challenges that researchers from nontraditional backgrounds can face in the field from community members and law enforcement. The issues likely stem in part from the lack of diversity in the career field, she writes.

“As of late, the field has become more inclusive in most aspects, but there is still a long way to go,” Stukes says.

Read more from Undark here.

TWS2022: Do cougars use artificial water sources to ambush prey?

March 17, 2023 by Joshua Rapp Learn

A big juniper tree sat about 15 feet from the artificial water source that the doe and its fawn approached to get a drink. The next moment happened in a flash—a cougar burst forward from behind the cover, chasing away the mother and standing above the fawn, which sat down calmly as if accepting its fate.

TWS member Hunter Prude, a wildlife biologist at Ted Turner’s Armendaris Ranch, and his colleagues wondered whether this kind of activity was happening often—were cougars (Puma concolor) explicitly using drinking stations to capture easy meals?

It appears not, according to research Prude presented at The Wildlife Society’s 2022 Annual Conference in Spokane. Or at least cougars aren’t using these drinking stations directly.

“It wasn’t water sources alone that explained kill sources,” he said.

A cougar encounters a bighorn sheep. Credit: Hunter Prude

From 2007 to 2018, the researchers collared 82 cougars in different study areas in New Mexico and Arizona. After collecting and analyzing data on the patterns of 1,556 ungulate kills, they found that while cougars did prey on some mule deer (Odocoileus hemionus) next to artificial water sources, these incidences were rare. They seemed to occur opportunistically, in cases where cougars were perhaps already at the water source when an unlucky mule deer showed up for a drink.

Just the same, kill sites were roughly related to water sources. The majority of kills did happen relatively close to water sources, though not explicitly at them—in a space from 500-2,500 meters away from the water sources.

Prude, who conducted this work as part of his master’s research at New Mexico State University, said this is likely because mule deer populations are more concentrated around water sources. Cougars prey primarily on mule deer in this region, so it makes sense that they would also hunt more often in these areas of higher mule deer density.

But that doesn’t mean they are explicitly using water sources as places to ambush mule deer, other than opportunistically, he said.

A cougar chews on a bighorn sheep carcass. Credit: Hunter Prude

In the case of the one artificial water source near the juniper tree described above, several instances of predation did occur. But that may have more to do with the placement of the juniper tree near the drinking station. Water sources may also make it difficult for prey to escape. In one case captured on the camera, a mule deer fawn smacked against the converted roof catchment when trying to escape. Sometimes the design of these structures may favor a predator by helping them to corner prey like this. If the structure was built slightly differently, that obstacle wouldn’t have blocked it.

Researchers are concerned that cougars may be using artificial drinking stations to ambush endangered bighorn sheep. Credit: Hunter Prude

Mule deer aren’t exactly in any kind of conservation danger in this area. But desert bighorn sheep (Ovis canadensis nelsoni), considered endangered by the U.S. Fish and Wildlife Service, also use artificial drinking stations. Since cougars sometimes prey on bighorn sheep, wildlife managers looking to boost their numbers may consider placing drinking stations in areas without ambush-worthy cover, Prude said.

Culling vampire bats may exacerbate rabies spread

March 17, 2023 by The Wildlife Society

Culling vampire bats in Peru to stop the spread of rabies may be counterproductive. Latin American countries have been culling common vampire bats (Desmodus rotundus) for decades to control the spread of rabies to cattle, often using rodenticides. In a study published in Science Advances, researchers looked at how effective culling efforts were on bat populations in Peru. They then examined rabies genomes to see how the disease was spreading in the area. The analysis showed that culling bats may actually increase the spread of the virus—bats that weren’t killed but that may be infected fly farther away, taking rabies to new hosts in other areas. In areas without rabies outbreaks, culling might actually help. One alternative to culling bats is to vaccinate more cattle against rabies.

Read more at Popular Science.

Searching new terrain for an endangered alpine fox

March 16, 2023 by Dana Kobilinsky

Researchers are on their way to learning more about an endangered bushy subspecies of red fox that lives in small, isolated populations in the mountains of California and western Oregon.

There are two population segments of the Sierra Nevada red fox (Vulpes vulpes necator) —the Southern Cascades Distinct Population Segment in Oregon and northern California, and the Sierra Nevada Distinct Population Segment in California. The Sierra Nevada population was listed as federally endangered in 2021 when biologists estimated its population had dipped to only about 40 individuals. Since then, researchers continue to learn more about the subspecies in Oregon, but with so few Sierra Nevada red foxes actually in the Sierra Nevada, it’s difficult to collect data on the population there, like where the foxes live, how many there are and how they’re faring.

“Because of the listing, we were now eligible for Section 6 funding from the Fish and Wildlife Service that’s specifically for listed species or species that are potentially going to be listed and are candidate species,” said Chris Stermer, the montane carnivore conservation coordinator with the California Department of Fish and Wildlife.

As a result, the department—joined by partners including the Wildlife Ecology Institute, Sequoia and Kings Canyon National Park and the U.S. Fish and Wildlife Service—received a federal grant to learn more about the species in California. Biologists in Oregon also plan to share their knowledge from research on the foxes that has been done there.

By combining what they continue to learn about the species in both Oregon and California, biologists can “have a greater overall impact for recovery,” said Tim Hiller, executive director at the Wildlife Ecology Institute.

In 2010, biologists conducting surveys on marten (Martes americana) discovered the foxes along the Sonora Pass in the Sierra Nevada of California north of Yosemite National Park. Since then, maps have identified where the foxes have been found throughout Yosemite. The researchers now plan to model potential habitats in the Sierras, in search of areas where additional surveys might turn up the animals. That includes parts of Sequoia and Kings Canyon National Park and areas north of Sonora Pass.

Using the models, the researchers plan to use camera trap stations in places where the fox hasn’t been surveyed. “A lot of remote, backcountry work will be needed to get the cameras back where we want them,” Stermer said.

A Sierra Nevada red fox possibly located a small rodent as prey in the Sonora Pass region of California. Credit: Chris Stermer/California Department of Fish and Wildlife

They will also collect scat and hair samples at bait stations to confirm they’re dealing with the target species and not something like Rocky Mountain red foxes (Vulpes vulpes macroura), another subspecies found in the region.

Hair samples can also tell them more about the population’s genetic diversity, whether individuals are males or females and other important information. They are also seeking additional funding to also allow them to use detection dogs to find red fox scat. This research could also uncover dispersal patterns between red foxes and if there has been any interbreeding between subspecies.

“The short-term goal is to determine whether Sierra Nevada red foxes are present in unsurveyed areas,” Hiller said. Then, he said, there may be a decision to make regarding translocating individuals for either reintroduction or population augmentation and to preserve the genetic makeup of the Sierra Nevada red fox.

That kind of work is already occurring in Lassen Volcanic National Park in northeast California, Stermer said, but for more dire reasons. The population there has low genetic diversity and is inbred. “We are still discovering the status of the Sierra Nevada population, but the Lassen population is in big trouble.”

Plastic ingestion leads to disease in seabirds

March 16, 2023 by The Wildlife Society

Researchers have described a new disease in seabirds connected to the ingestion of too much plastic. Plasticosis can affect birds of any age, including baby chicks that often feed on the regurgitated food from their parents. The disease, which scientists described after studying flesh-footed shearwaters (Puffinus carneipes) in Australia, causes scarring in the digestive tracts. The scarring can cause tubular glands to break down in the upper parts of the digestive tract, which can affect their digestion and make them more vulnerable to diseases. Over time, plasticosis can affect survival and growth of birds.

Read more in The Guardian.

WSB: Spray can help keep the polar bears away

March 15, 2023 by Joshua Rapp Learn

It may not seem likely that spraying noxious liquid will stop a one-ton polar bear from attacking a person. But research shows that it works 95% of the time.

Many northern people are resistant to using bear spray due to the perception that it doesn’t work against such large predators. But Tom Smith has been studying bear spray and advocating for its use in self-defense for some time—both as a means to save people and as a better alternative to shooting the animals. A wildlife science professor at Brigham Young University, Smith knows how it feels to be sprayed—during various experiments evaluating its efficacy, he has sprayed himself and his colleagues a number of times. “It’s a terrible chemical—it’s debilitating,” he said—even as it burns your eyes, mouth and nose, you can’t wash it off, or it feels worse.

That research revealed that cans of bear spray can work in cold temperatures and with strong winds—especially when the bear is close enough. In a study published recently in the Wildlife Society Bulletin, he and his colleagues compiled all the cases they could find where someone actually used the tool against a polar bear (Ursus maritimus) to evaluate its efficacy during real encounters.

A dummy bear on wheels charges toward researchers as they practice spraying it. Credit: Tom Smith

They found 19 cases of people using bear spray to deter polar bears from 1986 to 2019. Six of these were in Russia, 10 in Canada and three in Alaska.

Of those 19 cases, Smith and his colleagues found the spray worked to deter bears 18 times—or in 95% of the cases. “It works on polar bears just the same as grizzlies and black ,” Smith said. “It’s pretty dang effective.”

In the one case that didn’t work, luckily the bear wasn’t attacking someone. The person tried to use the spray to deter the polar bear from rummaging through some gear on a beach, Smith said. But the bear was quite far away and there was a decent amount of wind.

Polar bears weigh between 700 and 1,000 pounds. Like their smaller cousins, black bears (Ursus americanus), they will sometimes approach humans, leading some to characterize them “menacingly curious,” Smith said.

Spraying works not only because of the noxious effects it has on the eyes, nose and mouth. The whole process of shaking the can, the hiss of spraying, and an approaching cloud of aerosols can quickly make a bear shift its priority from curiosity to “get me out of here,” Smith said. “The cloud never even makes it to the animal, but the whole visual and auditory effect frightens them off.”

Bear spray deterred polar bears 95% of the time, according to records. Credit: Tom Smith

It might seem cruel in a sense to spray bears with noxious chemicals, but Smith stresses that it’s a much better outcome than the alternatives that could result in a human or a bear getting killed or injured. “Minimizing conflict is really important,” he said.

Smith added that spray is likely more effective than guns as a deterrent, since it’s easier to use and takes less training. The stress of the situation could also make it harder for humans to operate guns well, he added.

The researchers also examined cases where people had been killed by polar bear attacks in the last 35 years and found that in 93% of those cases, the person may still be alive if they had used a $35 can of spray.

This article features research that was published in a TWS peer-reviewed journal. Individual online access to all TWS journal articles is a benefit of membership. Join TWS now to read the latest in wildlife research.

On a global scale, livestock outweighs wildlife—literally

March 15, 2023 by The Wildlife Society

If you weigh all of the animals in the world, you’ll find that livestock vastly surpasses the biomass of all of the warm-blooded wild animals. Researchers recently found livestock biomass has reached about 630 million tons. That is 30 times the biomass of wild terrestrial mammals and 15 times that of wild marine mammals. “This study is an attempt to see the bigger picture,” said Ron Milo, head of the Mary and Tom Beck Canadian Center for Alternative Energy Research, in a press release. “The dazzling diversity of various mammal species may obscure the dramatic changes affecting our planet. But the global distribution of biomass reveals quantifiable evidence of a reality that can be difficult to grasp otherwise: It lays bare the dominance of humanity and its livestock over the far smaller populations of remaining wild mammals.” To conduct the research, Milo and his colleagues collected existing data on wild mammal species. For ones that didn’t have accessible data, they used machine learning to determine body weight. Among wildlife, they found that species like white-tailed deer (Odocoileus virginianus) and wild boar (Sus scrofa) ranked high on the biomass chart, due in part to human activity.

Read more in Proceedings of the National Academy of Sciences.

North American conference to tackle timely issues

March 14, 2023 by Dana Kobilinsky

88th North American Wildlife and Natural Resources Conference

This year’s North American Wildlife and Natural Resources Conference will provide a platform to discuss contemporary issues including the Endangered Species Act’s successes and challenges, next steps for Recovering America’s Wildlife Act, the North American Model of Conservation and more.

This will be the 88th North American Conference hosted by the Wildlife Management Institute as an annual forum to connect scientists, managers and other conservation leaders to focus on issues like policy, budget and multiregional conservation issues. It will take place March 19 through March 24 in St. Louis, Missouri.

“There’s an interesting history—TWS originally convened its annual business and technical sessions at the North American,” said Matt Dunfee, WMI’s Director of Special Programs and Chair of the North American. The Wildlife Society eventually broke away and created its own annual conference in 1994.

Dunfee, who has been actively involved in both organizations, has worked at the North American Wildlife and Natural Resource Conference since he was a college student getting his degree in fisheries and wildlife conservation at Colorado State University. As part of a program for perspective wildlifers involved in management, Dunfee was invited to work at the conference as WMI staff. He’d go from room to room and make sure there was enough chairs, check the audio and video systems and ensure the conference ran smoothly.

“That was the great unveiling for me as a young professional,” Dunfee said. “I had envisioned myself in snowshoes chasing wolverines. Then, I saw at this conference just how conservation advances in the world and the decisions are made. I always found interesting natural science problems delicious to study, but I think I will always prefer to influence what happens to the science when it goes up the chain.” He has chaired the North American since 2008.

This year’s conference, like past ones, will address current events. “Every year, this conference takes its direction and tone from the challenges and opportunities that exist in a given year,” he said.

One topic will be the 50th anniversary of the ESA, which will be covered through a plenary and then a two-hour session devoted to what we’ve learned, where we need to go and threats to the good work it has led to.

The Wildlife Management Institute has also been working with the Association of Fish and Wildlife Agencies (AFWA) to host and synthesize a national discussion about the North American Model of Conservation. Organizers hope to dive into the critiques of the model by getting audience members to participate in the dialogue in a two-hour session.

Plenary speakers will also address the Recovering America’s Wildlife Act, a major piece of legislation to fund wildlife conservation that failed to pass in the last congressional session. “We push speakers to be honest and not hyperbolic,” Dunfee said. “They’ll say what needs to be said in the way it needs to be said, consequences be darned.”

The Wildlife Management Institute will also welcome former Nevada Department of Wildlife Director Tony Wasley into his new position as WMI’s incoming director.

Each conference, Dunfee said, he hopes participants can make an impact on the ground.

“At too many conferences, we spend too much time promoting ourselves and the work that we been done,” he said. “We spend very little time on how we can reduce ourselves but elevate the resource. At this meeting, we turn away from advocating for ourselves or our missions and turn toward finding solutions through compromise.”

Avian flu challenges bald eagle comeback

March 14, 2023 by The Wildlife Society

Bald eagle

While bald eagle conservation has allowed the large raptors to thrive after near extinction from chemical exposure in the 1960s, they are now facing another challenge—avian influenza. In April 2022, researchers found 660 cases of the H5N1 virus that causes avian influenza in wild birds. At this time, three bald eagles (Haliaeetus leucocephalus) in Georgia died from the virus. Researchers wondered how influenza virus was affecting bald eagle nest success. They found that in coastal Georgia, less than half of the nests fledged one eaglet that year. In a Florida county, nesting success rates were also halved. The researchers said that living in coastal areas puts the eagles at greater risk of catching the virus since it can persist in the water for more than a year. Eagles then catch the virus when consuming infected birds.

Read the study in Scientific Reports.