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A unique tree-climbing fox is on the decline in the Midwest. Researchers want to know why

A gray fox perched on a log. Within the last four years, Iowa, Illinois, Indiana and Ohio have launched gray fox studies to find out why numbers have declined and what may help the species rebound.
Courtesy of the Ohio Division of Wildlife.
A gray fox perched on a log. Within the last four years, Iowa, Illinois, Indiana and Ohio have launched gray fox studies to find out why numbers have declined and what may help the species rebound.

Gray foxes, the only canine species in North America that can climb trees, are found across much of the U.S. But over the last two decades, populations in the Midwest have plummeted and multiple state agencies are trying to find out the reasons behind their shrinking numbers.

On the outskirts of Keokuk, a city in Iowa’s southeastern tip, Dave Hoffman descends into a brushy, wooded ravine to check a trail camera.

It’s mounted low on a tree, pointing straight at a half-buried, four-inch black plastic drainage pipe. This unassuming hole in the forest floor also happens to be one of the den sites of a gray fox — a secretive and exceedingly rare species in the state.

Walking along a cedar thicket, the wildlife technician with the Iowa Department of Natural Resources points out bird droppings and other animal signs.

Dave Hoffman, a wildlife technician with Iowa Department of Natural Resources, adjusts a trail camera near a gray fox den site in Keokuk. He says the camera has captured images of other wildlife, including racoons, coyotes, a red fox and an opossum, and he suspects that they evict the gray fox at times.
Rachel Cramer
/
Harvest Public Media
Dave Hoffman, a wildlife technician with Iowa Department of Natural Resources, adjusts a trail camera near a gray fox den site in Keokuk. He says the camera has captured images of other wildlife, including racoons, coyotes, a red fox and an opossum, and he suspects that they evict the gray fox at times.

“I was seeing lots of feathers here a couple of weeks ago on the snow,” Hoffman said. “This gray fox can climb these trees and actually get some of these birds roosted in some of these trees here.”

Gray foxes are one of the few canines in the world known to climb trees; their rotating forearms and semi-retractable claws help them scoot up trunks to hunt and escape predators. The unique canine can be found throughout nearly all of the U.S., north into the eastern edges of Canada and south through Central America and the northern part of South America.

Yet their numbers have steadily dropped in several Midwestern states. In Iowa, for instance, historic harvest data and wildlife observation surveys conducted by DNR staff and volunteers indicate a steady, downward trend over the last 25 years.

“It’s to the point now that it’s a pretty big concern because the population is so low that we’re at risk of losing this wildlife species out there,” said Vince Evelsizer, an Iowa DNR furbearer biologist. “And on top of that, there really isn’t very much research that has been done about the gray fox in the Midwest.”

Wildlife biologists from Illinois, Indiana and Ohio have noticed a similar decline and are looking for answers. Now researchers at state agencies in all four states are conducting studies, hoping to share what they learn to better understand regional trends.

Leading the way

Indiana was the first of the four states to launch a gray fox study, starting in 2020.

Geriann Albers, Indiana DNR’s furbearer and turkey program leader, said people were noticing fewer gray foxes in certain parts of the state

“We were hearing some concern from the public, especially from licensed trappers, that they weren’t seeing them anymore where they used to, and that spurred us to start looking into and put some funding toward this big research project to find out what was going on,” Albers said.

Indiana partnered with the nonprofit Wildlife Ecology Institute to gather and analyze field data from two multi-county study sites – a highly forested area along the southern border with Kentucky and a more agricultural area farther north.

With the help of local trappers and trail cameras, they captured, radio-collared and released 28 gray foxes, most of which were in the southern site.

A gray fox is captured on camera as it begins to climb a small tree in Indiana in July 2021. With semi-retractable, hooked claws and rotating forearms, the gray fox is one of two species of canid with this ability.
Courtesy of Indiana DNR/Wildlife Ecology Institute
A gray fox is captured on camera as it begins to climb a small tree in Indiana in July 2021. With semi-retractable, hooked claws and rotating forearms, the gray fox is one of two species of canid with this ability.

Dawn Reding, a wildlife geneticist and associate professor of biology at Luther College in Iowa, is leading the lab work. To understand the prevalence of certain diseases, Reding tests blood samples for bacteria and viruses, and antibodies, which indicate the fox’s immune response to recent or past infection. She’s also looking for environmental toxins in the blood, like lead and rodenticides.

By analyzing DNA, Reding is learning more about the gray foxes’ genetic diversity and diet. This includes samples from animals that were killed by vehicles or died over the course of the project.

“When I see a carcass, I see gold,” said Reding. “All the different pieces of information that you can gather from that carcass is amazing in terms of genetic material.”

That information may help researchers determine what’s behind the decline in gray foxes – and address it.

As Indiana's gray fox study wraps up later this year, Albers says the DNR can use the research findings to make recommendations, whether for new regulations or population re-introduction.

“We can evaluate all of those things once we have this data to help us inform those decisions to figure out what tool is the right tool for the job or what suite of tools are the right tools for the job,” she said.

Possible causes of decline

While Iowa, Illinois, Indiana and Ohio have hunting and trapping seasons for gray foxes, it’s unlikely that these activities are the largest threat to the species, at least in Iowa, according to Evelsizer.

The DNR conducted a fur harvester effort survey from 2018 to 2021 with a subset of predator hunters and trappers. Participants kept track of what they caught in a season and what they were targeting.

“Less than 1% of the fur harvesters targeted gray fox. I think the importance of that is that while their numbers are low, we do not feel that trappers are driving their population down,” Evelsizer said.

According to the DNR’s “Trends in Iowa Wildlife Populations and Harvest” logbook, one gray fox was harvested during the 2021-2022 season compared to an all time high of 3,093 during the 1979-1980 season.

A gray fox looks out of a tree hollow. Researchers are working to find out what's causing the decline in numbers across several states in the Midwest.
Courtesy of the Ohio Division of Wildlife
A gray fox looks out of a tree hollow. Researchers are working to find out what's causing the decline in numbers across several states in the Midwest.

Evelsizer says factors that may play a bigger role in the decline of gray foxes are habitat loss, disease and competition with other wildlife. Researchers have documented coyotes and bobcats harassing and killing gray foxes in or near their territories.

While there’s still a lot of data to dig into with the Indiana project, Reding said one of the causes for the decline in gray foxes may be a highly contagious disease.

“Canine distemper virus seems to be a major source of mortality for gray foxes in our study area, and this is important: they’re not the only species that can get canine distemper virus,” said Reding.

Infected coyotes, racoons, skunks and unvaccinated dogs and cats shed the virus through respiratory droplets, saliva, urine and feces. Feeding from the same carcass or pet food bowl, grooming or simply coughing in the vicinity of another animal can quickly spread the disease between individuals and across different species.

The Midwest has a big population of racoons that may be serving as a reservoir of distemper, according to Tim Hiller, the founder and executive director of Wildlife Ecology.

“We have a video of a gray fox den and very close interactions with racoons that were harassing that gray fox,” Hiller said. “So, undoubtedly, the question may be at what level these two species are interacting – not whether they’re interacting.”

A 2022 study from North Carolina State University highlights how tree cover may affect another interspecies interaction.

While gray and red foxes are native to North Carolina, coyotes arrived within the last several decades. The study’s lead author, Arielle Parsons, says the timing offered a unique opportunity to track potential impacts on foxes. Specifically, the researchers wanted to know if coyotes and foxes were using the same habitat and at the same time.

Over 300 trained citizen scientists helped set up camera traps along the urban, suburban and rural gradient around Raleigh. Among the findings, gray foxes in rural areas used the same sites as coyotes, at roughly the same time – if there was enough tree cover. Without it, gray foxes avoided areas that had recently been used by coyotes or shifted to being active later at night.

Parsons said this suggests that gray foxes are climbing trees to temporarily avoid coyotes.

“I do think that what is happening in North Carolina and kind of this result of the tree cover can be extended to the Midwest,” Parsons said.

She sees it as a hypothesis that could help researchers determine what is happening to gray fox populations.

“Because we’re all seeing indications that coyotes are playing a role,” she said, “but clearly habitat is an important factor, and likely there’s an important interaction between the two.”

Volunteers help in Iowa

In Iowa, DNR officials asked for the public’s help to find, and even capture, live gray foxes for its pilot study.

Evelsizer said he’s been “pleasantly surprised at the amount of public support and interest.” People have shared trail camera photos and sightings from around the state.

In November 2023, William Deck caught a gray fox in Lee County, Iowa, for the DNR's pilot study. "I'm probably as shocked as anybody that he was in that trap," said Deck. Deck and DNR biologist DaveHoffman said "gray fox one" or "GF1" was surprisingly docile and calm.
Bill Deck
In November 2023, William Deck caught a gray fox in Lee County, Iowa, for the DNR's pilot study. "I'm probably as shocked as anybody that he was in that trap," Deck said. Deck and DNR wildlife technician Dave Hoffman said "gray fox one" or "GF1" was surprisingly docile and calm.

Then last November, Evelsizer and Hoffman received a call from a trapper near Keokuk who had captured a 10-pound male. They traveled with the state wildlife vet to put a tracking collar on the fox, called GF1, as well as take measurements and a blood sample.

"We released him and he took off and he stayed in the area,” said Hoffman. “He seems to be doing really well.”

Now Hoffman is able to use an antenna and radio receiver to narrow down GF1’s location. Once he’s within range, he can then connect with the gray fox’s GPS collar and download all of the fox’s movement data.

“This will tell us about his den sites and the habitat that he’s using here,” said Hoffman, flipping open a laptop to reveal an aerial map and a web of green lines.

Since Hoffman is based over four hours away from Keokuk, he said he relies on “a small army of volunteers” to help collect data on GF1. One of them, Harry Brackenbury, drives up to Hoffman’s parked truck to discuss GF1’s latest movement data.

Brackenbury checks the fox’s tracking signal several times a day and records weather conditions.

“Being an avid outdoorsmen and hunter myself, it’s not all about the taking of an animal all the time. It’s preservation,” said Brackenbury.

So far, GF1 is the only gray fox the Iowa DNR has caught for the project, but the researchers hope to collar more in the coming years to learn about the canine’s habitat use and range, behaviors, genetic diversity — and what’s behind their decline.

This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest. It reports on food systems, agriculture and rural issues.

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