Tree cover helps gray foxes coexist with coyotes in the country

As coyotes have spread outside their native range into the eastern United States, they’ve been known to harass and kill North Carolina’s two native species of fox. A new study finds that preserving tree cover may be essential in helping the gray fox survive with coyotes in rural areas, probably because of the fox’s unusual ability to climb trees.

In the study, researchers used camera traps to find out where gray foxes coexist with coyotes in suburban, rural or wild areas of North Carolina. Surprisingly, they found gray foxes can coexist with coyotes in suburban forest fragments. However, in rural zones, they avoid areas where coyotes live that lack adequate tree cover.

“Coyotes are well known to persecute smaller foxes,” said study co-author Roland Kays, research associate professor at North Carolina State University and director of the NC Museum of Natural Sciences Biodiversity & Earth Observation Lab. “They go out of their way, more than you see in other interactions between species, to really bully, chase and kill the smaller foxes. There is some reason for concern if this species is going to survive. How is that going to happen in an urban environment where you also have people?”

Coyotes have spread across North America from their native range in parts of the western United States, taking advantage of the fact that larger predators – such as cougars and wolves – aren’t found in most of the eastern U.S. anymore.

“The general trend has been a decline in all carnivores, but there are some exceptions, and the coyote is one of the big exceptions,” Kays said.

Researchers wanted to know how coyotes might impact where native species like the gray fox are now found – especially since urbanization could affect how the two species interact by fragmenting their habitats and disrupting food sources.

“Foxes are fairly common in urban areas, perhaps in part because coyote numbers are relatively low,” said the study’s lead author Arielle Parsons, postdoctoral research associate at NC State. “In the Midwest and western United States, there are indications of ‘apparent decline’ in fox populations concurrent with coyote population increases. We don’t know if it’s a true decline yet, but there’s evidence it is.”

The researchers used wildlife photos taken by volunteers to figure out where foxes and coyotes coexist. The photos came from 915 motion-sensitive cameras that volunteers placed in yards, forest fragments and open areas in suburbs, dense suburbs, rural and wild areas. Researchers used the photos to develop a model of whether the two species are likely to be found together, and at what times.

From 347 pictures of coyotes and 943 pictures of gray foxes, they found that the two species are most likely to be found together in areas of high housing density and low forest cover – i.e, the suburbs. Coyotes were generally less likely to live in high density housing areas than the gray fox.

“These two species were more likely to use the same sites in suburban areas, especially small forested wood lots,” Parsons said. “We expected them to use these wood lots at different times to avoid each other, but actually we found that they use these suburban forest fragments at the same time.”

The researchers hypothesized that they could coexist in the suburbs because coyotes are just moving through, not establishing territories, and there are still relatively few of them.

“If they’re just moving through, they may not be as prone to direct competition, or bullying of the gray foxes, or their movements are hard for the gray foxes to predict,” Parsons said. “We also think gray foxes might not have a good way to avoid coyotes consistently in suburbs, since habitat is scarce, or avoidance isn’t necessary given abundant suburban resources.”

In rural areas, the two species were less likely to be seen together. However, gray foxes were more likely to inhabit a site as tree cover increased.

“Gray foxes are very good at climbing trees; they have sharp claws,” Kays said. “They’re one of the only dog relatives that can climb trees. Coyotes can’t. It could be that climbing trees helps them deal with coyotes.”

Researchers also saw a slight shift in the gray foxes’ timing, with the gray foxes more likely to be nocturnal around coyotes. 

Overall, researchers said findings for rural areas suggest gray foxes could be at risk in areas with few houses and little tree cover.

“In rural areas, where we’re seeing gray foxes spatially and temporally avoid the coyotes, that’s where we could see some impact on the gray fox population,” Parsons said. “It could mean the coyote is outcompeting, bullying or even killing gray foxes there. A strong competitive relationship may result in gray foxes not being able to access high quality areas, forcing them to establish themselves elsewhere where resources may not be as abundant. That could be a mechanism behind a decline.”

They found an important benchmark of tree cover is important for gray foxes in rural areas: Tree cover in more than 50% of a 1-kilometer radius resulted in gray foxes being more likely to occupy a site.

“Enhancing and preserving tree cover as much as we can is going to be beneficial for gray foxes,” Parsons said.

Researchers said another takeaway is that humans can impact how species are able to adapt and coexist.

“There are things we can do to change the ways wildlife species are able to adapt to human-dominated environments,” Parsons said. “Reducing habitat fragmentation and preserving forest and green spaces can help enhance the ability for these species to coexist.”

The relationship is evolving over time, they added, and could change. Researchers are continuing to study the populations of the two species over the long term.

The study, “The effect of urbanization on spatiotemporal interactions between gray foxes and coyotes,” was published online in Ecosphere on March 20, 2022. It was authored by Kays, Parsons, Kenneth Keller, Christopher Rota, Stephanie Schuttler and Joshua Millspaugh. The study was funded by the National Science Foundation through grants 1232442 and 1319293 and the North Carolina Museum of Natural Sciences.

-oleniacz-

Note to editors: The abstract follows.

“The effect of urbanization on spatiotemporal interactions between gray foxes and coyotes.”

Authors: Arielle Parsons, Kenneth Keller, Christopher Rota, Stephanie Schuttler, Joshua Millspaugh and Roland Kays.

Published online in Ecosphere on March 20, 2022.

DOI: 10.1002/ecs2.3993

Public conservation voting on restoring gray wolves to Colorado

Author contact: Mark Ditmer (mark.ditmer@gmail.com)

Over 3 million voters in Colorado recently weighed in on Proposition 114, a ballot measure to restore the gray wolf to its former range within the state. Previous public opinion polls suggested widespread support for wolf restoration, but the proposition passed with only a slim margin (50.9% of the total vote), and according to new research from Colorado State University scientists, there was a strong relationship between support for the ballot initiative and political support for the Democratic candidate for president in the 2020 election. Additionally, areas closer to proposed wolf restoration areas showed less support for the ballot initiative. Without considering presidential votes, there was a positive relationship between educational attainment and support for wolf restoration. However, when accounting for presidential votes, the team found that voters for President Biden in precincts with lower levels of education had relatively higher levels of support for wolf restoration than voters in precincts with higher educational attainment.

Previous studies have explored the relationships between demographics, livelihood, and self-reported attitudes and beliefs, but few have examined how these factors correspond to actual public behavior, i.e. voting.  

Read the article: Socio-ecological drivers of public conservation voting: restoring gray wolves to Colorado, USA.

Human disturbance is the most crucial factor for lynx in habitat selection

 Habitat selection in wildlife is a process that occurs at different scales: Balancing advantages, such as high abundance of food, with disadvantages, such as human disturbance. Large predators, with their large spatial requirements, are particularly sensitive to these disturbances. A team led by conservation biologists Prof. Dr. Marco Heurich and Joseph Premier from the Faculty of Environment and Natural Resources at the University of Freiburg has studied this habitat selection process in Eurasian lynx. Their results, published by the researchers in Biological Conservation, provide important information for the conservation of this species in human-dominated landscapes. "Through this study, we can generalize the habitat selection behavior of a large carnivore species on a continental scale fort he first time," explains Heurich.

Large dataset with animals in several European areas

The researchers led by Heurich and Premier used a data set consisting of tracking data on 125 lynx from nine study areas across Europe. They compared the locations available to and actually used by the predators at two scales: the landscape scale, which shows how lynx place their home range in the landscape, and the home range scale, which shows how lynx select the habitats within their home range. For this comparison, the research team used a novel machine learning approach called the random forest. This was extended to include a random effect so that variability within and between study areas could be accounted for.

What the animals avoid and how they orient themselves

On the landscape scale the analysis revealed that lynx avoid roads and human settlements. On the level of their home range, the animals were oriented towards hiding places and the availability of prey. The researchers found only minor differences between female and male lynx in their choice of habitat.

Heurich and Premier found the greatest differences in lynx habitat choice at the landscape level, where there were clear differences between the various study areas, for example between the Swiss Alps and the plains of Estonia. Within the foraging areas, lynx behaved very similarly throughout Europe, preferring heterogeneous forest areas and areas that provided protection from human disturbance.

Fishers facing pressure from wildfires, salvage logging,

 

IMAGE: FISHER, MIDSIZE CARNIVORE OF N. AMERICAN FORESTS. view more 

CREDIT: OREGON DEPARTMENT OF FISH AND WILDLIFE

. – The recovery of the fisher, a charismatic, long-tailed forest carnivore, will likely be hindered by the increasing frequency and intensity of future wildfires, new research by Oregon State University indicates.

A long-term monitoring program along the Oregon-California border showed that fisher abundance declined following three mixed-severity wildfires and that salvage logging also affected fisher populations negatively, said David Green of the OSU Institute for Natural Resources.

“We estimated a 27% reduction in the total number of fishers within our study area following the fires,” added Green, who led the study published today in Ecosphere.

Fierce and secretive, the fisher is an animal of conservation concern whose numbers dwindled in the 19th and 20th centuries due to fur trapping and logging. It’s a member of the Mustelidae family, which also includes wolverines, badgers, otters and minks, and it is native only to Canada and the northern United States.

“The fisher has a limited distribution, and rapid changes to forest structure could threaten its long-term persistence,” Green said.

Despite what they are called, fishers don’t prey on fish. They are so named because early North American settlers noticed a resemblance to the European polecat, which was also called a fitch, fitchet or fitchew.

Roughly the size of a large house cat, fishers not only scale trees but are able to climb down headfirst thanks to hind feet that can rotate almost 180 degrees. That trick helps them carry their offspring in their mouths as they climb up and down trees and may also help them attack prey from above.

The largest fisher population in the western United States is in what scientists refer to as the Klamath-Siskiyou Ecoregion, a 50,000-square-kilometer area straddling the Oregon-California border that has an estimated fisher density of about six per 100 square kilometers.

The researchers monitored fishers and gray foxes on a 465-square-kilometer portion of the ecoregion and examined the impacts of three mixed-severity wildfires – the Beaver, Gap and Happy Camp Complex fires – that burned 26% of the area in the summers of 2014 and 2016.

“A century of fire suppression plus increasingly frequent and long periods of drought are predicted to lead to more frequent and more intense wildfires across the West,” Green said. “Understanding the effects of wildfire on the species that live in forests, and the interactions among species, is important for making the most effective conservation and management decisions. The short- and long-term consequences are unclear for wildlife amid the calls for restoring forests to their natural regimes of frequent, low-severity fires.”

Wildfires, especially high-severity fires, cause vegetation changes that can make an area uninhabitable, he said. Salvage logging and replanting add more layers of complexity and make it harder to understand how wildlife respond to wildfire.

Green and collaborators from OSU, North Carolina State University and the U.S. Forest Service used six years of data from a long-term monitoring program to analyze the effects of fire and salvage logging on a population of fishers as well as a population of gray foxes.

Gray foxes are similar in size to fishers and compete with them for prey. Determining the effects of wildfires on gray fox populations and understanding how gray foxes and fishers interact is important for fisher conservation, Green said.

“Fisher abundance decreased significantly in areas of low-, medium- and high-severity wildfire,” he said. “Gray fox abundance decreased in the years before the wildfires but then rebounded.”

Abundance refers to a species’ relative representation in a particular ecosystem – in this case, how many fishers and foxes there are in the study area compared to other animals who share the area.

The researchers also looked at population density – the number of animals per unit of area. They found that medium-severity wildfires had a negative effect on gray fox density but high-severity fire had a positive effect. Salvage logging negatively affected both fisher and gray fox density, the study showed.

“Our results suggest that increased severity, extent and frequency of wildfires in the western United States will have negative impacts on fisher populations and change community composition for medium-size predators,” Green said. “We found that the wildfires that occurred in the Klamath-Siskiyou Ecoregion affected fisher density negatively regardless of burn severity, while gray fox density decreased in areas that burned at medium severity and increased in areas that burned at high severity.”

The researchers aren’t sure why the different severity levels had differing impacts on the two animals studied. More information on the long-term effects of fire and salvage logging on carnivores is needed, Green said, especially regarding changes in survival or reproduction.

New research shows that the effects of wolves on the recovery of aspen has been exaggerated by how it was measured

Peer-Reviewed Publication

S.J. & JESSIE E. QUINNEY COLLEGE OF NATURAL RESOURCES, UTAH STATE UNIVERSITY

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IMAGE: PREVIOUS RESEARCH SHOWED STRONG POSITIVE GROWTH IN YOUNG ASPENS IN YELLOWSTONE NATIONAL PARK AS THE ELK POPULATIONS DECREASED—A WELCOME RESULT. BUT NEW RESEARCH SHOWS ASPEN RECOVERY IS NOT AS ROBUST AS PREVIOUSLY THOUGHT. view more 

CREDIT: PHOTO COURTESY LAINIE BRICE

It’s an environmental success story that feels like a parable—the reintroduction of wolves in Yellowstone National Park in the mid-1990s triggered a cascade of effects that ultimately restored the ecosystem, including the recovery of aspen trees. But like many stories based on ecological realities, it’s more complex than at first glance—aspen recovery in the park is not as robust as generally believed, according to new research.

The Yellowstone story is a textbook example of a trophic cascade, in which predators help plants grow by eating or scaring away herbivores that eat the plants. When wolves were reintroduced into the Yellowstone food chain, they helped to reduce numbers of elk, which had been consuming young aspen trees. Previous research showed strong positive growth in young aspen as the elk populations decreased—a welcome result, as aspen forests have been vanishing from the northern Yellowstone landscape for the last century.

But new research from Elaine Brice and Dan MacNulty, from Utah State University’sDepartment of Wildland Resources and Ecology Center, and Eric Larsen, from the University of Wisconsin Stevens Point’s Department of Geography and Geology, shows that the effect of wolves on the recovery of aspen has been exaggerated by how it was measured.

Previous studies evaluated aspen recovery in Yellowstone by measuring the five tallest young aspen within a stand. The reasoning was that the tallest young aspen trees represent a ‘leading edge’ indicator of the future recovery of the entire aspen population. But this is not the case—sampling only the tallest young aspen estimated a rate of recovery that was significantly faster than was estimated by random sampling of all young aspen within the stand, according to the research.

“These are extremely complex systems, and understanding them is a major challenge because they are difficult to properly sample,” said Brice. “The traditional method of sampling by only using the tallest young aspen plants to measure growth—which most research currently relies on—doesn’t capture the entire picture.”

For one, elk are picky about the aspen they consume. They tend to eat plants at shoulder height for which they don’t have to crane their necks. As the leader stem (main trunk) of a young aspen grows past the shoulder height of adult elk, it is decreasingly likely to be eaten as it grows taller, said MacNulty. “This means that the tallest young aspen grow faster because they are taller, not because wolves reduce elk browsing,” said MacNulty. This finding highlights the complicating fact that height of young aspen is both a cause and an effect of reduced elk browsing. 

Taller aspen also thrive because they tend to have the best growing conditions (sunlight, moisture, soil quality). Measuring just the tallest young trees downplays the role of these other factors that have nothing to do with elk or wolf populations. And measuring just the tallest aspen also overlooks the failure of some young aspen to regenerate in the first place.

“That’s like calculating a team’s batting average without the player who always strikes out,” said Brice. Random sampling from the research showed an absence of aspen regeneration in some places, a vital piece missing from the initial measurements.

Understanding how ecosystems respond to changes in large predator populations is vital to resolving broader debates about the structure of food webs, determining species abundance and delivering ecosystem services, said the authors. This study demonstrates how deviations from basic sampling principles can distort this understanding. Non-random sampling overestimated the strength of a trophic cascade in this case, but it may underestimate cascading effects in other situations. Randomization is one of the few protections against unreliable inferences and the misguided management decisions they may inspire, they said.

“The bottom line is that ecologists must stick to classic principles of sampling design, like randomization, to fully understand trophic cascades in complex wildlife systems like Yellowstone,” said MacNulty.

Carnivore interactions are a game of risk and reward

 Coyotes can eat by scavenging cougars' prey but it's a risky proposition as coyotes often end up killed by cougars too, a new study of predator interactions by Oregon State University shows.

Researchers in the OSU College of Agricultural Sciences also looked at black bears and bobcats and found the interplay within the four-species "guild" of predators defied simplistic description.

Findings, published today in the Proceedings of the National Academy of Sciences, challenge the traditional model for carnivore interactions among species: that dominant predators suppress the other ones.

The study, one of the first to quantify rates of both scavenging and intraguild predation, is important because understanding the influence of dominant predators is necessary for anticipating the ecological effects of changes in carnivore populations.

Factoring in the study area's cougar and coyote density, the findings suggest nearly one-quarter of the area's coyote population is killed by cougars each year, although in many cases, coyotes did not appear to be killed while scavenging.

"That kill percentage estimate implies a strong suppressive effect counteracting the benefit to coyotes provided by the cougars," said Oregon State Ph.D. student Joel Ruprecht. "Overall, the issue of whether subordinate species incur a net fitness cost or benefit from dominant predators is far from resolved."

Coyotes seem to readily accept the risk of being near a cougar if a food reward is available, possibly because they can manage the risk by being extra vigilant, he added. Also, if a dominant predator becomes satiated after feeding on a kill, it may not be motivated to kill other carnivores.

"Learning whether dominant carnivores kill subordinate carnivores for food or for the long-term benefit of removing a competitor needs to be the focus of further research," said OSU associate professor Taal Levi.

Ruprecht, Levi and Ph.D. student Charlotte Eriksson led the study, which also involved scientists from the Oregon Department of Fish and Wildlife, the U.S. Forest Service and the University of California, Santa Cruz.

Between 2016 and 2020 in the Blue Mountains of northeastern Oregon, researchers tagged a "guild" of predators -- 17 cougars, 17 coyotes, 11 black bears and six bobcats -- with GPS collars that recorded their location every few hours. Scientists also tested the animals' scat to see what they were eating.

"How often elk turns up in the scats of the subordinate predators is a proxy for how much scavenging they're doing because it's unlikely any of them are killing adult elk," Levi said. "That means if they're eating elk it's probably either via scavenging or preying on calves, but in the Blue Mountains coyotes and bobcats rarely kill elk calves; black bears are somewhat more likely to."

To further zero in on what the predators were eating, the scientists did ground searches based on clusters of cougar GPS locations -- indicating potential kills -- and set up cameras at 28 of the 128 confirmed kill sites. The cameras allowed for a daily tally of site visits by bears, bobcats and coyotes and thus enabled an estimate of scavenging rates.

"The traditional paradigm for species interactions among carnivores has stressed hierarchies: Dominant predators curb the efforts of the next level, the mesopredators," Levi said. "We found evidence of that but also evidence of facilitation. The coyotes we studied had a strong attraction to kill sites, frequent carrion in their diet and high scavenging rates, compared to two indicators of suppression: They avoided cougars and also were preyed on by them."

There was no evidence to suggest coyotes' attraction to kill sites was lessened if a cougar was around, he added, indicating coyotes' willingness to disregard cougar risk if a food reward was present.

Bears had moderate scavenging rates and ate moderate levels of carrion but showed a statistically significant aversion to being around cougars. Nothing suggested bears were particularly attracted to kill sites or suffered predation at the hands of cougars, or that cougars had any effect at all on bobcats.

"Bobcats were indifferent to both cougars and their kill sites," Ruprecht said. "And bobcats weren't avoiding coyotes in general, meaning coyote presence was probably not a primary reason bobcats didn't feed on cougar kills."

There were coyotes on the scene at 89% of carcasses, bears at 50% of carcasses outside the hibernation period and bobcats at none of them.

Scat analyses showed elk in 58% of coyote scats and deer in 12%, comparable to the percentages for cougar scats (61% and 22%). Bear scats contained elk 29% of the time and deer 8% of the time. No bobcat scats provided evidence they had eaten elk, and 8% of bobcat scats contained deer.

"Investigations of the cougar kill sites showed that elk represented 64% and deer 16% of the prey items killed by cougars," Levi said. "Investigations also showed that coyotes represented 7% of cougar kills. In eight cases coyotes were the only prey item found, and in one case a dead coyote was found along with another prey item."

The bobcat findings were particularly surprising, he noted, because bobcats are known to scavenge from and be eaten by cougars in other locations, and also because it's usually more likely for a wild cat like a cougar to kill another species of cat than a predator from outside their taxonomic family.

"By foregoing the energy benefits they could gain from eating on cougar kills, and in doing so reducing mortality risk, bobcats in our study area approached the risk-reward tradeoff quite differently than the coyotes," he said. "But scavenging is only optimal under a specific set of conditions that also includes the probability of finding other food sources, and the energy required to search for them. The coyotes we studied faced little risk except from cougars and scavenged profusely; they're probably less likely to scavenge when there are lots of competitors for each carcass."

Southeast’s gray foxes may be struggling for survival

Competition for food from coyotes seems to be key to declining populations

Peer-Reviewed Publication

UNIVERSITY OF GEORGIA

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IMAGE: GRAY FOX POPULATIONS SEEM TO BE DECLINING IN THE SOUTHEAST, ACCORDING TO UNIVERSITY OF GEORGIA RESEARCH. view more 

CREDIT: SARAH WEBSTER

For generations, gray foxes have been part of the Southeastern landscape. They, along with red foxes, are among the carnivores that dine on a range of smaller animals, plants and berries.

But a new study published by researchers from the University of Georgia suggests competition for food from coyotes—a relative newcomer to the Southeast—may be putting pressure on foxes, particularly the gray fox.

“Gray fox populations, especially in the Southeast, seem to be declining, and have been for some decades,” said James Beasley, an associate professor in the UGA Warnell School of Forestry and Natural Resources whose doctoral student, Sarah Webster, wrote the study as part of her dissertation.

The study, published in the Journal of Mammology, was co-authored by Beasley as well as Warnell professor Michael Chamberlain and Warnell alumnus Joseph Hinton.

By looking at reports given by licensed animal trappers in South Carolina, where Beasley’s lab is located, it was clear to the researchers that the number of harvested foxes—particularly gray foxes—has been decreasing, while the number of harvested coyotes has increased.

“Here on the Savannah River Site, there are excellent historical trapping records and gray foxes used to be really abundant,” said Beasley. “But now we don’t see them nearly as frequently. That’s prompted questions of why—why are we seeing the reduction in these numbers?”

At the Savannah River Ecology Lab in Aiken, South Carolina, where the study took place, Beasley said habitats have changed dramatically over the years, from agricultural areas preferred by red foxes to forested areas more conducive to tree-climbing gray foxes. Also, food is abundant for generalist carnivores such as coyotes and foxes, which will eat a variety of plants and animals, and coyotes are now abundant in this landscape.

In the Midwest, where foxes and coyotes have lived together for hundreds of years, the species have found a way to carve out food sources without overlapping too much—scientists call this “partitioning.” But coyotes have only been in the Southeast since the 1970s, giving them far less time to sort out their overlapping food preferences.

Still, Webster wanted more information about how coyotes’ and foxes’ food sources might differ between the regions. So, she used hair samples gathered from red and gray foxes and coyotes from both regions and from a variety of decades, including preserved samples from the Georgia Museum of Natural History. By measuring the amounts of carbon or nitrogen in the hair, Webster was able to assess the amount of overlap in diet between each species.

For example, a diet high in protein would manifest as a higher nitrogen content. Vegetation, such as fruits or grasses, translates as carbon in the hair samples. By noting the relative amounts of carbon and nitrogen content in hair samples, Webster was able to assemble a picture of how much diet overlap there was between each species in each region.

The results? There are significant regional differences in how coyotes and foxes dine.

“In the Midwest, we found there were significant differences in diet between species, whereas in the Southeast they overlapped significantly,” she said. In the Southeast, red and gray foxes had a large amount of overlap in their diets prior to the onset of coyotes, and that overlapping continued once coyotes arrived, according to more recent samples. “So, all three species are overlapping now in the Southeast.”

Beasley noted that the diet partitioning that takes place among these species in the Midwest is something that developed over hundreds of years, as coyotes and foxes learned to navigate the landscape around each other. There apparently hasn’t been enough time for that dynamic to play out in the Southeast.

“The question is, will that happen fast enough, before the gray fox populations continue to decline further?” he added. “It’s not exceptionally dire for the gray fox, but we now often find them closer to buildings or other marginalized areas. So, they may be finding other mechanisms to coexist with coyotes. But they do need forested areas.”

Habitat is one way, said Webster, that we can work to ensure future populations of gray foxes remain stable. When we understand the dynamics at play between the species, we can better plan for the future.

“We don’t have good evidence that we can effectively manage coyote populations on a large scale. They’re generalists, and they’re too flexible in their behavior and patterns. They will survive just fine,” said Webster. “So, a more effective approach likely would be to focus on the gray fox. Step one is to better understand how the gray fox population is doing by studying their population dynamics, and then going forward from there and trying to build effective management around the gray fox to ensure they continue to thrive in the Southeast.”