How do coexisting animals find enough to eat?

  

 

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Bison are seen grazing in a meadow in early winter at Yellowstone National Park. 

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Credit: Photo courtesy of Bethan Littleford-Colquhoun

PROVID Ecologists have long sought clarity on the dietary habits of different animal species. For scientists at Brown University and the National Park Service, it wasn’t obvious how herbivores in Yellowstone National Park, who subsist on grasses, wildflowers and trees, could compete for enough of those foods to survive the winter.

Over two years, with the aid of cutting-edge molecular biology tools and GPS tracking data, the researchers were able to determine not only what herbivores in Yellowstone eat, but also what strategies the animals use to find food throughout the year. The team published its findings in Royal Society Open Science.

“In Yellowstone, we know vegetation changes across seasons, but until now, we didn’t know how these seasonal changes influenced what animals eat or how they sustained themselves when options were limited,” said lead study author Bethan Littleford-Colquhoun, a postdoctoral research associate at Brown. “It turns out that while species eat similar categories of food, their diets differ from one another in cryptic and nuanced ways. And an animal’s body size plays an important role in how this is achieved.”

For decades, ecologists have debated how wildlife should confront challenges with their food supplies, said co-author Tyler Kartzinel, an associate professor of ecology, evolution and organismal biology at Brown.

Some experts argue that animals should diversify their diets to satisfy their taste preferences when they have the most freedom to select their favorite foods in summer, Kartzinel said. Others have posited that animals should diversify what they eat when they’re forced to accept whatever happens to be available — such as in a hard winter when they may have to compete for even undesirable foods to survive.

“These opposing predictions couldn’t both be true, so it wasn’t at all clear how Yellowstone's assemblage of herbivore species — with such a diversity of foraging behaviors — could succeed in finding enough food throughout the year,” Kartzinel said.

Seasonal specialization

For the study, the researchers used two years of GPS tracking and dietary DNA data to elucidate dietary variation across times of resource limitation and resource abundance for five of Yellowstone’s best-known species: bison, elk, deer, bighorn sheep and pronghorn antelope.

Scientists and staff at Yellowstone tracked the animals. Researchers at Brown, many of them undergraduate students overseen by Littleford-Colquhoun, analyzed fecal samples using a sophisticated molecular technique called metabarcoding, which helped to identify what foods the animals had consumed.

They found that all species capitalized on the seasonal abundance of wildflowers in summer, and that each species consolidated its foraging efforts around the subset of plant types that it was best prepared to compete for in winter. But the researchers discovered that feeding behaviors depended on the animal’s body size.

Members of the smallest species, such as deer and sheep, tended to fan out across summer meadows and dramatically expanded their diets before gathering in protected valleys where they survived the winter on leftover plants, according to the study. Larger animals like bison tended to do the opposite: In the winter, they were large enough to avoid competing for dwindling resources, so they instead ventured out into deep snow to find unique food reserves inaccessible to smaller deer and sheep.

“The study showed that these species can feed far more adaptably than anyone had previously assumed,” Littleford-Colquhoun said. “All species switch the ways they search for food, but the opportunities an individual bison has to fuel its migration or survive a hard winter might only work for it because it’s big. Meanwhile, other species might need to group together for protection in winter because they’re small.”

So when should animals search for unique foods to diversify their diets — summer or winter? Kartzinel said it depends on the kind of animal.

“Because of the variety of ways animals behaved in our study, we learned that both hypotheses about how animals fuel their migrations were right, but in different ways and at different times,” Kartzinel said. “So the question that biologists should have been bickering about for the past generation shouldn't have been, ‘Which foraging strategy is right?’ but rather, ‘When does each strategy work best for a given group of animals?’”

Kartzinel hopes the more nuanced insights about foraging behavior will help scientists take a more customized approach to wildlife conservation.

“If we want to help wildlife populations thrive,” Kartzinel said, “we should be maintaining a diversity of habitats and plant resources across their migratory corridors so that many animals, each with their own preferences, personalities and needs, can find what's best to fuel their journey.”

Wildlife tracking technology delivers promising results on polar bears

 

 Studying polar bears just became a lot easier with new “burr on fur” trackers which confirmed scientists’ belief that subadult and adult males spend most of their time on land lazing around, conserving energy until the ice returns.

A multi-institutional research team led by York University and including the University of Alberta, Environment and Climate Change Canada, Manitoba Sustainable Development, Ontario Ministry of Natural Resources and Forestry, and Polar Bears International, used three different “burr on fur” prototypes to study their effectiveness.

The paper, “Telemetry without collars: performance of fur- and ear-mounted satellite tags for evaluating the movement and behavior of polar bears,” published in the journal Animal Biotelemetry, details the first peer-reviewed examination of these new tracking devices that adhere to the fur of polar bears.

Studying polar bears is a difficult feat with current radio collars only suitable to be used on female bears leaving out a swath of the population, but new technology is providing researchers with a new tool which has confirmed the behaviour of adult male polar bears while on land waiting for the ice to form again.

Efforts to develop less-invasive tracking options and tools that could work on polar bears of both sexes and nearly all ages have been ongoing for years with varying success. Collars have been and remain the primary means of studying polar bear movements. More recently, ear tag transmitters have been used as a lighter-weight alternative. While both technologies serve an important role in helping study and conserve polar bears, researchers continually strive to develop methods that are both minimally invasive and provide quality data.

This led to a new tracking initiative known as “Burr on Fur,” which began as a challenge from Polar Bears International to 3M scientists, the global science and manufacturing company behind Post-It notes, to create a temporary, simple method for affixing small tracking units to polar bear fur. Three “Burr on Fur” prototypes were recently tested on wild polar bears along the coast of Hudson Bay, Canada, alongside traditional ear tag transmitters.   

The shortcomings with traditional tracking methods: The ear tag and “Burr on Fur” devices fill an important niche for scientists and wildlife managers. The new tags allow researchers to follow the movements of adult male and subadult polar bears, two groups that can’t be studied using traditional satellite collars. Adult males can’t wear collars because they slip off their cone-shaped necks and heads, and subadult bears grow too rapidly for safe collar use. Traditional ear tags are an alternative to collars. However, they currently require recapture to remove and, although rare, can pose a risk of injury to the ear. The new Burr on Fur tags are designed to be temporary, minimally invasive, and can be applied to both sexes and nearly all ages of polar bears.

“Successfully attaching telemetry tags to polar bear fur has never been done before, and we’re excited to share the results of this innovative work,” said Tyler Ross, lead author of the paper and researcher at York University, “The fur tags showed great promise, and give researchers the ability to study the behaviors and movements of polar bears that we have very little data on, like subadult and adult male bears.”

The study: 58 wild bears were tagged using ear tags and three distinct fur tag designs to compare both the duration of time the tags remained active while attached to the bears and the accuracy of the trackers. Applied alongside a traditional ear tag, which relied on an Argos Transmitter, the three fur tags were:

• The Pentagon Tag: this five-sided device included five holes punched into its corners, allowing tufts of fur to be pulled through. It utilized an Argos Eartag Satellite Transmitter.
• The SeaTrkr Tag: an oval-shaped tag that had 10 holes punched to allow 10 fur-tuft attachments. This design used an Iridium-linked Telonics GPS SeaTrkr-4370 transmitter.
• The Tribrush Tag: a triangle tag outfitted with tubes along its borders, through which pipe brushes ensnared the fur, twisting it inside the tubes. This tag used the same Argos transmitter as the Pentagon tags.

The research took place from autumn 2016 to 2021 with bears handled near Churchill, Canada, by the Polar Bear Alert Program and researchers at the University of Alberta, supplemented with operations by researchers at Environment and Climate Change Canada, Ontario Ministry of Natural Resources and Forestry, York University, and Manitoba Sustainable Development in 2021-22 near the Manitoba-Ontario border.

“Our results are an important step in better understanding the movements and behavior of polar bears, especially adult male bears, which are difficult to track because they can’t be fitted with satellite collars. Temporary, fur-mounted tags could also help track the movements of bears relocated after potentially coming into conflict with people, making these tags an important tool for conserving polar bears and keeping northern communities safe,” says York University Associate Professor and Sustainable Environmental Management Coordinator Gregory Thiemann, the report’s co-author.

Results: The top-performing fur tag was the SeaTrkr Tag, which remained attached to the bears for an average of 58 days and had superior accuracy due to its use of GPS/Iridium technology. In second place, the Trishbrush Tags remained attached for an average of 47 days. However, for the Tribrush Tag, the times varied widely, with one falling off after only two days while another lasted 114 days – the longest of all the tags.

Because they are permanently attached to the bears’ ears, the traditional ear tags remained in place for 137 days on average, while the shorter-term fur-based trackers proved to be reliable for shorter periods. The fur tags proved useful for monitoring bear behavior, and show great promise for future use in tracking polar bears, especially those that must be relocated after approaching too close to communities. Further testing and refinement are also being conducted on bears in zoos and aquariums through Polar Bears International’s Arctic Ambassador Center zoo and aquarium partners, allowing researchers to further refine the designs and see how they perform throughout different seasons. In the most recent round of zoo testing, a refined tag stayed on a bear for 75 days.

Important Data about Male and Subadult Polar Bears: The new data adds to our growing understanding of subadult and adult male polar bear movements and behaviors, which have been historically understudied because they cannot be safely collared for long periods. Findings confirm that adult and subadult male bears reduce their activity while on land, consistent with prior studies that showed bears spent approximately 70 to 90 per cent of their time resting during the ice-free period in Hudson Bay.     

Implications: While the ear tags remained attached to the bears longer, the temporary and easily affixed fur tags give scientists a new tool for enhanced tracking of bears for purposes of both applied research and managing human-bear interactions. The tracking tech could be applied to other types of bears, supporting efforts to reduce human-bear conflict, and future applications could include testing on other species with fur. While traditional tracking methods, such as collars, will remain critical for longer-term studies, the fur tags will prove a valuable tool, particularly for understanding and managing increasing wildlife-human interactions as the climate warms. 

“The collaboration between Polar Bears International, 3M, academic institutions, and governmental partners is a testament to our commitment to improving Arctic wildlife research and conservation technology,” says Geoff York, Senior Director of Research and Policy at Polar Bears International, adding, “These advancements will have tangible implications for wildlife management, aiding in tracking polar bears and promoting improved human-bear coexistence. We’re eager to further refine and deploy this pivotal technology.” 

About Arctic Sea Ice Day: These findings publish on July 15, which is Arctic Sea Ice Day, an annual event created by Polar Bears International to spark actions and conversations about the rapidly melting Arctic ecosystem, including its global significance and how people can help slow this warming trend. The Arctic is now warming nearly four times faster than the rest of the planet, causing the sea ice to melt, which causes polar bears to spend longer periods fasting on land.

Polar Bears International invites people to access the full report and urges the scientific community to consider the implications of these findings for further research and application in conservation and coexistence efforts.

Wolves’ return has had only small impact on deer populations in NE Washington

 

Peer-Reviewed Publication

 

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THE NEW STUDY FOCUSED ON THE WASHINGTON PREDATOR-PREY PROJECT’S STUDY AREA IN NORTHEAST WASHINGTON, SHOWN IN GREEN.

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CREDIT: TAYLOR GANZ

FROM: James Urton

(Note: researcher contact information at the end)

Humans drove wolves to extinction in Washington state around the 1930s. Thanks to conservation efforts, by about 80 years later, wolves had returned — crossing first from the Canadian border into Washington around 2008 and later entering the state from Idaho. Since then, wolf numbers in Washington have been steadily growing, raising questions about what the return of this large predator species means for ecosystems and people alike.

In northeast Washington, where wolves have recovered most successfully, researchers from the University of Washington and the Washington Department of Fish and Wildlife tracked one of their primary prey — white-tailed deer — in part to see what impact wolf packs are having on deer populations. The answer? So far, wolves aren’t having as much of an impact on deer as other factors.

In a paper published June 18 in Ecological Applications, the team reports that the biggest factors shaping white-tailed deer populations in northeast Washington are the quality of habitat available and a different, long-established large predator in the state: the cougar, also known as the mountain lion or puma. Wolves were a distant third in their impact.

“A big take-away from this study is that wolves are not returning to empty landscapes. These are places with humans and other carnivore species, like cougars, which will affect the impact that wolves can have,” said lead author Taylor Ganz, who conducted this research for her UW doctoral degree as part of the Washington Predator-Prey Project. “This area has a relatively high human footprint compared to other areas where wolves have been studied. These are not national parks or dense, old-growth forests. They are areas with active logging, farming, ranching and towns. Our findings show that these factors are likely limiting the impact of wolves on one of their primary food sources.”

It's not that wolves aren’t preying on white-tailed deer. According to the study, they are, just not enough to take a large bite out of the population as a whole.

White-tailed deer are widespread east of the Cascades. The state’s highest-density population of this species lies within the study area, which includes farmland and timber forests in parts of Stevens and Pend Oreille counties in northeast Washington. For the study, researchers radio-collared 280 white-tailed deer, 14 wolves, 50 cougars, 28 coyotes and 33 bobcats from 2016 to 2021. At the time of collaring, the researchers also noted vital statistics, including body condition, age and whether females were pregnant. When collared animals died, the team conducted a mortality investigation, if possible, and attempted to determine the cause of death.

The team, which also includes researchers with Washington State University and the Spokane Tribe of Indians, used the resulting dataset to estimate the growth rate of the white-tailed deer population over the four-year study, and to identify the major factors shaping it. The analysis determined that the white-tail population in the study area was likely stable, or slightly declining, but that wolves were not largely responsible.

The biggest factor impacting the deer population was habitat quality, including the amount of forage available for deer. For white-tailed deer, which are highly adaptable to human activity, foraging sites can range from forests and shrublands to agricultural fields. The study area includes both agricultural land and forests recently harvested for timber, both of which could provide deer with high-caloric density foraging sites, according to Ganz.

After habitat quality, the study found that predation by cougars had a smaller effect on the white-tailed population. Wolf predation had a still smaller impact. Bobcats and coyotes — both medium-sized predators — had a negligible impact on deer numbers.

“Studies like this provide valuable insights about the complexity of these systems and how managing predator and prey populations is challenging and dynamic,” said co-author Melia DeVivo, a research scientist with the WDFW. “It’s important to continue evaluating these systems to understand the impacts of management decisions. Prior to this study, one might have expected that relying solely on wolf management strategies would result in a booming deer population, when it is clearly more complex than that.” 

Since their return, the number of wolves in Washington has risen steadily, reaching a minimum of 260 in 2023, according to state researchers. Four wolf packs reside in the northeast Washington Predator-Prey Project study area. The total number of wolves in the study area — about 23 — remained steady overall during the research period.

The team’s findings contrast with studies of long-established wolf populations in protected areas, like Yellowstone National Park, which show a higher impact of wolves on the population dynamics of their prey species. To the authors of this new study, those differences highlight the importance of studying wolves in a variety of habitats.

“This study reminds us that the population dynamics of predator and prey species can vary quite a bit,” said senior author Laura Prugh, a UW associate professor of environmental and forest sciences. “Habitat quality, the species that are present and the degree of human activity all affect the impact that large predators like wolves will have. It’s critical to compare different types of sites.”

The paper is part of the Washington Predator-Prey Project, a partnership between the UW and the WDFW to investigate the impact of the wolves’ return on state ecosystems. Additional co-authors are Sarah Bassing , a UW doctoral alum in environmental and forest sciences; Lauren Satterfield, a UW doctoral student in environmental and forest sciences; biologists Brian Kertson and Benjamin Turnock with the WDFW; Lisa Shipley, a professor at WSU; Savannah Walker and Derek Abrahamson, both biologists with the Spokane Tribe of Indians; Beth Gardner, a UW associate professor of environmental and forest sciences; and Aaron Wirsing, a UW professor of environmental and forest sciences. The research was funded by WDFW, the National Science Foundation, the Rocky Mountain Elk Foundation, and the UW College of the Environment.

HYENAS VS. LEOPARDS

 

Peer-Reviewed Publication

 

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IMAGES FROM CAMERA TRAPS IN UDZUNGWA. FROM THE LEFT: FEMALE LEOPARD, HYENA, MALE LEOPARD

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CREDIT: RASMUS W. HAVMØLLER

Who’s stronger? A solitary leopard or cackle of hyenas? And which is best at getting along with humans?

University of Copenhagen researchers closely studied this in a large East African natural area surrounded by rural settlements. The study demonstrates that the presence of humans has a direct impact on the competitive relationship between the two large predator species: leopards (Panthera pardus) – the iconic spotted feline and the spotted hyena (Crocuta crocuta) – a kleptoparasite and pack hunter known for its comical appearance and characteristic 'laugh'.

"We humans continue eating our way into the little bit of wilderness left in the world. As we do, we impact wildlife. This study demonstrates that human disturbance upsets the balance between competing species and that this advantages hyenas," says Rasmus W. Havmøller, the study’s first author and a postdoc at the University of Copenhagen’s Natural History Museum of Denmark.

For months, Havmøller have been using camera traps to observe the dynamics between hyenas and leopards living in Tanzania’s Udzungwa Mountains – an approximately 2,000 km2 national park that is completely surrounded by agricultural and populated areas. The study is the first to combine camera observations of large predators over both time and space in a single analysis.

While the hyena as a species seems to be increasing in numbers, the population of leopards has been in significant decline for decades, both in Africa and worldwide. Since hyenas are the leopards' only competitor in this particular natural area, the ability of the two species to coexist is important for their survival. And here, the local population is an important factor:

"As the local people definitely don’t' like leopards, the leopards retreat as far away from humans as possible. Hyenas, on the other hand, benefit from the fact that humans don’t feel threatened by or pursue them. Consequently, hyenas live in close to human populations and may even exploit humans as shields against the leopards," says Havmøller.

"But the areas nearest to humans are also the areas with the most prey. And as hyenas assert dominance over these areas, it increases their ability to outcompete leopards and potentially threaten the leopard's adaptability," adds Havmøller.

Size matters

The researchers' observations confirm that size matters. While male leopards, which are larger, retain their dominance over hyenas, the situation is different for female leopards, which are smaller.

"Even though the male leopards are the ones in charge, the hyenas aren’t exactly scared off by them. They simply hang out in the background – probably to follow the leopards and steal their prey. But the physical inferiority of the hyenas seems to be compensated for in the areas closest to humans, because male leopards pull out," says Rasmus W. Havmøller, who continues:

"Female leopards, on the other hand, completely change their behavior when hyenas are in the area. They become diurnal, whereas hyenas are primarily nocturnal. This is probably because female leopards are smaller than hyenas, and that they will likely lose in any fight over prey."

Overall, the study shows that the hyenas benefit from living near humans.

"This suggests that the hyena's ability to adapt to areas of human activity may strengthen their overall success as a species and their competitive advantage over other large predators as we humans disturb more and more nature," says Havmøller.

When leopards are pressured, cascade effects may follow

According to the researcher, the shift in female leopard hunting patterns may have negative consequences:

"If you open up for more tourism and build more roads in the national park, the female leopards will be pressured immediately. They aren’t able to differentiate between safari tourists – who are most active during the day – and poachers. In time, they will probably learn that safari guests aren’t dangerous. But if there is a large and rapid influx into the area, you will probably see a decline in their population," says Rasmus W. Havmøller.

If leopards are seriously pressured out of the food chain, one should expect the emergence of what are known as cascade effects in the ecosystem:

"Plucking a large predator like leopards out of a food chain, which can be the ultimate consequence of human disturbances, may have very violent effects. Populations of other species, such as certain monkeys, whose populations are kept in check by leopards, will suddenly become too large and change the balance of the entire ecosystem," says the researcher.

As such, Havmøller hopes that the study will serve to encourage restraint when it comes to managing wilderness areas.

"Our results clearly indicate that human disturbances can change the competitive relationship between important predators. So, I hope that considerations will be made when expanding activities in wilderness areas, so as to roll them out slowly and give animals a chance to adapt. Furthermore, it would be good if the effects of human disturbances were monitored in more places using camera traps," concludes Rasmus W. Havmøller.

 

 

HYENAS VS. LEOPARDS 

• Leopards are unpopular among local people in many places because they may hunt livestock and attack humans. Hyenas, on the other hand, "clean up" by eating sick or dead livestock and don’t pose a problem for humans.
• Female leopards (approx. 20-43 kg.) are about half the size of male leopards (approx. 51-72 kg). Hyenas are in the middle in terms of weight (approx. 48-56 kg).
• Leopards are solitary hunters, whereas hyenas hunt in large cackles (clans), which can be an advantage for hyenas in confrontations with leopards.
• Hyenas are kleptoparasites that regularly steal the prey of other carnivores – including leopards.
• Leopards on the other hand, are masterful tree-climbers, which allows them to protect their prey from hyenas.

 

Idaho just voted to spend tens of thousands of tax dollars to kill even more wolves.

 

Under this new plan, ranchers are being reimbursed for hiring private hunting companies, which will be paid for killing wolves.   Wolves should be protected -- not gunned down for profit. Join our pack and help us defend wolves with a donation today.

Idaho has already been slaughtering as many as 500 wolves a year, but apparently they don't think that's enough.1   After years of radically expanded hunting and trapping, wolf numbers are already on the decline. Now, for the second month in a row, the Idaho Wolf Depredation Control Board has voted to spend vast sums of money to pay hunters for each and every wolf they kill.2   This is just a small part of the more than $1,000,000 that the state has set aside to finance the slaughter of gray wolves.3

1. Julie Luchetta, "Idaho Fish and Game approves plan to reduce wolf population from 1,300 to 500," Boise State Public Radio, May 12, 2023.   2. Rachel Cohen, "Idaho's wolf killings decline as board advances private contracts," Boise State Public Radio, May 10, 2024.   3. Keith Ridler, "Idaho wolf control board will have $1 million to kill wolves," Associated Press, January 19, 2022.

Wolves reintroduced to Isle Royale temporarily affect other carnivores

In a rare opportunity to study carnivores before and after wolves were reintroduced to their ranges, researchers from the University of Wisconsin–Madison found that the effects of wolves on Isle Royale have been only temporary. And even in the least-visited national park, humans had a more significant impact on carnivores’ lives.

The paper, published recently in Frontiers in Ecology and the Environment, uses DNA from foxes and martens’ scat and hair to understand where these animals were and what they ate before wolves were reintroduced, following the first year of their reintroduction, and as they formed packs across the island.

While many studies have been conducted to understand the effects of a carnivore reintroduction on their prey, less well studied is the effect of the reintroduction on other carnivores in the same food web, in this case foxes and martens.

“We had this really amazing opportunity in Isle Royale — where we had data before this large carnivore reintroduction and then following the reintroduction of wolves — where we could look at how these effects within carnivores are taking place, and how they shift,” says Mauriel Rodriguez Curras, who completed this work as a graduate student in the lab of UW–Madison forest and wildlife ecology professor Jonathan Pauli.

                  Isle Royale is a remote island in Lake Superior and its isolated geography and limited variety of animals — including moose, beavers and squirrels — make the island a relatively simple ecosystem in which to study the complexities of carnivore reintroductions.

                  Wolves first came to Isle Royale in the 1940s, likely by means of an ice bridge that formed naturally across 15 miles of Lake Superior from Minnesota or Canada to the island. Recently, climate change has kept ice bridges from forming as often, meaning new wolves can’t cross over to Isle Royale.

While the island once had 50 wolves across several packs, by 2018 there were just two wolves left: a father daughter duo that, due to inbreeding, were also half siblings. With the goal of restoring the natural apex predator to the island and rebalancing the ecosystem, 19 wolves were introduced by the park to Isle Royale in 2019.

For this study, a typical field day involved hiking between 15 and 20 miles of trail to check traps — open PVC tubes with little brushes inside them — for hair samples and looking for scat to swab and collect. Once back at UW–Madison, Rodriguez Curras and Pauli extracted DNA from both the samples and determined which individual fox or marten it was from. By measuring ratios of carbon and nitrogen present in the samples, they could also reconstruct the animals’ diets.

From their analysis, Rodriguez Curras and Pauli categorized the effects from wolves on other carnivores into three phases: absence, establishment and coalescence. The absence phase is data the lab had collected on foxes and martens the year before wolves were reintroduced to the island.

During establishment, which included the first year of the wolves’ reintroduction, no clear territories or packs had established, and the wolves were wandering the island mostly as individuals. Foxes altered where they hung out on the island in this phase, moving away from the dense forest and closer to campgrounds.

Since foxes compete with martens for food and have been known to kill them, martens normally stick to the densely forested areas of the island where it’s easier to hide. But, with foxes shifting to other areas of the island after wolf reintroduction, martens were able to expand their distribution on the island and increase their population.

Meanwhile, foxes found themselves facing greater risk. Foxes hunt small prey, but they often rely on scavenging. Theoretically, scavenging off wolf kills is beneficial to the foxes who couldn’t easily kill prey as large as a beaver or a moose calf. But to scavenge off those kills they would also have to be in areas the wolves are regularly, elevating the risk of being killed. So, rather than contend with wolves all the time, foxes supplemented their food by sticking close to campgrounds. They leveraged their cuteness and begging and raiding skills to target an easier meal: food from human visitors.

By 2020, the wolves had coalesced into packs with defined territories. The effects of wolves on the other carnivores disappeared, and foxes and martens occupied areas and ate food similar to the absence phase.

“The rewilding of these species is an important move that conservation biologists are making to try and reweave the fabric of ecosystem function,” said Pauli who’s been studying the island for 8 years. “But I think the point is that when we do this reweaving of communities, unexpected things happen. I don’t think these are bad things, but they’re not necessarily things that we’d immediately predict.”

Another unexpected consequence was how strongly human visitors to the island could affect these species interactions. Even though Isle Royale is considered one of the most pristine wilderness areas in the country and is one of the least-visited national park, Rodriguez Curras and Pauli found that humans, and the food they bring with them, have a significant effect on the relationship between the carnivores, where they live, what they eat and how they then interact.

Rodriguez Curras and Pauli credit their partnership with the National Park Service for providing the opportunity to conduct research that can guide ongoing and future carnivore reintroduction efforts in other areas. Their work revealing the way species interact with one another and with humans also provides Isle Royale National Park with the best available science to potentially improve visitors’ experiences while preserving the island’s wilderness.

New research illuminates the ecological importance of gray wolves in the American West

 

Peer-Reviewed Publication

CONSERVATION BIOLOGY INSTITUTE

 

IMAGE: 

A WOLF CHASES MAGPIES AND RAVENS FROM AN ELK CARCASS NEAR SODA BUTTE, YELLOWSTONE NATIONAL PARK

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CREDIT: NPS/JIM PEACO

Corvallis, OR — A study published today in the journal BioScience sheds light on the importance of gray wolves in western United States. Led by William Ripple, a scientist at Oregon State University and the Conservation Biology Institute, the research delves into the implications of large predator absence on plant and animal communities, and ecosystem functions. It calls attention to “shifting baselines” wherein increasingly degraded conditions are viewed as reflecting the historical state of a system.

"By the 1930s, wolves were largely absent from the American West, including its national parks. Most published ecological research from this region occurred after the extirpation of wolves," explains Ripple. "This situation underscores the potential impact of shifting baselines on our understanding of plant community succession, animal community dynamics, and ecosystem functions."

Age structure data for deciduous trees reveal substantial ecological impacts of elk and other ungulates following the removal of gray wolves from Yellowstone, Olympic, and Wind Cave National Parks. This has led to declines in long-term tree recruitment, influencing plant communities and ecological processes.

The study highlights the necessity of characterizing historical context and reference conditions when exploring areas where large predators, like wolves, are either absent, functionally extinct, or persist in reduced densities. The authors note that such areas likely occur in many regions of the world as a result of the widespread loss of large predators. Where applicable, the authors recommend that researchers include a discussion of how the presence or absence of large predators may have influenced their results and conclusions in future ecological studies in national parks.

"In addition to the loss or displacement of large predators, there may be other potential anthropogenic legacies within national parks that should be considered, including fire suppression, invasion by exotic plants and animals, and overgrazing by livestock," adds Dr. Robert Beschta, co-author of the study and emeritus professor at Oregon State University.

To address the effects of predator loss and other potential legacy factors, the study suggests that researchers investigate park archives to exploit historical data and information. National park archives can provide valuable insights into the history of predators and their prey, enabling scientists to discern among competing explanations for shifting ecological baselines.

"Studying altered ecosystems without recognizing how or why the system has changed over time since the absence of a large predator could have serious implications for wildlife management, biodiversity conservation, and ecosystem restoration," emphasizes Ripple.

The research underscores the importance of integrating historical context into ecological studies to provide a more comprehensive understanding of ecosystem dynamics. By acknowledging the historical presence of large predators and other anthropogenic legacies, as well as their potential ecosystem effects, researchers can contribute to more effective conservation and management strategies in national parks and beyond.

Recently, a coalition comprising nearly twelve conservation organizations initiated legal action against the U.S. Fish and Wildlife Service and the U.S. Department of the Interior. Their aim is to reinstate safeguards for gray wolves in Montana and Idaho, contending that the states' forceful hunting strategies endanger these wolf populations.

The research has implications for the long-term conservation of wolves and other large predators, including current gray wolf management and litigation in the West. "We hope our study will be of use to both conservation organizations and government agencies in identifying ecosystem management goals," added Ripple.

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JOURNAL

BioScience