New study identifies key success factors for large carnivore rewilding efforts

 

• The findings are based on data from almost 300 relocations of large carnivores, from wolves to bears;
• Relocations showed a high overall success rate, and a significant increase over recent years;
• Key factors that boosted survival of relocated animals included using younger animals, using wild-born animals, and including an acclimatisation period;
• Low mating success of relocated animals indicates ongoing challenges for rewilding programmes.

New research published today has identified the top factors that determine whether efforts to relocate large carnivores to different areas are successful or not. The findings could support global rewilding efforts, from lynx reintroductions in the UK to efforts to restore logged tropical forests.

 As apex predators, large carnivores play crucial roles in ecosystems, however their numbers have plummeted over recent decades. Relocating large carnivores can support their conservation, for instance to reintroduce a species to an area where it has been exterminated, or to reinforce an existing population to increase its viability. But to date, there has been little information about what factors determine whether these (often costly) efforts are successful or not.

The study was carried out by an international team led by researchers at the University of Oxford’s Department of Biology, Wildlife Conservation Research Unit (WildCRU), and School of Geography and the Environment. The group analysed data from almost 300 animal relocations which took place between 2007 and 2021. These spanned 22 countries in five continents, and involved 18 different carnivore species, including bears, hyaenas, big cats, and wild dogs.

Key findings:

• Overall, two thirds (66%) of the relocations were successful (where the animal survived in the wild for over 6 months).
• Success rates for large carnivore relocations have increased significantly since before 2007. For wild-born carnivores, success rates increased from 53% pre-2007 to 70%; and for captive-born animals, success rates doubled from 32% in pre-2007 to 64%.
• The species with the highest success rates included maned wolves, pumas, and ocelots which had a 100% success rate. The species with the lowest success rates (around 50%) were African lions, brown hyenas, cheetahs, Iberian lynx, and wolves.
• Overall, using a ‘soft release’ increased the odds of success by 2.5-fold. This involves acclimatising the animal to the new environment before it is fully released.
• Releasing younger animals (particularly 1 -2 year olds), also increased success rates. This may be because younger animals have greater behavioural plasticity to adapt to new environments, and they are less likely to have developed homing behaviours.
• For animals born in captivity, the success rate decreased by 1.5-fold, compared with animals born in the wild.
• However, just over a third (37%) of the relocated animals were observed to find a mate and/or raise a cub in their new habitat.

Although the fact that most relocated animals survived is encouraging, the authors say that the low mating success shows the ongoing challenges facing rewilding efforts and, crucially, the importance of protecting habitats that already exist.

Lead author Seth Thomas (Department of Biology, University of Oxford) remarked: ‘In the last 15 years we have become more successful at translocating and reintroducing large carnivores. This allows us to be optimistic for the future of rebuilding damaged ecosystems around the globe, but we must remember that it is always more important to protect large carnivore populations where they are now before we lose them. Even as we have grown to be more successful, 34% of individual translocations fail and they cannot be seen as a replacement for immediate conservation action to save these populations.’

In the near future, relocating large carnivores may become increasingly necessary as habitats become altered due to climate change, and if land use changes increase conflict between humans and animals.

In the UK, one of the most nature-deprived countries in the world, there have been calls to reintroduce formerly native apex predators, such as wolves and the Eurasian lynx.

Professor David Macdonald (WildCRU, Department of Biology, University of Oxford), a co-author for the study, said: ‘As the UN decade of ecosystem restoration gets underway, the ecological need and political appetite for relocations of large carnivores has never been greater, and they have the potential to contribute more now than ever before to biodiversity conservation. By scrutinising the most geographically comprehensive sample of relocated large carnivores to date, our study makes plain to conservationists and policy makers the urgency of improving rewilding efforts.’

Professor Alastair Driver, the Director of the charity Rewilding Britain (who were not directly involved in the study) said: ‘This study could not come at a better time here in the UK, with the devolved governments at last consulting positively on the merits of species reintroductions and various groups working hard on the feasibility of reintroducing species such as the European Wildcat and Eurasian Lynx. We still have a long way to go to overcome the misconceptions which dominate societal concerns around sharing our human-dominated landscape with other apex predators, but this report and the successes which it documents, will be hugely valuable in securing a more "grown-up" discussion on the subject. I have no doubt that this will, in turn, lead to well-planned and implemented carnivore reintroductions which only 10 years ago, I would have thought inconceivable in my lifetime.’

Dr. Miha Krofel (University of Ljubljana), a co-author who worked on lynx reintroductions included in the study said: ‘The main reason that allowed us to quantify the higher rate of success is the wider applicability of tracking technology compared to 15 years ago. Nowadays, many practitioners and scientists fit animals with tracking tags for better post-release monitoring of the translocated individuals. This allows us to learn from past releases to improve our interventions in the future.’

Caribou have been using same Arctic calving grounds for 3,000 years

 

IMAGE: ALASKA'S BARREN-GROUND CARIBOU HAVE BEEN USING THE SAME PARTS OF THE ARCTIC NATIONAL WILDLIFE REFUGE TO GIVE BIRTH TO THEIR CALVES FOR AT LEAST 3,000 YEARS, ACCORDING TO RESEARCHERS. view more 

CREDIT: MICHAEL MILLER

Caribou have been using the same Arctic calving grounds for more than 3,000 years, according to a new study by the University of Cincinnati.

Female caribou shed their antlers within days of giving birth, leaving behind a record of their annual travels across Alaska and Canada’s Yukon that persists on the cold tundra for hundreds or even thousands of years. Researchers recovered antlers that have sat undisturbed on the arctic tundra since the Bronze Age.

“To walk around the landscape and pick up something that’s 3,000 years old is truly amazing,” said Joshua Miller, an assistant professor of geosciences at the University of Cincinnati.

He has been leading summer expeditions to the Arctic National Wildlife Refuge since 2010, using rafts to navigate remote rivers to search for caribou antlers exposed on the tundra.

“We think about having to dig down into the soil to find that kind of ecological history, but on the Coastal Plain, the vegetation grows extremely slowly,” Miller said. “Bones dropped by animals that lived dozens or even hundreds of generations in the past can provide really meaningful information.”

The study demonstrates how important the area is for an animal that native Alaskans and Candians still depend on for sustenance, even as energy companies seek to exploit oil and gas resources in this protected area.

The Biden Administration in 2021 suspended drilling leases in the Arctic National Wildlife Refuge, the largest tract of undeveloped wilderness in the United States. 

“We know this region of the Arctic National Wildlife Refuge has been an important area for caribou for millennia,” Miller said. “That should give us pause on how we think about those landscapes.”

The study was published in the journal Frontiers in Ecology and Evolution.

Barren ground caribou undertake nature’s longest overland migration, traveling as far as 800 miles each year to reach their spring calving grounds in the Arctic National Wildlife Refuge and Canada’s Ivvavik National Park. The largest herd in this area, named for the Porcupine River, numbers in the hundreds of thousands of animals.

Scientists think caribou use these areas because they have fewer predators and offer seasonal vegetation near places where they can avoid the worst of the mosquitoes.

“The mosquitoes are horrible,” Miller said. “You get swarmed — literally covered in them. They can do significant damage to a young calf.”

Whatever the reason, the antlers they leave behind provide a physical record of their epic yearly travels that researchers can unlock through isotopic analysis. 

Caribou antlers, like those of elk, deer and moose, are made of fast-growing bone that the animals shed each year and regrow the following year.

“It is amazing to think that the oldest of the antlers found in our study were growing approximately the same time Homer was penning ‘the Iliad’ and ‘the Odyssey,’” study co-author Patrick Druckenmiller said.

He is director of the University of Alaska Museum and professor of the Department of Geology and Geophysics at the University of Alaska Fairbanks. Eric Wald from the U.S. Fish and Wildlife Service also co-authored the study.

The antler surveys in the vast expanse of the Arctic refuge require meticulous logistical planning, Miller said. Small planes deposit researchers and their gear deep in the interior, where they have to be watchful for grizzly and polar bears. They pilot rafts to the Beaufort Sea, conducting a  grid search of suitable caribou habitat identified in advance using aerial photography.

“We search for antlers along old river terraces, walking back and forth, covering every inch of habitat to find those ancient treasures,” Miller said. 

While male caribou antlers span four feet and weigh more than 20 pounds, female caribou antlers are much smaller. The antlers contain nutrients such as phosphorus and calcium that are important to plants and animals.

The dropped antlers create “nutrient sinks,” which could have a profound effect on the area’s vegetation. Miller said the caribou’s migration serves as a nutrient “conveyor belt” that might even draw caribou back to reap the benefits of this fertilizer in a reinforcement loop.

Caribou and other mammals are known to chew on dropped antlers for their valuable minerals. This could be an important dietary supplement for new caribou moms.

“We’d like to know to what degree this conveyor belt influences why caribou are going there in the first place,” Miller said.
The study was supported by the U.S. Fish and Wildlife Service, the National Geographic Society, the National Science Foundation, the Wildlife Society and the UC Office of Research.

Miller said the Arctic is warming faster than other parts of the globe. Parts of the Arctic that were once barren tundra are sprouting new spruce forests.

“We were in Arctic Village this summer, just south of the calving grounds, talking to elders about the changes they have seen,” Miller said. “Where once it was open tundra, large stretches of this barren ground are now full of trees everywhere. What will happen to the barren ground caribou as this habitat gets converted into forest?”

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JOURNAL

Frontiers in Ecology and Evolution

DOI

10.3389/fevo.2022.1059456 

Wolves eliminate deer on Alaskan Island then quickly shift to eating sea otters

 

 Wolves on an Alaskan island caused a deer population to plumet and switched to primarily eating sea otters in just a few years, a finding scientists at Oregon State University and the Alaska Department of Fish and Game believe is the first case of sea otters becoming the primary food source for a land-based predator.

Using methods such as tracking the wolves with GPS collars and analyzing their scat, the researchers found that in 2015 deer were the primary food of the wolves, representing 75% of their diet, while sea otters comprised 25%. By 2017, wolves transitioned to primarily consuming sea otters (57% of their diet) while the frequency of deer declined to 7%. That pattern held through 2020, the end of the study period.

“Sea otters are this famous predator in the near-shore ecosystem and wolves are one of the most famous apex predators in terrestrial systems,” said Taal Levi, an associate professor at Oregon State. “So, it’s pretty surprising that sea otters have become the most important resource feeding wolves. You have top predators feeding on a top predator.”

The finding were published today in PNAS.

Historically, wolves and sea otters likely lived in the study area, Pleasant Island, which is located in an island landscape adjacent to Glacier Bay about 40 miles west of Juneau. The island is about 20 square miles, uninhabited and accessible only by boat or float plane.

During the 1800s and much of the 1900s, populations of sea otters in this region were wiped out from fur trade hunting. Unlike wolves in the continental USA, Southeast Alaskan wolves were not hunted to local extinction. Only in recent decades, particularly with the reintroduction and legal protection of sea otters, have the populations of both species recovered and once again overlapped, providing new opportunities for predator-prey interactions between the two species.

The researchers studied the wolf pack on Pleasant Island and the adjacent mainland from 2015 to 2021. Gretchen Roffler, a wildlife research biologist with the Alaska Department of Fish and Game, and others from the department collected 689 wolf scats, many along the island’s shoreline.

Once the scat is collected, members of Levi’s lab in Oregon used molecular tools, such as DNA metabarcoding and genotyping of the scat, to identify individual wolves and determine their diets.

Roffler also captured and placed GPS collars on four wolves on the island and nine on the mainland. The researchers were curious whether wolves were traveling between the mainland and island, considering other scientists have found they are capable of swimming up to eight miles between land masses. Both the GPS collar data and genotypes of the scats confirmed they were not, indicating that the island wolf pack is stable and that the island is not a hunting ground for mainland wolves.

Locations from the GPS-collared wolves also provide evidence that the wolves are killing sea otters when they are in shallow water or are resting on rocks near shore exposed at low tide. Roffler and her crew have investigated wolf GPS clusters on Pleasant Island for three, 30-day field seasons since 2021 and found evidence of 28 sea otters killed by wolves.

“The thing that really surprised me is that sea otters became the main prey of wolves on this island,” Roffler said. “Occasionally eating a sea otter that has washed up on the beach because it died, that is not unusual. But the fact that wolves are eating so many of them indicates it has become a widespread behavior pattern throughout this pack and something that they learned how to do very quickly.

“And from the work we are doing investigating kill sites, we are learning that wolves are actively killing the sea otters. So, they aren’t just scavenging sea otters that are dead or dying, they are stalking them and hunting them and killing them and dragging them up onto the land above the high tide line to consume them.”

Shortly after wolves colonized Pleasant Island in 2013, the deer population on the island plummeted. With the wolves having consumed most of the deer, their main food source, Levi said he would have expected the wolves to leave the island or die off. Instead, the wolves remained and the pack grew to a density not previously seen with wolf populations, Levi said. The main reason, he believes, is the availability of sea otters as a food source.

The findings outlined in the PNAS paper build on research findings published in 2021 by the same researchers. In that paper they showed – in what they believe is a first – that wolves were eating sea otters. This was documented throughout the Alexander Archipelago, a group of Southeastern Alaskan islands which includes Pleasant Island.

The research has now expanded to study wolves and sea otters in Katmai National Park & Preserve, which is in southwest Alaska, about 700 miles from Pleasant Island. Early research by Ellen Dymit, a doctoral student in Levi’s lab, and Roffler indicates that wolves are also eating sea otters there. In fact, at that location Roffler and Dymit observed three wolves killing a sea otter near the shore

In addition to Levi and Roffler, co-authors of the PNAS paper are Charlotte Eriksson, a post-doctoral scholar in Levi’s lab, and Jennifer Allen, the environmental genetics lab manager in Levi’s lab. Levi is in the Department of Fisheries, Wildlife, and Conservation Sciences in the College of Agricultural Sciences.

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JOURNAL

Proceedings of the National Academy of Sciences

New research shows humans impact wolf packs in national parks

 

IMAGE: TRAIL CAMERA FOOTAGE OF THE SHOEPACK LAKE PACK WALKING ALONG A SANDY BEACH IN VOYAGEURS NATIONAL PARK IN THE FALL. view more 

CREDIT: CREDIT: VOYAGEURS WOLF PROJECT

New research shows how humans are a substantial source of mortality for wolves that live predominantly in national parks — and more importantly, that human-caused mortality triggers instability in wolf packs in national parks.

Published today in Frontiers in Ecology and the Environment, the study was led by Kira Cassidy, a research associate at Yellowstone National Park, and included co-authors at five national parks and University of Minnesota Voyageurs Wolf Project researchers Thomas Gable, Joseph Bump and Austin Homkes.

“For gray wolves, the biological unit is the pack or the family. We wanted to focus on the impacts of human-caused mortality to the pack, a finer-scale measure than population size or growth rate,” said Cassidy. “We found the odds a pack persists and reproduces drops with more human-caused mortalities.” 

While many studies have looked at how humans impact wolf populations, this study took a different approach and examined how human-caused mortality affects individual wolf packs. To do this, Cassidy and her team contrasted what happened to wolf packs after at least one pack member was killed by human-causes with packs where no members died of human-causes.

The researchers found that the chance a pack stayed together to the end of the year decreased by 27% when a pack member died of human causes, and whether or not that pack reproduced the next year decreased by 22%. When a pack leader died, the impact was more substantial, with the chance of the pack making it to the end of the year decreasing by 73% and reproduction by 49%.

Although the researchers did not examine whether human-caused mortality alters the size of wolf populations in national parks, this work shows that people are clearly altering certain aspects of wolf ecology in national parks even if they are not impacting overall population size.

One reason for this is that humans are a disproportionate cause of mortality for wolves that live predominantly in national parks. In other words, wolves die more often of human-causes than would be expected for the amount of time wolves spend outside of park boundaries. 

Of all national parks in the study, wolves in Voyageurs National Park spent the most time outside of park boundaries. In fact, wolves that had territories in or overlapping Voyageurs spent 46% of their time outside of the park. The result: 50% of all mortalities for these wolves came at the hands of people, with poaching being the most common cause of death.

“The unique shape of Voyageurs means that there are very few wolf packs that live entirely within the boundaries of the park. Instead, many wolf pack territories straddle the park border and when wolves leave the park, they are at an increased risk of being killed by people,” said Gable, a post-doctoral associate in the University of Minnesota’s College of Food, Agricultural and Natural Resource Sciences and project lead of the Voyageurs Wolf Project, which studies wolves in and around Voyageurs National Park.

However, Voyageurs was hardly unique as this pattern was similar across the other national parks in the study — Denali National Park and Preserve, Yellowstone National Park, Grand Teton National Park, and Yukon-Charley Rivers National Preserve — with human-caused mortality accounting for 36% of collared wolf mortality across all five parks.

Legal hunting and trapping of wolves outside of national park boundaries accounted for 53% of all human-caused mortality for wolves from national parks during hunting and trapping seasons.

These findings highlight why collaboration between different state and federal agencies is key when conserving and managing wildlife that go in and out of protected areas such as national parks. 

“Wildlife populations that cross hard boundaries from federal to state ownership are a challenge to manage. Wolves don’t know the park boundary lines,” said Bump, an associate professor in the U of M’s College of Food, Agricultural and Natural Resource Sciences.

The Voyageurs Wolf Project is funded by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).

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JOURNAL

Frontiers in Ecology and the Environment

DOI

10.1002/fee.2597 

Parasite may create risk-taking wolves in Yellowstone

Peer-Reviewed Publication

THE UNIVERSITY OF MONTANA

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IMAGE: UNIVERSITY OF MONTANA DOCTORAL STUDENT CONNOR MEYER, SHOWN HERE WITH A WOLF SKULL IN UM’S ZOOLOGICAL MUSEUM, STUDIES THE EFFECTS OF A PARASITE ON WOLVES IN YELLOWSTONE NATIONAL PARK. view more 

CREDIT: UNIVERSITY OF MONTANA PHOTO BY TOMMY MARTINO

MISSOULA – New research from a University of Montana student and his partners suggests that a common parasite associated with cats turns Yellowstone National Park wolves into risk takers, who when infected are much more likely to disperse across the landscape and become pack leaders.

The story caught fire with media outlets worldwide, with both CNN and NPR picking it up. The research originally was published in the journal Communications Biology.

“I’ve been blown away by it,” said Connor Meyer, a wildlife biology doctoral student in UM’s Ungulate Ecology Lab, part of the W.A. Franke College of Forestry & Conservation. “I’m surprised and grateful, but it’s been a bit of a nerve-wracking experience with all the attention.”

Meyer and his team created the story sensation by studying a single-celled creature named Toxoplasma gondii – often nicknamed the “mind-control parasite.” It prefers to live in felines, and infected cats spread spore-packed oocysts in their feces. T. gondii – which Meyer calls “toxo” for short – is the reason pregnant people aren’t supposed to clean the litterbox. Human immune systems usually keep it in check, but the parasite causes sickness that can be dangerous to fetuses, as well as those who are immunocompromised, such as HIV/AIDS patients.

T. gondii can infect all warm-blooded mammals, and it’s estimated a third of all people are carriers. The parasite settles in muscles and brains, and it’s known to boost dopamine and testosterone. This affects behavior: Studies have shown that infected rodents lose their fear of feline urine or cats and move around in the open more, making them more likely to be eaten. Infected captive chimpanzees lose their aversion to leopard urine.

It’s almost like they are being biologically controlled so the parasite can return to the comfy insides of its preferred feline host. But do other beasts get affected that aren’t part of the regular T. gondii life cycle?

Meyer and his fellow lead author, Yellowstone park biologist Kira Cassidy, started a serious study of the prevalence of T. gondii among park wolves in spring 2021. They discovered a toxo-positive wolf becomes more of a risk taker – 11 times more likely to disperse from its original pack and 46 times more likely to become a pack leader.

Yellowstone wolves are among the most studied animals in the world. Since they were reintroduced in 1995, park managers have taken blood samples every time a wolf is captured and collared. Meyer and his team wound up testing blood from 243 wolves for toxo antibodies with assistance from a Cornell University diagnostics lab. They also used data from long-term and ongoing Yellowstone Wolf Project research. More than 27% of the wolves they looked at – about 74 individuals all told – were infected with T. gondii.

The researchers first suspected wolves were getting infected by eating elk, their chief prey. But when they tested more than 100 elk, none were positive for the parasite.

“Eventually we found the most significant predictor of infection with wolves was when their range overlapped areas with high mountain lion density,” Meyer said. “So, with no elk testing positive, we hypothesized they were getting infected directly by cougars.”

Yellowstone wolves can slay and eat mountain lions, but there only have been 10 or so documented cases of that since 1995. Meyer said it’s more likely wolves they get toxo infection by nosing around “scrape sites,” where cougars defecate and mark their territory.

“We also have a litter box theory,” he said. “Almost anyone who has a dog and cat at home knows that, if the dog gets an opportunity, they are going to raid the litter box. We don’t have direct evidence of wolves eating mountain lion scat, but we have lots of photos of wolves at mountain lion scrapes. Wolves eat lots of things, so we don’t think it’s much of a stretch.”

Meyer said they want to emphasize they aren’t claiming that toxo causes wolves to become leaders.

“Toxo is not the only factor that predicts whether wolves will lead the pack,” he said. “It’s one of the many things that affect wolf behavior, just like in humans. With our study, being toxo-positive shortened the time it took for individuals to disperse, but toxo-negative individuals would still disperse and still become pack leaders. So we aren’t saying that toxo runs the world – we are saying it may accelerate some of these behaviors.”

He also said wolf packs generally have two leaders, a male and a female, and both are equally likely to test positive for the parasite.

A native of Whidbey Island, Washington, Meyer first became fascinated by the T. gondii life cycle as an undergraduate at the University of Washington. He then was hired by Dr. Matthew Metz – who earned his Ph.D. from UM last year – to work for the Yellowstone Wolf Project and soon after also began work with the Yellowstone Cougar Project. Over six years he worked on a variety of research efforts, which brought him into the orbit of Professor Mark Hebblewhite, leader of UM’s Ungulate Ecology Lab. Meyer started making inquiries about grad school.

“UM is one of the best – if not the best – wildlife biology graduate schools in the nation,” Meyer said, “so I definitely had an interest in coming here. Mark said working on the toxo paper could help me get into his program. I started at UM in 2021, working with Mark on an elk migration study in Canada. Doing this paper gave me a little more confidence as I jumped straight into a super-intense Ph.D. program.”

Though Meyer believes stories about T. gondii may be getting a bit sensationalized, and that too much may be attributed to its supposed mind-bending powers, he said we need to learn more about the parasite. Studies suggest that humans infected with toxo are more likely to like cats, develop schizophrenia or engage in road rage. He said a recent study on a college campus found students infected with toxo generally were rated more attractive.

Is it messing with our minds?

“More work definitely needs to be done,” Meyer said. “Luckily for us with our study, we had all that excellent data, we had all the blood serum and we had the time, interest and encouragement to check it out.”

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Disease outbreaks influence the color of wolves across North America

 New research from the University of Oxford, Yellowstone National Park, and Penn State, published today in the journal Science, may have finally solved why wolves change colour across the North American continent.

If you were to travel from Arctic Canada and head south down the Rocky Mountains into the US toward Mexico, the further south you go, the more black wolves there are. The reasons why have long puzzled scientists.

Professor Tim Coulson from the Department of Biology, University of Oxford who led the work explains, ‘In most parts of the world black wolves are absent or very rare, yet in North America they are common in some areas and absent in others. Scientists have long wondered why. We now have an explanation based on wolf surveys across North America, and modelling motivated by extraordinary data collected by co-authors who work in Yellowstone.’

Coat colour in wolves (Canis lupus) is determined by a gene called CPD103. Depending on the variant of the gene a wolf has, its coat can either be black or grey.

The researchers postulated that this gene also plays a role in protecting against respiratory diseases such as canine distemper virus (CDV). This is because the DNA region containing the gene also encodes for a protein that plays a role in defending against infections in the lungs of mammals. They predicted that having a black coat would be associated with the ability of wolves to survive an infection with CDV.

To test this idea, they analysed 12 wolf populations from North America, to examine whether the probability of a wolf being black was predicted by the presence of CDV antibodies. If a wolf has CDV antibodies, then it has caught CDV in the past and survived. They found that wolves with CDV antibodies were more likely to be black than grey. They also found that black wolves were more common in areas where CDV outbreaks occurred.

The researchers analysed over 20 years-worth of data from the wolf population at Yellowstone National Park. They found that black wolves were more likely to survive CDV outbreaks compared with grey wolves. These results led them to hypothesise that in areas where distemper outbreaks occur wolves should choose mates of the opposite coat colour to maximize the chance their cubs would have black coats.

They used a simple mathematical model to test this idea. Excitingly, the predictions from their model closely matched the observations that black and grey wolves were more likely to pair in areas where CDV outbreaks are common. This competitive advantage is lost in areas where CDV outbreaks do not occur.

These results are consistent with the idea that the frequency of CDV outbreaks across North America is responsible for the distribution of black wolves, because having the gene for a black coat may also provide protection against the virus. It also explains why mating pairs in Yellowstone, where canine distemper outbreaks occur, tend to be black-grey.

Peter Hudson, Willaman Professor of Biology, Penn State said ‘It’s intriguing that the gene for protection against CDV came from domestic dogs brought by the first humans entering North America, and the CDV disease virus emerged in North America many thousands of years later, once again from dogs.’

‘What I love about this study is how we have been able to bring together experts from so many fields and a range of approaches to show how disease can have remarkable impacts on wolf morphology and behaviour. We are learning that disease is a major evolutionary driver that impacts so many aspect aspects of animal populations.’

The researchers speculate that other species may follow a similar pattern to wolves. Many insects, amphibians, birds and nonhuman mammals have associations between colour and disease resistance. It might be that the presence a disease, or how frequently a disease outbreak occurs, is an important factor affecting the colour of mate an animal prefers.

Isle Royale Winter Study finds wolves living their best lives, moose not so much

 

IMAGE: TWO PUPS FROM THE EASTERN PACK TRY TO ROUSE PACKMATES FOR PLAY. view more 

CREDIT: SARAH HOY

Key findings include:

• A doubling of the wolf population, now estimated at 28 total wolves. “Each time we carried out aerial surveys this winter, we saw wolf tracks across many parts of the island and we also regularly saw groups of wolves traveling or resting together,” said Hoy. “It is such a pleasant change from five years ago when there were only two wolves on the island and the future of the wolf population looked pretty bleak. It just goes to show how quickly wolf populations are able to thrive in places where they are free from persecution.”

• A 28% decline in the moose population, from 1,876 to 1,346. Wolf kills accounted for 8.7% of the moose mortalities, the highest predation rate since 2011. Other challenges for the moose include blood-sucking winter ticks that weaken the animals, and spruce budworm infestations that kill balsam fir, their preferred winter food. “Over the past year we found an unusually high number of moose that appear to have died due to malnutrition,” Hoy said. “The population appears to be suffering from a food shortage, especially in winter when moose don’t have many good options of things to eat.”

For more information and to access the Winter Study report, read the full story at MTU News.