Wednesday, June 7, 2017

Study doesn't support theory red and eastern wolves are recent hybrids, researchers argue



A team led by University of Idaho researchers is calling into question a widely publicized 2016 study that concluded eastern and red wolves are not distinct species, but rather recent hybrids of gray wolves and coyotes. In a comment paper that will publish Wednesday, June 7, in the journal Science Advances, the team examines the previous study and argues that its genomic data and analyses do not definitively prove recent hybridization -- but rather provide support for the genetic and evolutionary distinctiveness of red and eastern wolves.

"The history of these species is complex and certainly contains evidence for hybridization in the past. The question is timing," said Paul Hohenlohe, an assistant professor of biological sciences in the UI College of Science and the lead author of the comment paper. "The data and analyses aren't actually a good test of recent vs. older hybridization. In fact, the data are consistent with red and eastern wolves having a long evolutionary history as distinct lineages."

Hohenlohe co-authored the paper with an interdisciplinary team that included co-lead author Linda Rutledge, a research associate in the biology department at Trent University in Ontario, Canada; Lisette Waits, a Distinguished Professor in UI's College of Natural Resources Department of Fish and Wildlife Sciences; UI research scientist Jennifer Adams; UI postdoctoral researcher Kimberly Andrews; and other researchers from Trent, the University of Georgia and Northland College.

The team agrees with one conclusion of the previous study: Admixture is a part of the evolutionary history of North American canids, and conservation policy needs to take into account naturally occurring hybridization and population admixture. But they urge policymakers not to close the case on the origins of red and eastern wolves when making conservation decisions.

"Policymakers are making decisions about how much money, effort and energy to put into recovery and management efforts of the red wolf and eastern wolf," said Waits, who has served on U.S. Fish and Wildlife Service recovery teams for the red wolf. "It is important for them to understand that the conclusions stated in the vonHoldt et al paper are not universally supported by the scientific community, and there are alternative interpretations and remaining questions about the evolutionary history of canids in North America."

The UI-led team addresses several concerns with the previous study, which was led by Princeton University's Bridgett vonHoldt and published in Science Advances in July 2016. The team questions the vonHoldt study's use of genomic data from a few individual coyotes and eastern wolves that may not be the best representatives of those groups, as well as the authors' conclusion that genomic data demonstrate a lack of unique ancestry in red and eastern wolves.

The team's review of the vonHoldt study's analyses of genomic data finds the data do not establish definitive evidence for a recent hybrid origin of red and eastern wolves, but rather are consistent with multiple evolutionary possibilities. These possibilities include red wolves originating from a hybridization event tens of thousands of years ago, or diverging as a distinct lineage as long as 100,000 years ago and experiencing some subsequent hybridization.

The UI-led team finds that other data from the previous study, such as the amount of unique genetic variation found only within red or eastern wolves, further support the genetic distinctiveness of these taxa.

Hohenlohe, Waits and their collaborators are conducting further analyses about red and eastern wolf origins, and expect to continue to generate new data and hypotheses about the evolutionary relationships among these species, the gray wolf and the coyote.

"Genomics is an exciting new contribution to wildlife conservation, but it brings with it a responsibility to provide a coherent interpretation of complex data within the context of natural history," Rutledge said. "This is especially important for species at risk of extinction where the consequences involve the permanent loss of evolutionary potential. We get closer to the evolutionary truth when we use a holistic approach that includes multiple sources of information."

Tuesday, May 23, 2017

Wolves need space to roam to control expanding coyote populations


Wolves and other top predators need large ranges to be able to control smaller predators whose populations have expanded to the detriment of a balanced ecosystem.

That's the main finding of a study appearing May 23 in Nature Communications that analyzed the relationship between top predators on three different continents and the next-in-line predators they eat and compete with. The results were similar across continents, showing that as top predators' ranges were cut back and fragmented, they were no longer able to control smaller predators.
"Our paper suggests it will require managing for top predator persistence across large landscapes, rather than just in protected areas, in order to restore natural predator-predator interactions," said co-author Aaron Wirsing, an associate professor at the University of Washington's School of Environmental and Forest Sciences.
Gray wolves historically lived across vast swaths of North America, particularly in the western states and Canadian provinces. Coyotes, a smaller predator kept in check by wolves, appear to have been scarce in areas once dominated by wolves. As human development shrank territories for wolves, however, the wolf populations became fragmented and wolves no longer had the numbers or space to control coyotes, whose populations in turn grew.
The same story is at play in Europe and Australia, where the researchers examined the relationship between gray wolves and golden jackals, and dingoes and red foxes, respectively. As with America, when the top predator's range was slashed, the second-tier predators ballooned and ecosystems became imbalanced.
"This research shows that apex predators like dingoes and wolves need large, continuous territories in order to effectively control the balance of their ecosystems," said lead author Thomas Newsome of Deakin University and the University of Sydney in Australia. "Humans need a greater tolerance of apex predators if we want to enjoy the environmental benefits they can provide."
Only in the northern regions of Canada and parts of Alaska do wolves still roam across the large landscapes they once occupied. Elsewhere in North America, patchwork conservation efforts have brought wolves back in areas such as Yellowstone National Park, the northern Rockies, and eastern Washington and Oregon. Though wolves are on the upswing in these regions, their populations are likely too isolated to control the pervasive coyote and other small predators.
In some areas, the increase in wolves is actually helping some predators that might be a couple of rungs lower on the food chain, like the red fox. But regardless of whether the presence of more wolves helps or hurts other predators, that effect is likely dampened when wolf populations are fragmented.
This calls into question what makes for effective conservation. At least for wolves, Wirsing said, prioritizing activities that connect landscapes and attempt to rejoin isolated populations should be considered, he said.
"This reframes the debate ? what we really need to do is connect areas if we want predators to play their historical roles," he said.
The researchers used bounty hunting data from all three continents to map the top predators' historical ranges. They then mapped the range over time for the three smaller predators, looking to see where they overlapped. The researchers found that top predators such as wolves and dingoes could suppress coyotes, red foxes and jackals only when the top predators lived at high densities and over large areas. Additionally, wolves and dingoes exert the most control closest to the core of their geographic range.
In places like Yellowstone and eastern Washington and Oregon, however, smaller wolf populations are too far removed from the remaining core of the species' distribution to really make a difference in controlling coyote numbers.
Fewer wolves aren't the only reason coyotes have proliferated everywhere in North America. Coyotes are generalists that can live almost anywhere and have basically followed humans, eating our food and, in some cases, household pets. There have even been sightings in many metropolitan areas, including downtown Chicago.
"Coyotes have essentially hitched a ride with people," Wirsing said. "Not only do we subsidize coyotes, but we also helped them by wiping out their predators ? wolves."
The researchers plan to test whether similar patterns occur for other species pairs that compete strongly. They also call for more research comparing the ecological role of top predators on the edge of their geographic range, especially in human-modified environments.
"It will be interesting to see the influence of large predators on smaller predators in other parts of the world, especially the role of the big cats such as jaguars, leopards, lions and tigers," said co-author William Ripple of Oregon State University.

Friday, May 12, 2017

Measuring the impact of a changing climate on threatened Yellowstone grizzly bears



Climate change is altering the environment in Yellowstone National Park and its surrounding region and scientists at the University of California San Diego and Unity College are studying its impacts on the diets of threatened grizzly bears.

A study published May 11 in PLOS ONE focused on modeling the diets of grizzly bears in Cooke City Basin, Montana, part of an area designated as the Greater Yellowstone Ecosystem (GYE). Evidence from the team's research in the study area and a recent habitat-selection study by Montana State University indicates that grizzly bears continue to forage for whitebark pine seeds as a diet staple. Diet proportions derived from isotopic data, however, suggest that some bears could be responding to reductions in whitebark trees by consuming more plants and berries.
Once ubiquitous in western North America, the slow-growing whitebark pine trees have declined in recent decades and are now listed as endangered by the International Union for Conservation of Nature. Warming temperatures have led to shorter and milder winters, increasing beetle infestations and further threatening whitebark pine mortality. Other potential food sources for grizzlies such as trout and ungulates have also declined in the region. 
"Whitebark pine trees have declined due to an introduced fungal disease called blister rust, and, more recently, to increased infestation by the mountain pine beetle, which is exacerbated by climate change," said study coauthor Carolyn Kurle, an assistant professor at UC San Diego's Division of Biological Sciences. "Such declines further highlight the need to monitor diets of grizzlies as the environment continues to change."
Lead author Jack Hopkins, a former postdoctoral researcher in Kurle's lab at UC San Diego and currently an assistant professor at Unity College, and his team measured stable isotopes in bear hair and related their abundances to those found in their foods.
"Stable isotope analysis is a powerful ecological tool for reconstructing the diets of animals," said Hopkins. "Instead of investigating the diets of animals based on what's eliminated (feces), we estimate the importance of major food sources to animals based on what's assimilated into their tissues. Using stable isotope analysis to conduct a retrospective diet analyses can shed light on how animals, such as Yellowstone grizzlies, have responded to changes in food availability on the landscape."
Previous research has shown that whitebark pine seeds--often cashed in large middens by red squirrels--are raided by grizzlies in the fall, fueling reproduction and ensuring the survival of grizzlies in the region. A main reason threatened grizzly bears have remained protected for decades is because it has not been clear how declines in whitebark pine trees, and thus the seeds they provide bears, will impact population trends over the long term.
Because their inferences are limited to a small area in the region and a small number of bears, the researchers recommend a large-scale study and urge others to use their new modeling framework to investigate the diets of other species of concern.
"Such analyses could be used to monitor grizzly bear recovery efforts and inform other wildlife conservation and management programs worldwide," Hopkins added.

Tuesday, April 18, 2017

Only two Isle Royale wolves


For the second year in a row, the Isle Royale wolf population remains a mere two. Researchers from Michigan Tech say that as the wolf population stays stagnant, the moose population will continue to grow at a rapid pace. And this could have a significant impact on the island's famed forests.
According to Rolf Peterson, a research professor at Michigan Tech and co-author of the report, the Isle Royale wolves are no longer serving their ecological function as the island's apex predator--the creature at the top of the food chain. With only two wolves left on the island, the moose population has grown to an estimated 1,600. 
Without wolf predation, says John Vucetich, a professor of ecology at Michigan Tech and report co-author, the moose population could double over the next three to four years. And more moose means more vegetation is eaten. The observations were reported in this year's Winter Study, which marks the 59th year of monitoring wolves and moose on Isle Royale, the longest running predator-prey study in the world. 
Wolf Genetics
Where have all the island wolves gone? The answer lies in genetics. The population crash on Isle Royale is the result of inbreeding--the remaining wolves are not only father and daughter, they are also half siblings who share the same mother.
Researchers believe the two have probably mated at least once in the past: in 2015, an approximately nine-month-old pup was spotted with the two adults. That pup, however, did not appear healthy. Researchers noted a visibly deformed tail, small stature and possibly abnormal posture. Peterson and Vucetich were not surprised when the pup failed to appear with the adults in 2016.
The remaining wolves are not expected to successfully reproduce in the future, either. Both animals are approaching old age--the female is seven years old and the male is nine--and no one can predict how much longer either wolf will live. Further complicating matters, the female wolf has been observed aggressively rejecting the male as a mate.
But even if the pair were to produce a healthy pup, it would likely have little impact on the Isle Royale ecosystem. In the case of these wolves, extreme inbreeding makes the population's natural recovery unlikely. The wolves' numbers started plummeting in 2009, declining by 88 percent from 24 to 2 wolves. Vucetich and Peterson believe this is a result of inbreeding, and all geneticists who have studied the situation agree that recovery is unlikely without new genetic material.
At the end of 2016, the National Park Service published a Draft Environmental Impact Statement (DEIS) to determine how best to manage the wolves on Isle Royale. The DEIS discussed four potential courses of action. According to the document, NPS would prefer a time-limited introduction of new wolves--up to 20 to 30 wolves selected to maximize both genetic diversity and restore predation to the ecosystem. NPS estimates that the process to introduce the number of wolves identified in the plan would take between three to five years. Public review of the document concluded in mid-March, and the NPS is reviewing all comments. A final decision is expected in the fall.
More Moose 
The 2017 moose census puts the Isle Royale herd at approximately 1,600 members. According to the report, the multiyear trend shows the moose population has been growing at a six-year average rate of 21.6 percent. Peterson and Vucetich credit this rapid growth to several factors: high reproduction rates, low rates of mortality due to wolf predation, mild winters and an abundance of forage. 
But this abundance of forage may not last. According to recent findings, under the island's current conditions, the moose population could double over the next three to four years. If this happens, the number of Isle Royale moose would reach an unprecedented high for the project's six-decade history. And this could result in high levels of browsing on the island's vegetation.
"Everything we're seeing on Isle Royale is consistent with our past understanding of the ecosystem's dynamics," says Vucetich. "We have every reason to expect the moose population will continue to grow and increasingly impact the forest."
Moose aren't the only Isle Royale residents experiencing a population boom with a dwindling number of wolves. The report notes that the number of beaver colonies has increased dramatically over the past six years, from approximately 100 to nearly 300. 
"Wolves are the only significant predator of beaver on Isle Royale," says Peterson. "Beaver were nearly extinct across North America 200 years ago. At Isle Royale, they're now at unprecedented levels."
With wolves no longer serving their predatory function, Isle Royale's ecosystem could soon look dramatically different.

Thursday, April 6, 2017

Wolves often rely on human foods


On landscapes around the world, environmental change is bringing people and large carnivores together--but the union is not without its problems. Human-wildlife conflict is on the rise as development continues unabated and apex predators begin to reoccupy their former ranges. Further complicating matters, many of these species are now reliant on anthropogenic, or human, foods, including livestock, livestock and other ungulate carcasses, and garbage.

Writing in BioScience, Thomas Newsome, of Deakin University and the University of Sydney, and his colleagues use gray wolves and other large predators as case studies to explore the effects of anthropogenic foods. They find numerous instances of species' changing their social structures, movements, and behavior to acquire human-provisioned resources. For instance, in central Iran, gray wolves' diets consist almost entirely of farmed chickens, domestic goats, and trash.

Other instances of these phenomena abound. In a similar case in Australia, dingoes gained access to anthropogenic foods from a waste facility. The result, according to the authors, was "decreased home-range areas and movements, larger group sizes, and altered dietary preferences to the extent that they filled a similar dietary niche to domestic dogs." Moreover, wrote the authors, "the population of subsidized dingoes was a genetically distinct cluster," which may portend future speciation events. Hybridization among similar predator species may also contribute to evolutionary divergence: "Anthropogenic resources in human-modified environments could increase the probability of non-aggressive contact" between species. According to the authors, "If extant wolves continue to increase their reliance on anthropogenic foods, we should expect to observe evidence of dietary niche differentiation and, over time, the development of genetic structure that could signal incipient speciation."

Wolves' use of anthropogenic food could have serious implications for wider conservation efforts, as well. In particular, Newsome and his colleagues raise concerns about whether wolf reintroduction and recolonisation programs will meet ecosystem-restoration goals in human-modified systems. Managers will need to consider "how broadly insights into the role played by wolves gleaned from protected areas such as Yellowstone can be applied in areas that have been greatly modified by humans," say the authors.

Newsome and his colleagues call for further research--in particular, "studies showing the niche characteristics and population structure of wolves in areas where human influence is pervasive and heavy reliance on human foods has been documented." Through such studies, they argue that "we might be able to ask whether heavy reliance of anthropogenic subsidies can act as a driver of evolutionary divergence and, potentially, provide the makings of a new dog."


Thursday, March 23, 2017

Coyotes can't match wolves' hunting prowess



Eastern wolves once roamed forests along the Atlantic coast, preying on moose, white-tailed deer and other hooved mammals collectively known as ungulates. As the wolf population plummeted via the rifle and the trap, however, the eastern coyote inherited the status of apex predator in those habitats.
But a study from John Benson and colleagues provides evidence that the eastern coyote hunts moose and other large prey far less frequently than does the eastern wolf -- instead preferring to attack smaller game or scavenge human leftovers.
The findings help resolve long-standing questions about whether eastern coyotes have filled the ecological niche left vacant when the eastern wolf became threatened, Benson said.
"Wolves rely on large prey to survive," said Benson, assistant professor of vertebrate ecology who conducted the research as a doctoral student at Trent University. "But the smaller size of coyotes appears to give them dietary flexibility to survive on a wider variety of food and prey sizes, making them less predictable predators of large prey.
"Having a top predator that preys consistently on large animals like deer and moose may be an important part of maintaining stable predator-prey dynamics and healthy, naturally functioning ecosystems."
After GPS-tracking 10 packs of eastern wolves and analyzing their kill sites in Ontario, the team estimated that the wolves consumed 54 percent of their ungulate meat from moose and 46 percent from white-tailed deer. By contrast, eight packs of eastern coyote ancestry that occupied separate but neighboring territories got just 11 percent of their ungulate meat from moose and 89 percent from deer.
The eastern wolf weighs between 50 and 65 pounds; the eastern coyote typically hits 40 to 50. Though the extra weight gives eastern wolves a greater chance of killing a moose - or at least surviving the encounter - it also demands the greater caloric intake that moose and other meaty prey can provide.
Because wolves need to feed on large prey, their populations tend to rise and fall together, Benson said. Wolves may kill many moose during a winter, for instance, depleting their numbers. With fewer moose available, the wolf population declines, boosting the moose population, which in turn boosts the wolf population, and so on.
Yet the buffet-style menu of the eastern coyote means that its numbers can remain steady or even rise without large prey if alternative food is abundant. This opportunistic diet, Benson said, might also be driving erratic population swings among those lower on the food chain.
"It's important to understand the role that wolves play in ecosystems and to not assume that smaller predators ... perform the same ecological functions," Benson said. "If coyotes start hammering white-tailed deer, and deer start to decline, then (coyotes) can just eat rabbits or squirrels or garbage but continue to prey on deer, too. So we think that could be a destabilizing element.
"There are some areas where you've got way too many white-tailed deer in the east, and then you've got other areas where hunters are concerned because the deer are declining. That speaks to the fact that coyotes are an unpredictable predator."
The study is timely: Canada recently designated the eastern wolf as threatened, with the vast majority of eastern wolves living protected in Ontario's Algonquin Provincial Park.
Human-caused mortality has limited efforts to expand the population beyond Algonquin Park, Benson said, which is made worse by the fact that wolves there are likely naïve to the dangers posed by humans. Another issue: Eastern wolves readily breed with eastern coyotes in the wild, making it difficult to maintain a pure lineage.
"Is there a way to get them to expand numerically and geographically outside of the park? We're not sure at this point," said Benson, who provides advice to a team now developing a recovery plan. "One thing that can be managed is human-caused mortality, so if we can provide additional protection, that should put them on equal demographic footing.
"It's an incredibly challenging situation that is complicated by the interactions of these wolves with coyotes and humans. If the park stays the same, there's no immediate reason that they would go extinct. However, we wouldn't want to go forward with that as our only plan because it offers little chance for expansion."
Though large-scale reintroduction across eastern North America will probably not occur soon, Benson said the study emphasizes the value of preserving delicate predator-prey balances that ecosystems have calibrated over millennia.
"Our work suggests that there's an ecological role that wolves play that won't be played by other animals," he said. "That's probably a role that's worth conserving on landscapes, even outside protected areas. If we're interested in restoring landscapes to a more natural, functioning ecosystem, this would be an important part of that."

Monday, February 13, 2017

Snow leopard and Himalayan wolf diets are about one-quarter livestock


Around a quarter of Himalayan snow leopard and wolf diets are livestock, the rest being wild prey, according to a study published February 8, 2017 in the open-access journal PLOS ONE by Madhu Chetri from Inland Norway University of Applied Sciences, Norway, and colleagues.

Killing livestock creates conflicts between top predators and pastoral communities, and is a main challenge for conserving snow leopards, which are endangered, and Himalayan wolves, which are rare. These wolves prefer the open grasslands and alpine meadows that are also frequented by pastoral herders, and snow leopards prefer the steep terrain associated with montane pastures. To assess prey preferences of these carnivores, Chetri and colleagues analyzed DNA and hairs in 182 snow leopard scats and 57 wolf scats collected in the Central Himalayas, Nepal.

The researchers found that in keeping with the predators' habitats, snow leopards preferred cliff-dwelling wild prey such as bharal, while wolves preferred plain-dwelling wild prey such as Tibetan gazelles. In addition, livestock comprised 27% of the snow leopard diet and 24% of the wolf diet. Livestock occurred more than twice as frequently in scats from male snow leopards than in scats from females. Although livestock constitutes a substantial proportion of the predator's diets, little is known about the actual predation impact on the pastoral communities. Hence, the researchers' forthcoming work focuses on estimating livestock mortality rates and identifying factors associated with livestock loss.