Coastal Alaska wolves exposed to high mercury concentrations from eating sea otters

 

In late 2020, a female coastal wolf collared for a study on predation patterns unexpectedly died in southeastern Alaska. 

The wolf, No. 202006, was only four years old. 

“We spent quite a bit of time trying to figure out the cause of her death by doing a necropsy and different analyses of tissues,” says Gretchen Roffler, a wildlife research biologist with the Alaska Department of Fish and Game.

“What finally came up was really unprecedented concentrations of mercury in this wolf’s liver and kidneys and other tissues.”

Roffler was put in touch with Dr. Ben Barst, PhD, an assistant professor in the Faculty of Science at the University of Calgary who was working at the University of Alaska Fairbanks at the time.

They, along with a team of other scientists, have now published new research in the journal Science of The Total Environment that shows wolves eating sea otters have much higher concentrations of mercury than those eating other prey such as deer and moose.

Mercury found in high concentrations in predators

Barst, an expert in ecotoxicology, says mercury is a naturally occurring element humans release from the Earth’s crust through coal combustion and small-scale gold mining.

“It’s a really weird metal in that it’s liquid at room temperature or it can be a vapour,” he says. “When it gets into the atmosphere in its elemental form, it can travel for really long distances.”

Barst says it also gets converted into methyl mercury when it gets into aquatic environments.

“It’s an organic form of mercury that really moves quite efficiently through the food web, and so it can reach high concentrations in predators that are tapped into aquatic food webs," he says. "So, we see higher concentrations in wolves that are tapped into a marine system.”

The latest research compares wolves from Pleasant Island — located in the Alaska Panhandle region, west of Juneau — with the population on the mainland adjacent to the island, as well as wolves from interior Alaska.

“The highest concentrations are the wolves from Pleasant Island,” says Barst, noting that the mainland population mostly feeds on moose and the odd sea otter.

He says there could be a number of factors driving the higher concentrations of mercury, but they are still researching several possibilities. 

Mercury-wolf health impact examined

Researchers are also doing more work to determine mercury’s role in impacting wolf health, as it remains unclear exactly what caused the death of Wolf No. 202006.

Barst notes, however, that years of data collected by Roffler show that 70 per cent of the island wolves’ diet is sea otters.

“They're eating so many sea otters that they're just getting this higher dose of mercury and it accumulates over time,” he says.

Roffler says there are other populations of wolves in Alaska as well as in B.C. that appear to be eating sea otters.

“It turns out that this might be a more widespread phenomenon than we thought originally,” she says. “At first I was surprised it was happening at all.”

It’s not yet known whether the sea otters off the B.C. coast also contain high levels of mercury.

Potential link to climate change

Back in Alaska, Barst says there’s a potential link to climate change due to the state's shrinking glaciers.

“We know that glaciers can release a tremendous amount of mercury,” he says. “In coastal Alaska, glaciers are retreating at some of the most rapid rates in the world.

“With that melting of glaciers, you get release of the particulate bedrock and some of that bedrock contains mercury – and so we don’t really know the fate of that mercury. It may just get buried in sediments or it may actually be available for conversion to methyl mercury and get into the food web.

“That’s part of what we’re doing now.”

---

Journal

Science of The Total Environment

DOI

10.1016/j.scitotenv.2025.179542 

Who decides on removing grizzly bears from the endangered species list?

Guest editorial by Dr Kelly Dunning, Timberline Professor of Sustainable Tourism and Outdoor Recreation at the University of Wyoming

Peer-Reviewed Publication

Frontiers

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Dr Kelly Dunning's research focuses on biodiversity conservation and the human dimensions of natural resources in tourism prone areas.

view more 

Credit: Kelly Dunning

By Dr Kelly Dunning

The Endangered Species Act (ESA), now 50 years old, was once a rare beacon of bipartisan unity, signed into law by President Richard Nixon with near-unanimous political support. Its purpose was clear: protect imperiled species and enable their recovery using the best available science to do so. Yet, as our case study on the grizzly bear in the Greater Yellowstone Ecosystem reveals, wildlife management under the ESA has changed, becoming a political battleground where science is increasingly drowned out by partisan ideology, bureaucratic delays, power struggles, and competing political interests. The survival of the ESA, a wildlife policy mimicked all over the world, may depend on our ability to navigate these waters.

The grizzly bear, a cultural symbol of the American West, embodies this shift. Listed as threatened in 1975 when its numbers dwindled to fewer than 1,000 and its range contracted by 98%, the species has managed to come back from the brink. In the Greater Yellowstone Ecosystem, the population now exceeds 700, a number that surpassed recovery goals set by the federal wildlife management agency tasked with recovery, the US Fish & Wildlife Service. By the ESA’s own metrics, this is a success story, which now means the grizzly bear is eligible for ‘delisting’. Yet, attempts to remove federal protections in 2007 and 2017 were overturned by courts, not because the science was lacking, but because the process has become a lightning rod for political interests.

Our study looks at 750 documents and 2,832 stakeholder quotes to track this politicization. Historically, wildlife management is the strict domain of agency scientists in the executive branch. These scientists are experts trained to interpret interdisciplinary scientific data and balance both human and ecological needs.

Our work shows that today, the most dominant voices belong to legislators, legal advocates, and non-governmental organizations (NGOs) who are increasingly crowding out the agency scientists. Senators, elected politicians, like Wyoming’s John Barrasso proclaim, “The grizzly is fully recovered in Wyoming. End of story,” pushing for state control and criticizing the ESA as sluggish and outdated. Can you blame him though? Senator Barraso advocates for his Wyoming constituents who have collaborated in grizzly recovery and are now on the frontlines of human-wildlife conflict issues where grizzlies might harm livestock or tourists. All the while, population targets set by the ESA have been met, and the species remains listed.

Meanwhile, NGOs and their attorneys, such as the well-known environmental advocacy group Earthjustice, argue that delisting is premature, citing ‘political pressure’ overriding ‘biological evidence.’ The courts, too, have flexed their muscle, with rulings hinging on genetic connectivity’s role in population recovery. Ranchers with increasing grizzly conflict see these scientific developments as intentional delays to delisting rather than advancements in the field of conservation. There are no easy answers.

Wildlife management turned politics

This conflict reveals a stark reality: wildlife management is no longer just about science, it's about who dominates the political discourse, and the power that accompanies it. Legislators see delisting as a way to reclaim state authority from what they consider federal overreach. Their rhetoric, steeped in populist appeals to the Western ranching community, frames grizzlies as a recovered species with bureaucrats in Washington stalling the process of handing management back over to the states.

Montana Senator Steve Daines, for instance, highlights ‘skyrocketing’ livestock losses and bears roaming beyond their historic range. These issues resonate with rural constituents tired of federal wildlife law superseding local management by trusted state agencies. On the other hand, NGOs and legal advocates rely on the courts to maintain federal oversight, warning that state management could unleash ‘trigger-happy’ hunting seasons and jeopardize long-term survival. These advocates argue that we are facing a generational extinction crisis, where every decision we make about imperiled species could approach extinction, a route that we cannot come back from. The public, caught in the middle, may be unaware that conversations over wildlife protection have shifted from credentialed agency biologists and scientists over to politicians.

Our data underscore this shift in power. While executive branch officials, with whom scientific expertise resides, once dominated the discourse (eg fish and wildlife agency personnel at the federal and state level), they are no longer the leading voices in ESA recovery conversations. Elected politicians now lead the charge. Their influence is growing threefold over time compared to scientific agency voices. Legal advocates and NGOs, meanwhile, are shaping the debate over wildlife science with their roles amplified by lawsuits that keep grizzlies listed. Even tribes, historically sidelined, find their strongest platform in court, a sign that political systems still fail to integrate Indigenous perspectives outside litigation.

What’s lost in this debate is the ESA’s original intent: a science-driven process to recover species and then allow federal agency experts to step back so that states, who may better represent local interests, can manage species.

The path forward

This politicization threatens the ESA’s future. When politicians outshout scientists, when courts dictate biology or delay timely management responses, and when recovery becomes a bargaining chip, the law risks losing its credibility with the public. The grizzly saga suggests a path forward: agencies must adapt to this political reality, not retreat from it. Scientists can’t afford to ‘stay out of politics’ when protected species like grizzlies are lightning rods for political debate. Multi-stakeholder groups, like the Interagency Grizzly Bear Committee, offer a model bridging agencies, states, tribes, and NGOs to tackle thorny issues like genetics collaboratively rather than through unending lawsuits in the courts.

The grizzly bear’s fate isn’t just about one species: this pattern is playing out across a range of species in the West and beyond. It will prove itself as the greatest challenge for wildlife managers in an era of increased polarization. If the ESA is to endure another 50 years, it must evolve beyond a scientific ideal into a framework that navigates the messy, human politics of conservation. Otherwise, the grizzly’s roar will be drowned out by an even greater sound: the chaos of our own imperfect politics.

---

Journal

Frontiers in Conservation Science

DOI

10.3389/fcosc.2025.1508158 

 

Wolves make a rapid recovery in Europe

 

Peer-Reviewed Publication

PLOS

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Wolf on agricultural plains in northern Greece

view more 

Credit: Seryios Papaioannou, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

 Wolf populations in Europe increased by nearly 60% in a decade, according to a study led by Cecilia Di Bernardi and Guillaume Chapron at the Swedish University of Agricultural Sciences, published in the open-access journal PLOS Sustainability and Transformation.

Large carnivore populations are declining worldwide. However, in Europe, conservation policies have supported the recovery of wolves (Canis lupus) in recent decades. To understand current trends in their populations, researchers collated data on wolf numbers in 34 countries across Europe. They found that by 2022, at least 21,500 wolves lived in Europe — an increase of 58% compared to the estimated population of 12,000 a decade earlier. In most countries analyzed, wolf populations were increasing, with only three countries reporting declines over the previous decade. The researchers also investigated sources of conflict between humans and wolves, such as livestock deaths. They estimated that in the European Union, wolves killed 56,000 domestic animals per year, out of a total population of 279 million livestock. Although the risk varied between countries, on average, livestock faced a 0.02% chance of being killed by wolves each year. Compensating farmers for these losses cost European countries 17 million euros annually. Still, wolves can also have positive economic impacts, such as reducing traffic accidents and damage to forestry plantations by controlling wild deer populations. However, there wasn’t enough data available to quantify these benefits.

Considering Europe’s large human population and the widespread alteration of landscapes for agriculture, industry and urbanization, the rapid recovery of wolves over the last decade highlights their extraordinary adaptability. However, as conservationists transition from saving endangered populations to sustaining a successful recovery, the challenge will be to adapt national and international policies to ensure that humans and wolves can coexist sustainably in the long term, the authors say. 

The authors add: “The recovery of wolves across human-dominated landscapes of Europe has been continuing during the past decade, with their population growing to over 21,500 individuals by 2022 – a 58% increase in a decade. Ongoing and future challenges include damages directly caused by wolves and broader socio-political issues.”

The freely available article in PLOS Sustainability and Transformation:  https://plos.io/41wNLjq

Yellowstone wolves and other carnivores drive strong trophic cascade

 

Peer-Reviewed Publication

Conservation Biology Institute

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Downstream view of the East Fork of Blacktail Deer Creek in 2004 and 2021, northern range of Yellowstone National Park, USA.

view more 

Credit: R.L. Beschta

Corvallis, OR — February 6, 2025 — A new study reveals the profound ecological effects of wolves and other large carnivores in Yellowstone National Park, showcasing the cascading effects predators can have on ecosystems. In Yellowstone, this involves wolves and other large carnivores, elk, and willows. The research, which utilized previously published data from 25 riparian (streamside) sites and collected over a 20 year period, from 2001 to 2020, revealed a remarkable 1,500% increase in willow crown volume along riparian zones in northern Yellowstone National Park, driven by the effects on elk due to a restored large carnivore guild following the reintroduction of wolves in 1995–96, and other factors. The study was led by Dr. William J. Ripple of Oregon State University and the Conservation Biology Institute in Corvallis, OR, and published today in Global Ecology and Conservation.

Trophic cascades, the effects of predators on herbivores and plants, have long been a topic of ecological interest. The study quantifies the strength of this phenomenon for the first time using willow crown volume as a proxy for aboveground biomass, demonstrating a significant three-dimensional recovery of riparian vegetation represented by the growth in both crown area and height of established willows. The strength of the Yellowstone trophic cascade observed in this study surpasses 82% of strengths presented in a synthesis of global trophic cascade studies, underscoring the strength of Yellowstone’s willow recovery process. The authors note that there is considerable variability in the degree of recovery and not all sites are recovering.

Even though riparian areas in the western United States comprise a small portion of the landscape, the study has particular relevance since these areas provide important food resources and habitat for more wildlife species than any other habitat type. These areas also connect upland and aquatic ecosystems and are widely known for their high diversity in species composition, structure, and productivity.

“Our findings emphasize the power of predators as ecosystem architects,” said William Ripple. “The restoration of wolves and other large predators has transformed parts of Yellowstone, benefiting not only willows but other woody species such as aspen, alder, and berry-producing shrubs. It’s a compelling reminder of how predators, prey, and plants are interconnected in nature.”

Wolves were eradicated and cougars driven to low numbers from Yellowstone National Park by the 1920s. Browsing by elk soon increased, severely damaging the park’s woody vegetation, especially in riparian areas. Similar effects were seen in places like Olympic National Park in Washington, and Banff and Jasper National Parks in Canada after wolves were lost. While it’s well understood that removing predators can harm ecosystems, less is known about how strongly woody plants and ecosystems recover when predators are restored. Yellowstone offers a rare opportunity to study this effect since few studies worldwide have quantified how much plant life rebounds after large carnivores are restored.

“Our analysis of a long-term data set simply confirmed that ecosystem recovery takes time. In the early years of this trophic cascade, plants were only beginning to grow taller after decades of suppression by elk. But the strength of this recovery, as shown by the dramatic increases in willow crown volume, became increasingly apparent in subsequent years,” said Dr. Robert Beschta, an emeritus professor at Oregon State University. “These improving conditions have created vital habitats for birds and other species, while also enhancing other stream-side conditions.”

The research points to the utility of using crown volume of stream-side shrubs as a key metric for evaluating trophic cascade strength, potentially advancing methods for riparian studies in other locations. It also contextualizes the value of predator restoration in fostering biodiversity and ecosystem resilience.

Protected areas provide habitat for threatened lynx, but wildfire poses risks

Future wildfire may be the greatest threat to lynx habitat in the southern Rocky Mountains

Peer-Reviewed Publication

USDA Forest Service - Rocky Mountain Research Station

 

image: 

A lynx prowls through thick snow with trees in the background. USDA Forest Service Rocky Mountain Research Station-Canada Lynx of the Rockies Research Program. 

view more 

Credit: John Squires USDA Forest Service Rocky Mountain Research Station-Canada Lynx of the Rockies Research Program.

FORT COLLINS, Colo., January 6, 2025 — Canada lynx are specialized hunters, able to travel in deep snow and spot prey in the darkness from 250 feet away. Keen hearing and vision make them excellent trackers, but what do we learn by turning the tables and tracking them? Scientists are using GPS data and advanced modeling to refine maps and identify important habitat characteristics, particularly in the forests of western Colorado, southern Wyoming, and northern New Mexico, the southernmost extent of its range.

New research and updated maps show that more than half of lynx habitat in the southern Rocky Mountains overlaps protected areas like wilderness and national parks. The maps also show that lynx habitat is sparse, patchy, and poorly connected, existing only in narrow bands due to Colorado’s complex mountainous terrain. These maps can identify corridors where habitat loss affects animal movement, which is important for healthy populations. Updated maps help managers focus conservation efforts and pinpoint places to promote new habitat, especially given the frequency of human development, fire, and forest insect outbreaks near the edges of lynx range.

Lynx in the western US prefer high elevation spruce-fir forests with tree branches hanging close to the snow or ground surface, providing dense horizontal cover. This forest structure supports the cat’s favorite prey, snowshoe hares, which can make up 90 percent of their diet in winter. Lynx were reintroduced to the southern Rockies over two decades ago, after populations had fallen below a self-sustaining level. Several generations of females and kittens have successfully established here, allowing these populations to bounce back.

Researchers used GPS collars to track lynx within the study area, focused on the southern extent of its range. They also considered over 40 habitat or environmental characteristics, such as the amount of precipitation as snow versus rain, the month with the coldest temperature, road density, vegetation, and slope position. Combining GPS and habitat data and using state-of-the-art statistical tools and modeling methods, these scientists identified which characteristics best predicted where lynx were found and used this information to map “likely” lynx habitat where cats have a high probability of living, breeding, and successfully raising young.

Then they took this information one step further, comparing “likely” habitat with disturbances like insect outbreaks, wildfire, timber harvest, or human-footprint impacts such as urbanization or ski resorts. The scientists found that around one-third of likely habitat overlapped with disturbance, including forest insect outbreaks (31 percent), wildfire (5 percent), and forest management activities like tree harvest and prescribed burning (3 percent). Despite the greater overlap of lynx habitat with insect outbreaks, the scientists are more concerned by the impacts of severe wildfires.

“We know that lynx continue to occupy areas after insects kill the overstory trees during spruce-beetle outbreaks. Forests impacted by spruce beetles still have enough young conifer trees in the understory to support hares,” said Dr. John Squires, the study's principal investigator and a Rocky Mountain Research Station research wildlife biologist. “Also, some tree species like subalpine fir often survive spruce beetle attacks. That means that forest insects represent a more benign threat to lynx compared to broad-scale, high-severity wildfire.”

The researchers found that lynx tend to avoid fire-impacted areas until the understory has regrown–a process that takes upwards of 50 years in subalpine forests in the southern Rockies, where fires tend to burn less frequently than lower elevation forests and are often stand-replacing.

“Although fire disturbance from 1990-2022 overlapped only 5 percent of likely lynx habitat in this area, we believe that frequent, high-severity fire is the main risk to lynx in high-elevation forests moving forward,” continued Squires.

“We were surprised at how little lynx habitat overlapped areas of managed forest and human development,” said Dr. Lucretia Olson, study coauthor and a Rocky Mountain Research Station ecologist. “While forest management mainly causes temporary habitat changes, activities like urbanization and developing or expanding ski areas often lead to permanent losses. We hope our work will reach managers who make complex decisions about land uses.”

Squires stressed the value of partnerships for conducting this research: “Close collaboration across state and federal agencies in terms of data sharing, logistical support, and added expertise made this research possible.”

Authors of this research include John Squires and Lucretia Olson of the Forest Service Rocky Mountain Research Station, Jacob Ivan of Colorado Parks and Wildlife, Peter McDonald of the Forest Service Rocky Mountain Region, and Joseph Holbrook of the University of Wyoming. For more information about this research, please refer to the scientific publication or visit the webpage for the Canada Lynx of the Rockies Research Program.

---

Journal

Biodiversity and Conservation

DOI

10.1007/s10531-024-02978-8 

Conserving high-elevation grasslands in Peru is key to protect Andean bears

 

Bears forage for young bromeliad plants in Peru’s puna grasslands, but prefer to avoid cattle

Peer-Reviewed Publication

PLOS

 

image: 

Examples of foraging sign left by Andean bears on terrestrial bromeliads in Peru. Clockwise from the top right: (a) juvenile Andean bear consuming a bromeliad at a camera station inside MNP; (b) characteristic observation of a vegetative P. leptostachya foraged by Andean bear; (c) a close up of the basal meristematic tissue that Andean bears feed on.

view more 

Credit: Pilfold et al., 2024, PLOS ONE, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

Andean bears carefully select the best foraging locations and plants to maximize nutrition and avoid livestock, according to a study publishing December 18, 2024, in the open-access journal PLOS ONE by Nicholas Pilfold at the San Diego Zoo Wildlife Alliance in California, U.S., and colleagues.

Andean bears, also known as ‘spectacled bears’ because of the white markings encircling their eyes, are endemic to the Andes. They are listed as vulnerable by the IUCN and are threatened by habitat loss, climate change, and conflict with humans. Flowering plants called bromeliads form a major part of their diet, but little is known about their foraging behavior and feeding preferences across the mixture of cloud forest and grassland habitats within their range.

Researchers conducted surveys of two species of bromeliad (Puya leptostachya and Puya membranacea) in high-altitude grasslands, called ‘puna’, in and around Manu National Park in Peru. They recorded the location of each plant and whether there was evidence of consumption by Andean bears (Tremarctos ornatus), through observations of dug up, partially eaten stalks, a characteristic feeding sign of the bears.

Trail cameras confirmed that Andean bears were present at the survey locations. However, the surveys showed that the bears were foraging in just 16.7% of available bromeliad patches. Andean bears were more likely to forage for bromeliads in the dry season when there were young, tender plants available, which are likely easier for them to digest and more nutritious. The bears preferred to eat P. leptostachya plants growing on east-facing, steep slopes of puna grassland at the forest’s edge. They rarely foraged for bromeliads outside the national park, where livestock like cattle are grazed.

The results suggest that Andean bears actively seek out bromeliads in locations where they feel safe from human disturbance. Although the bears avoided areas with livestock, they foraged in locations that had been grazed by livestock only a few decades ago. This behavioral flexibility may help them to regain lost territory quickly with help from targeted conservation measures. High-altitude grasslands bordering cloud forest are key habitats for Andean bears and conservation managers should consider how livestock impact this important ecosystem, the authors say.

The authors add: “Using the largest collection ever of field data on the feeding behavior of Andean bears in high elevation grasslands, we found that the bears actively selected for specific food resources within the grasslands, indicating that these areas are of nutritional importance to the bears. We also found Andean bears strongly avoided areas with livestock impacts to the grasslands, but that the cessation of livestock keeping restored the grasslands into areas Andean bears prefer within a short timeframe.”

The freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0314547