The Daily Bucket is a nature refuge. We amicably discuss animals, weather, climate, soil, plants, waters and note life’s patterns.
We invite you to note what you are seeing around you in your own part of the world, and to share your observations in the comments below.
|
.
The Beaverhead Mountains are an imposing chain of snowy peaks on the Idaho-Montana divide with several 10,000-ft crests punctuating the skyline. In the middle of winter, my thoughts train on these alpine peaks knowing that deep within their recesses, a female wolverine is about to give birth to her litter of 1-3 kits. Her natal den is snug within a tangle of snow-covered fallen trees and boulder talus near timberline. The den and its branching snow tunnels are blanketed by 3-15 feet of snowdrift, creating an insulated and safe haven for mother and young. The snowdrift will last late into spring, about the time her kits are weaned and ready to follow her to high mountain hunting grounds.
Few species live so close to the knife-edge of existence as the wolverine. Navigating a world of avalanches and blizzards, scavenging the remains of wolf kills, patrolling enormous territories to find mates and sufficient food, wolverines are hard-wired for extreme living. Their “unmitigated badass behavior”* is not just the stuff of hyperbolic legend or the inspiration for a superhero with anger management issues; it is empirical fact, straight from wolverine researchers themselves:
If wolverines have a strategy, it’s this: Go hard, and high, and steep, and never back down, not even from the biggest grizzly, and least of all from a mountain. Climb everything: trees, cliffs, avalanche chutes, summits. Eat everybody: alive, dead, long-dead, moose, mouse, fox, frog, its still warm heart or frozen bones.
~ Doug Chadwick* The Wolverine Way
Yet despite tough and tenacious reputations, wolverines in the lower 48 states are increasingly being pushed closer to the edge by multiple human pressures, including development, trapping, winter recreation, and above all, by a warming climate. Since 1994, the species has had a long and difficult history with the Endangered Species Act (ESA). Currently, wolverines in the contiguous U.S. are proposed for listing as a threatened species under the ESA due to the primary threat of habitat and range loss attributed to climate change.
WILD AS THE SNOW-CAPPED LANDSCAPES THEY INHABIT
The largest terrestrial member of the weasel family (Mustelidae), wolverines resemble a small bear with short legs, large snowshoe-like feet, and heavy musculature of the head, neck, and shoulders — adaptations that allow it to travel on snow and find and feed on frozen carrion. Their dense, frost-resistant fur is dark-brown with buff-colored lateral stripes along the flanks, with a silvery or “grizzled” face mask distinct in some individuals. The pelage of throats and chest are light-colored with patterns unique to individuals. Typical of weasels, wolverines have well-developed anal musk glands used for scent-marking. Males weigh 24-40 pounds and are typically 30-40% larger than females.
Wolverines have a circumboreal distribution across tundra and boreal coniferous forest zones of North America and Eurasia in areas where cold, snowy conditions exist for much of the year. In North America, a peninsula of wolverine distribution dips southward into the U.S. Rocky Mountains and Cascade Range. An estimated 250-300 wolverines currently occupy a patchy network of alpine and subalpine habitats in western Montana, central and northern Idaho, northwest Wyoming, north-central Washington, and northeast Oregon. Present day distribution represents a significant retraction from historical distribution (pre-1920s), which once encompassed the Sierra Nevada and southern Rockies. Reasons for this range retraction are poorly understood, but broad-scale predator control programs are implicated.
A SNOW-DEPENDENT SPECIES STANDING SQUARELY IN THE PATH OF CLIMATE CHANGE
What might be the fate of the wolverine if the two commodities it depends on—cold and snow—diminish in the coming decades due to a warming climate? To understand how the complexities of climate change may affect wolverines, it is important to understand the basic biology of the species. The wolverine is unique among mammals in that it is heavily dependent on spring snowpack for successful reproduction. Female wolverines dig elaborate birthing dens in the highest elevations of their territories, tunneling 5-16 feet deep into the snowpack to keep their litter secure from predators and insulated from frigid temperatures. Females may move the nursing kits to secondary dens, keeping litters hidden under snow cover to 9-10 weeks of age. Dens are abandoned in April/May when snowmelt begins to accumulate in dens, about the time kits are weaned. Habitat that loses these essential snowpack features due to climate warming may limit wolverine distribution via decreased kit survival.
In the lower 48 states, wolverines appear to select habitats that avoid high summer temperatures (≥72° F in August). Wolverines have a slightly higher metabolic rate than other mammals their size, which keeps their internal furnace stoked a little hotter. Their luxuriant, dense coat helps to hold their heat while it repels any heat-sapping moisture. The same adaptations that help wolverines contend with cold, snowy conditions become liabilities in a warming climate. At the southern extent of their U.S. range, some currently occupied wolverine habitats may be pushed beyond this summer temperature threshold, forcing wolverines to retreat further upslope or to more northerly latitudes.
Wolverine researchers theorize that wolverines take advantage of a cold, low-productivity niche by caching food in snowbanks and boulder fields to refrigerate carrion and freshly killed prey. If temperatures warm and snow duration and cover decrease, cached food would be more susceptible to spoilage, thereby requiring wolverines to expend precious metabolic energy searching for food.
Based on research that correlated wolverine distribution with spring snow persistence and low summer temperatures, climate change projections suggest that wolverine habitat will shrink and become more highly fragmented with increased warming. A 67% loss of wolverine habitat is predicted in the western U.S. by 2059 due to loss of snowpack. In addition to reducing the number of wolverines that can be supported by shrinking habitat patches, increased fragmentation and loss of intervening dispersal habitat may impact genetic exchange among wolverine subpopulations, threatening remaining subpopulations with inbreeding and localized extinctions.
Maintaining connectivity across the vast geographic scale of the western U.S. is critical for the long-term survival of wolverines, but is an area where wolverines are inherently vulnerable. Successful wolverine dispersal is directly linked to pathways with persistent spring snow cover. Climate change resulting in reduced snow pack and snow duration signals a future loss of connectivity corridors for wolverines.
Another factor impacting wolverine connectivity is increasing human development. In dispersing from one habitat island to the next, wolverines must often navigate through significant blocks of private land networked with roads, rural housing developments, and associated infrastructure. Growth projections for the Inland West are among the highest in the nation and will continue to drive development in dispersal corridors. Although the threshold of development triggering reduced survival and gene flow of wolverines is unknown, the mechanisms by which wolverine may be impacted (road-kill, reduced permeability) are known. Just a few years ago, a female wolverine was hit and killed by a vehicle on a U.S. highway in east-central Idaho. In June 2018, a male wolverine was struck and killed on I-90 west of Snoqualmie Pass in Washington.
Trapping of wolverines is currently prohibited in the lower 48 states; however, trappers setting traps for other legal furbearers do incidentally capture wolverines, though purportedly in very low numbers. In Idaho, where 14 incidentally-trapped wolverines were reported from 1965-2014, about half were live releases. Those that died were captured in highly lethal traps, such as conibears (body-gripping traps). I am directly aware of another female wolverine killed in Idaho last winter in a snare intended to capture red fox. In “island habitats” such as the Beaverhead Mountains, trappers have access to large areas of front country to set traplines for coyote, bobcat, or wolves. Often, this front county is deer and elk winter range. Wolverines will readily head downhill to scavenge winter-killed deer and elk, putting them at risk of encountering traps or snares. If snow pack or snow season diminishes with climate warming as predicted, trappers will be able to infiltrate further into wolverine habitat, increasing the risk of injury or death to wolverines venturing into traps set for other furbearers.
The remote and rugged habitats of the wolverine were once isolated from human activity and largely undisturbed in winter months. In many areas of the West, winter backcountry recreation continues to grow in popularity, bringing advancements in mechanized access options (snowmachines, snowcat-skiing, heli-skiing) that expand winter recreation into previously unreachable terrain. Many winter recreation sites spatially overlap with areas occupied by wolverines, prompting concerns about the effects of winter recreation on wolverines, particular denning females.
GROUND-BREAKING WOLVERINE RESEARCH
Over the winters of 2010-2015, a project partnership led by Dr. Kimberly Heinemeyer of Round River Conservation Studies conducted the Wolverine-Winter Recreation Study to: 1) increase the science-based understanding of the effects of winter recreation on wolverine populations through examining wolverine behaviors, habitat use, and reproductive efforts within landscapes supporting a diversity of winter recreation activities; and 2) provide science-based information to guide public land management for the sustainability of both winter recreation and wolverine. The study found that wolverines responded negatively to increasing intensity of winter recreation, with off-road or dispersed recreation producing a stronger response than recreation concentrated on access routes (e.g., cross-country ski trail or snowmobile trail). The study also advised that significant habitat degradation to reproductive females during denning season should be a concern in landscapes with high levels of winter recreation. One of the study’s more important findings:
We speculate that the potential for backcountry winter recreation to affect wolverines may increase under climate change due to reduced snow pack and snow season that may concentrate winter recreationists spatially and temporally in these high elevation habitats during a season when these species face increased energetic stressors and females enter reproductive dens.
This study provides land management agency personnel (i.e., U.S. Forest Service) with more detailed understanding of important habitat characteristics within wolverine home ranges to help them address potential conflicts between recreation and wolverines in the large landscapes they manage.
Conducted over two winters in 2017 and 2018, the Western States Wolverine Conservation Project was an unprecedented, ambitious baseline survey for wolverine occupancy across the four states where the species currently occurs – Montana, Idaho, Washington, and Wyoming. The study was ‘unprecedented’ in its level of collaboration, funding, and geographic/jurisdictional scale, and in providing the first estimate of wolverine distribution and occupancy across the lower 48 from which future monitoring could be compared. It was ‘ambitious’ in its approach, requiring survey crews to access deep into mountain ranges to set up camera/bait stations equipped to gather hair samples for DNA analysis. The survey used a grid of 15 x 15 kilometer cells with >50% modelled wolverine habitat as sampling units, identifying 633 cells as potential habitat. A sample of 183 cells was then randomly selected for survey using a standard protocol across all four states. A single camera & bait/lure station was deployed in each cell from November through March over two consecutive winters.
The survey detected wolverines in 59 of the 183 (11%) cells that were sampled. After analyzing the findings, and accounting for “imperfect detectability,” the research team concluded that wolverines were likely present in roughly half of the 633 cells across the four states. The survey not only confirmed broad distribution of wolverines across the region, it also showed that recolonization has substantially progressed since historical lows in the early to mid-1900s. The survey identified a few “hotbeds” of wolverine activity, including the Bob Marshall Wilderness and central Idaho’s Sawtooth Mountains, and several areas previously thought to be unoccupied, such as central Montana’s Little Belt Mountains and Wyoming’s Gros Ventre Mountains and Wind River Range. Hair samples collected will allow studies into a variety of genetic-based questions, including identification of areas important for connectivity. The four states have agreed to repeat the survey every five years to determine if wolverine populations are stable, increasing, or decreasing. They’re also in discussions about possibly translocating wolverines to new areas of suitable habitat in Colorado and California, which could increase the population as much as 50% in the lower 48.
Though uncertainties about the effects of climate change on wolverines prevail, it behooves wildlife and land managers, researchers and conservationists, to prepare for future scenarios. For wolverines in the contiguous U.S., one of the most effective conservation strategies is to identify, protect, and manage secure linkage habitat between high elevation ecosystems to ensure that this far-roaming species can navigate freely and safely across the landscape. And while wolverines may coexist with some level of human disturbance and habitat modification, strategies that avoid or minimize impacts of human development, winter recreation, and incidental trapping will put less stress on this species already living at the edge. The pending ESA listing decision will be the culmination of years of research and conservation work by dedicated scientists, managers, and concerned citizens. With the growing challenge of climate change, the continuing work of this collaborative will be ever more important to avert the loss of wolverine in a warming world.
What Can You Do to Conserve Wolverines?
1. Support public policies that advocate for keeping global warming to less than 1.5 degree C above pre-industrial levels as recommended by the Intergovernmental Panel on Climate Change through accelerated fossil fuel retirement.
2. Continue to voice your concerns to your state and federal representatives about Trump Administration proposed changes to the ESA that limit the extent to which climate change impacts can serve as a basis for listing decisions and critical habitat designations.
3. Keep our public lands in public hands.
4. Monitor land use and planning & zoning proposals in states occupied by wolverines and advocate for creating and protecting effective connectivity corridors for wide-ranging wildlife species such as wolverine, fisher, grizzly bear, gray wolf, and Canada lynx.
4. Support landowner incentive programs (e.g., conservation easements) to encourage voluntary landowner engagement in conserving connectivity corridors.
6. Monitor and comment on state trapping regulations to ensure they do not impact wolverines and other protected wildlife.
7. Advocate for secure habitats for wolverines on public lands and proper multiple use management (e.g., winter recreation, ski area developments) to avoid or minimize negative impacts to wolverines.
8. Contribute $ to state Nongame, Wildlife Diversity, or Natural Heritage programs for the management of wolverines. Most are desperately underfunded and do not receive taxpayer support.
9. Support The Wolverine Foundation, a non-profit organization promoting science-based management of wolverines across their global range.
🍂
What’s up in nature in your area today?
💨
SPOTLIGHT ON GREEN NEWS & VIEWS
EVERY SATURDAY AT 3 P.M. PACIFIC TIME
DON’T FORGET TO VIEW METEOR BLADE’S COLLECTION OF LINKS AND EXCERPTS FROM ENVIRONMENTALLY ORIENTED POSTS PUBLISHED ON DAILY KOS DURING THE PREVIOUS WEEK
|