Study: Wolverines need refrigerators

Will insects and bacteria consume more of the wolverine's food if the climate warms?

Wolverines live in harsh conditions; they range over large areas of cold mountainous low-productivity habitat with persistent snow. The paper suggests wolverines take advantage of the crevices and boulders of the mountainous terrain, as well as the snow cover to cache and "refrigerate" food sources such as elk, caribou, moose and mountain goat carrion, ground squirrels and other food collected during more plentiful times of year. These cold, structured chambers provide protection of the food supply from scavengers, insects and bacteria. In addition, the refrigerated caches increase the predictability of available food resources, reduce the energy spent by females searching for food while in lactation phase, and decrease the time mothers spend away from cubs.

The paper appears in the current edition of the Journal of Mammalogy and was co-authored by Robert M. Inman of WCS, Audrey J. Magoun of Wildlife Research and Management, Jens Persson of the Swedish University of Agricultural Sciences, and Jenny Mattisson of the Norwegian Institute for Nature Research.

"People don't normally think of insects and microbes as being in competition for food with wolverines," said lead author Robert Inman of the Wildlife Conservation Society's North America Program. "But in fact, bacteria will devour an unprotected food source if that source is available."

Through an extensive literary review, the authors noted that wolverine reproduction is confined to a brief period of the year, and the lactation phase in females (February through April) corresponds to a period of low availability of food resources. Wolverines, which are opportunistic foragers, have adapted by amassing food caches during the preceding winter months when food is more readily available. Without the cached food supply or an unforeseen alternative (such as a winter-killed ungulate), early litter loss occurs.

Inman said, "Understanding why and how wolverines exist where they do and the various adaptations they have evolved to eke out a living will better inform population management strategies and conservation of the species."

Climate change will play a key role in management planning for the conservation of wolverines, the authors say.

In a study published in 2010, wolverine biologists demonstrated a relationship between the areas where wolverines exist (their distribution) and persistent snow cover. The first theory advanced was that wolverines must have deep snow available in springtime so that they can give birth to their small cubs in a warm, secure den. The newly released study suggests that other factors related to climate and snow pack, such as competition for food, may also be involved in explaining the limits to wolverine distribution.

Because of their dependence on snow pack, wolverines were recently listed as warranted for protection under the Endangered Species Act due in large part to the threat of climate change reducing distribution and habitat connectivity. The authors say that a deeper understanding of how and why wolverines use snow pack the ways they do is critical to understanding how climate change will impact survival and reproductive rates.

"Shedding light on the specific mechanism of how climate will affect wolverines is important in order to know what to do to help them hold on," said WCS's North America Program Director, Jodi Hilty.

Inman and co-authors published a study in December of 2011 on the spatial ecology of wolverines in the Journal of Wildlife Management. This latest paper represents the second of several that will help to inform a conservation strategy for the species.

The Iberian wolf lives close to humans more for refuge than for prey

The Iberian wolf lives in increasingly humanised landscapes, with limited food resources and its presence is not always welcome. But, according to Spanish researchers, food availability plays a secondary role compared to landscape characteristics, which can offer refuge and allow wolves to remain in human-dominated environments in Galicia.

The habitat of the Iberian wolf (Canis lupus signatus) varies greatly across the Iberian Peninsula and its diet revolves around what is available, ranging from wild animals to domestic waste. In contrast, this predator is able to survive in humanised landscapes where characteristics provide them refuge from humans.

"Although the wolf boasts highly adaptable strategies for survival, landscape is the factor we have analysed that best explains their distribution across Galicia," as explained to SINC by Luis Llaneza, researcher at Asesores en Recursos Naturales (A.RE.NA.) and lead author of the study published in the 'Diversity and Distributions' journal.

His research has allowed for the analysis of the relative influence of landscape attributes, human presence and food resources and the existence of wolves over an area of 30.000 km2 in the north-west of the Peninsula.

The scientists concentrated on indirect signs of the animal to identify their distribution in Galicia. In total, 1,594 excrement samples were analysed, which were then verified using DNA molecular analysis to locate them in the territory.

The results revealed that landscape properties are decisive in terms of animal safety at a level of 48%, whereas the presence of humans (buildings and roads) is influential at a level of 35% and food availability as 17%. Llaneza says that "as long as tolerated by humans, the wolf can be found in any place where there is refuge and food."

According to the scientists' model, the presence of wolves would increase if there were more semi-wild horses and wild ungulates. As the authors outline, "the amount of semi-wild horses in Galicia could be a key factor determining the presence of wolves in areas where wild prey or other food sources area not so abundant."

A safe refuge for the wolf

After studying the effect of altitude, land orography and refuge availability, researchers demonstrated that these mammals require their habitat to be a plant mosaic containing vegetation of more than 50 centimetres in height (bushes and shrubs) to hide in.

"These animals remain in Spain and little by little we are beginning to understand how they survive in human-dominated areas," says Llaneza. The study reveals that wolves choose high places that are difficult to access, such as areas where vegetation provides refuge from humans.

"The density of vegetation allows wolves to go unnoticed by humans", adds the researcher, who recalls that humans are the known cause of wolf death in 91% of instances. Some 65% of wolves are killed on the road, 20% by poaching and 6% by legal hunting.

With the participation of the University of Santiago de Compostela and the Doñana Biological Station (EBD-CSIC), the research team concludes that a set of variables and data analysed explains only 20% of wolf distribution in Galicia. Their next undertaking will be the study of other factors that influence wolf survival in humanised areas, such as the extent to which they are tolerated.

Cougars are re-populating their historical range

American mountain lions, or cougars, are re-emerging in areas of the United States, reversing 100 years of decline. The evidence, published in The Journal of Wildlife Management, raises new conservation questions, such as how humans can live alongside the returning predators.

"The cougar population declined dramatically from 1900, due to both hunting, and a lack of prey, leaving the remaining population isolated to the American west," said Michelle LaRue from the University of Minnesota. "Here we present the hard evidence that the western population has spread, with cougar populations re-establishing across the Midwest."

Three main cougar populations exist in the Midwest centered around The Black Hills in South Dakota, however, cougars are venturing far outside of this range. One male cougar from the Black Hills was found to have traveled 2,900 kilometers through Minnesota, Wisconsin and New York, before ending up in Connecticut.

"While the distance the Connecticut cougar traveled was rare, we found that cougars are roaming long distances and are moving back into portions of their historical range across the Midwest ", said LaRue. "Our study took in over 3,200,000 Km_ of territory, confirming the presence of Cougars from Texas, Arkansas and Nebraska, to the Canadian provinces of Ontario and Manitoba."

Working alongside scientists from Southern Illinois University Carbondale and The Cougar Network, LaRue and Principal Investigator Dr. Clay Nielsen analyzed cougar sightings which have been reported since the 1990's to characterize confirmed sightings over time, assess habitat suitability and confirm where cougar populations are being re-established.

Aside from confirmed sightings, the team's evidence included carcasses, tracks, photos, video, DNA evidence and cases of attacks on livestock across 14 states and provinces of North America. Only sightings which were verified by wildlife professionals were included, while sightings of animals known to be released from captivity were excluded to ensure only natural repopulation was analyzed.

The results reveal 178 cougar confirmations in the Midwest with the number of confirmations steadily increasing between 1990 and 2008. Approximately 62% of confirmed sightings took place within 20km of habitat that would be considered suitable for cougar populations.

When cougar carcasses were recovered 76% were found to be male. As the Connecticut example shows, males are capable of traveling long distances and this finding suggests males are leading a stepping-stone dispersal of the cougar population.

"This evidence helps to confirm that cougars are re-colonizing their historical range and reveals that sightings have increased over the past two decades," concluded LaRue. "The question now is how the public will respond after living without large carnivores for a century. We believe public awareness campaigns and conservation strategies are required across these states, such as the Mountain Lion response plans already in place in Nebraska and Missouri."

Loss of Predators in Northern Hemisphere Affecting Ecosystem Health

A survey on the loss in the Northern Hemisphere of large predators, particularly wolves, concludes that current populations of moose, deer, and other large herbivores far exceed their historic levels and are contributing to disrupted ecosystems.

The research, published recently by scientists from Oregon State University, examined 42 studies done over the past 50 years.

It found that the loss of major predators in forest ecosystems has allowed game animal populations to greatly increase, crippling the growth of young trees and reducing biodiversity. This also contributes to deforestation and results in less carbon sequestration, a potential concern with climate change.

"These issues do not just affect the United States and a few national parks," said William Ripple, an OSU professor of forestry and lead author of the study. "The data from Canada, Alaska, the Yukon, Northern Europe and Asia are all showing similar results. There's consistent evidence that large predators help keep populations of large herbivores in check, with positive effects on ecosystem health."

Densities of large mammalian herbivores were six times greater in areas without wolves, compared to those in which wolves were present, the researchers concluded. They also found that combinations of predators, such as wolves and bears, can create an important synergy for moderating the size of large herbivore populations.

"Wolves can provide food that bears scavenge, helping to maintain a healthy bear population," said Robert Beschta, a professor emeritus at OSU and co-author of the study. "The bears then often prey on young moose, deer or elk -- in Yellowstone more young elk calves are killed by bears than by wolves, coyotes and cougars combined."

In Europe, the coexistence of wolves with lynx also resulted in lower deer densities than when wolves existed alone.

In recent years, OSU researchers have helped lead efforts to understand how major predators help to reduce herbivore population levels, improve ecosystem function and even change how herbivores behave when they feel threatened by predation -- an important aspect they call the "ecology of fear."

"In systems where large predators remain, they appear to have a major role in sustaining the diversity and productivity of native plant communities, thus maintaining healthy ecosystems," said Beschta. "When the role of major predators is more fully appreciated, it may allow managers to reconsider some of their assumptions about the management of wildlife."

In Idaho and Montana, hundreds of wolves are now being killed in an attempt to reduce ranching conflicts and increase game herd levels.

The new analysis makes clear that the potential beneficial ecosystem effects of large predators is far more pervasive, over much larger areas, than has often been appreciated.

It points out how large predators can help maintain native plant communities by keeping large herbivore densities in check, allow small trees to survive and grow, reduce stream bank erosion, and contribute to the health of forests, streams, fisheries and other wildlife.

It also concludes that human hunting, due to its limited duration and impact, is not effective in preventing hyper-abundant densities of large herbivores. This is partly "because hunting by humans is often not functionally equivalent to predation by large, wide-ranging carnivores such as wolves," the researchers wrote in their report.

"More studies are necessary to understand how many wolves are needed in managed ecosystems," Ripple said. "It is likely that wolves need to be maintained at sufficient densities before we see their resulting effects on ecosystems."

"The preservation or recovery of large predators may represent an important conservation need for helping to maintain the resiliency of northern forest ecosystems," the researchers concluded, "especially in the face of a rapidly changing climate."

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Wolverine Ecology & Conservation - Yellowstone National Park

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The Northern Rockies Conservation Cooperative (NRCC) has partnered with the U.S. Forest Service, National Park Service, Yellowstone Park Foundation, and others to research wolverine ecology in Glacier & Yellowstone National Parks. These two projects lead to an increased understanding of wolverine distribution and residency, reproductive characteristics, habitat selection, food habits, connectivity of populations, and population parameters such as survival rates, birth rates, and dispersal. Additionally, public education components of these projects foster appreciation and support for wolverine conservation.

Here are excerpts from their Wolverine Conservation in Yellowstone National Park: Final Report

Wolverines in the contiguous United States are a strong concern for federal land managers and the public. The species was designated a candidate species (warranted for listing under the Endangered Species Act, but precluded by work on species of higher priority) by the US Fish and Wildlife Service in 2010. Wolverines are particularly vulnerable to extirpation due to their low numbers and large spatial requirements (Banci 1994; Copeland and Whitman 2003). Wolverine populations in the conterminous United States are small and isolated as compared to those in Canada due to naturally fragmented habitat (Aubry et al. 2007; Ruggerio et al. 2007) and infrequent exchange of individuals between mountain ranges (Cegelski et al. 2003; Kyle and Strobeck 2001, 2002). These attributes contribute to low genetic effective population sizes and low population viability (US Fish and Wildlife Service 2008). Due to its importance for the security and thermoregulation of neonates, spring snow cover may limit the wolverine’s distribution and abundance, yet this habitat component is declining across the species’ geographic range due to global climate change (Aubry et al. 2007; Copeland et al. 2010).

The wolverine is one of the least studied carnivores in North America, particularly in the contiguous United States where it occurs at the southern extent of its range (Ruggiero et al. 2007). Previous reports, surveys, and sightings records suggest that wolverines historically occurred throughout the Greater Yellowstone Ecosystem (Skinner 1927; Smith 1955; Mobley 1962; Hoak et al. 1982; Groves 1988; Consolo-Murphy and Meagher 1995; Robinson and Gehman 1998; Murphy et al. 2004).

The Wildlife Conservation Society is conducting a long-term study in the western and southern portion of the ecosystem (Inman et al. 2007a, 2008). However, little information is available concerning this species’ distribution and ecology in Yellowstone National Park and the adjoining national forests along the park’s northeast, east, and southeast boundary.

Our study objectives were to document (1) the distribution of wolverines in Yellowstone and eastern portion of the ecosystem; (2) their population characteristics, including reproduction, survival, sources of mortality, and food habits; (3) their habitat requirements, particularly those related to natal and maternal denning; and (4) their movements, including any that provide connectivity with populations in other ecosystems. To improve support for its conservation, it was also our aim to increase public awareness of this unique and mysterious carnivore (Appendix 1).

We documented wolverine distribution and population characteristics from 2005 to 2009 in Yellowstone National Park and its neighboring wilderness areas along the park’s east, northeast, and south boundaries by capturing and monitoring radio-marked individuals, and conducting surveys for their tracks during winter. We captured four individuals and collaboratively monitored three others, including two immigrants, that were previously marked by Wildlife Conservation Society biologists in the western portion of the Yellowstone ecosystem.

Wolverines in our study area selected habitats above 2,450 meters (8,000 ft), that is, in the Hudsonian (boreal) life zone, but did not use alpine habitats extensively.

Live-trapping, telemetry data, and surveys for tracks indicated that wolverine numbers and distribution were more limited than expected, despite the fact that two contemporary models estimated an extensive coverage of wolverine habitat in the area. Wolverines occurred in the Absaroka-Beartooth Wilderness along the north boundary of the park, and at the southeast corner (Thorofare region) and the adjoining Washakie and Teton Wilderness areas. When conducting helicopter-based surveys for tracks during winter, we did not detect any wolverines in the park interior, including the portion of the Gallatin Range inside the park; the Washburn and Snake River Ranges; the Central and Madison Plateaus; and the Bechler region. We also did not detect resident wolverines in the North Absaroka Wilderness and the adjoining areas along the east boundary, including the upper Lamar River. Surveys for ungulates in this area during the winter did not indicate that the availability of carrion significantly limited wolverine numbers and distribution, although our anecdotal observations suggested that winter food might be limited in the heavily forested portions of interior Yellowstone.

Wolverine home ranges did not overlap, and radio-marked individuals did not make extra-home range movements to forage in the major ungulate winter ranges in and near our study area, including the Pelican and Hayden Valleys, and the northern winter range. Our limited demographic data suggested that reproductive rates of wolverines were low, that home ranges were large, and that rates of survival were similar to estimates for other populations in the conterminous United States. The dynamics and distribution of our population appeared to be strongly linked to ingress from well-established populations in other parts of the ecosystem, rather than to recruitment of offspring born to our resident females.

We developed and tested a reliable method to rapidly assess wolverine distribution over large areas using helicopter-based searches for tracks during the winter. We were highly successful in finding tracks of resident, radio-marked wolverines during both preliminary tests (searches in 10 x 10 km survey [grid] cells) on a Wildlife Conservation Society study site, and when applying our refined technique to wolverines on our study area. This survey method can be broadly applied to the incised terrain typical of the Rocky Mountains as a first step in assessing wolverine populations, provided that surveys are adequately replicated. We recommend that biologists continue to investigate the factors that limit the growth of wolverine populations, particularly in areas such as ours where models suggest that suitable habitat is abundant.

Rare Wolverine Photographed in Montana

The Wildlife Conservation Society recently released this camera-trap photo of a wolverine retrieving bait placed in a tree in Montana.

The frame upon which the animal climbs is designed so that the unique markings on the underside of the wolverine are revealed to the motion-sensing camera.

Scientists use these markings to identify individual animals and document their distribution and range.

WCS’s eight-year study of wolverines in the Greater Yellowstone Ecosystem has led to a better understanding of wolverine ecology and will help inform conservation strategies so that this rare species can survive despite the 21st century conservation challenges it faces. An estimated 250-300 wolverines remain in the “lower 48,” where they occupy about half of their former range in high alpine peaks of the western United States.

Oregon's lone wolf pack threatened

Journey, an intrepid gray wolf from Oregon's lone wolf pack, made history last year when he traveled more than 1000 miles to become the first wolf in California in nearly a century.

Now Journey's family, the Imnaha pack, is under attack again at home, this time by the Oregon Cattleman's Association, which is pushing a law that would allow for the annihilation of the pack.

Here's why:

A pack of wolves roaming grasslands in Eastern Oregon killed another cow over the weekend.

The Oregon Department of Fish and Wildlife said a yearling heifer was found dead on a ranch east of Joseph in Wallowa County. ODFW officials said the rancher had coraled his 700 cattle Sunday night in a pasture near his home and that the wolves broke in and chased them out, killing a heifer. The wolves returned the next night to the same ranch but no cows were killed.

Russ Morgan, ODFE’s wolf coordinator, said the Imnaha pack has killed 19 cows since spring 2010. Usually wolves go after calves, which are the easiest prey, but the past three cows killed were adults or adult-sized, Morgan said.

“It’s worrying for livestock producers,” he said. “It’s an alarming trend.”

The agency would like to kill two wolves in the pack of at least five animals but a court-ordered stay halted that plan Oct. 5. Wildlife advocates, who took the agency to court, want the state to focus more preserving gray wolves which are protected in Oregon as an endangered species.

But:

Rob Klavins of Oregon Wild said that the number of livestock killed by gray wolves is miniscule compared with the numbers that die being born, in severe weather or from disease. Ranchers also lose cows to thieves.

The Imnaha pack is the first wolf pack in Oregon in more than 60 years. But instead of protecting and celebrating the return of the species, special interests in Oregon are working to eliminate wolves for fear of livestock depredation.

Imnaha Pack alpha male (ODFW)

The wolf pack was the first to establish and produce pups in the state in more than 60 years. While measures should be taken to prevent depredation of livestock, there are better ways to keep cattle safe than killing the family of Journey, who captured the nation's imagination with its thousand-mile expedition to become the first wolf in California in nearly a century.

Last fall, the Center for Biological Diversity and allies won an emergency stay of execution from the Oregon Court of Appeals that stopped the state from killing two wolves in the pack -- a stay that remains in place while the Cattlemen's Association pushes this appalling bill.