Tag: wolf

Scientists highlight global importance of meat-eating mammals

Coverage in the Sentinel about our carnivore paper in Science today.

Two UC Santa Cruz ecologists are among the authors of a global review of large carnivore populations published Jan. 10 in the journal Science. The international group of scientists warns that declines in these key species have broad, and often surprising, effects on ecosystems that extend to humans.

Read the full story here.

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Declining fortunes of Yellowstone’s migratory elk

This press release from Ecology nicely summarizes our recent Ecology paper in a forum discussing the fate of Yellowstone’s migratory elk.

“I think Middleton has an intriguing idea, and it might be what’s happening. We offer another hypothesis that also fits the data that they have. He says it’s climate change on the summer range and more predators on the summer range. I think it’s because there is irrigation that provides the sedentary elk with food. And I think it’s also that there is predator control outside the park,” said Wilmers.

While wolves and grizzlies have been thriving inside the park, predator control measures have intensified outside the park, Wilmers said. “My hypothesis is that in that crucial winter period, the migrants are coming down to range that the resident elk have already been feeding on all summer, and now they are competing for in the winter,” he said. To distinguish between these two stories would require hypothesis testing, he said – pitting them against each other and testing them with more data.

Read the entire press release here.

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Top Cats: How Pumas and Other Apex Predators’ Populations Affect The Big Biodiversity Picture

Here’s a great article by Liza Gross in KQED’s Quest.  It ties our recent puma work nicely together with other work on predator effects on ecosystem function.

These “top down” trophic cascades, which the ecologists dubbed “trophic downgrading,” have been documented from the poles to the equators and every major biome in between, making the loss of top predators, they wrote, “arguably humankind’s most pervasive influence on the natural world.” Earth has weathered five mass extinctions but never before at the hands of one species—human beings. And we humans seem hell bent on clearing the Earth of larger bodied apex predators.

I considered all this as I read a new paper from wildlife ecologist Chris Wilmer’s lab (published last week in PLOS ONE) that looks at how human development affects pumas. Like most large carnivores, pumas need vast territories to hunt, find mates and raise young. Pumas living in the San Francisco Bay Area have no such luck. Wilmers, an associate professor of environmental studies at the University of California-Santa Cruz, has been studying the effects of habitat fragmentation on the behavior, ecology and even the physiology of pumas around the Santa Cruz Mountains. He develops cutting-edge GPS collars to track both the location and behavior of his animals.

Fragmented landscapes often pave the way to extinction for wide-ranging large carnivores like pumas, with cascading effects. Freed from the threat of top predators, smaller carnivores like foxes increase in number, driving declines in birds and small mammals. But habitat fragmentation can produce effects similar to extinction because large predators tend to avoid small fragmented parcels. Given the heterogeneous patterns of human developments—with houses and other structures interspersed among natural areas—predicting how animals might respond, and with what consequences, presents a serious challenge.

Read the full article here.

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Fear and Loathing in Wolf Country

Here’s a great all around article about wolves by Liza Gross, just appearing in QUEST, which draws on some of our research in Yellowstone and Alaska.

Though Ecology 101 tells us that healthy ecosystems need top predators, researchers are just beginning to understand how the presence—and absence—of wolves affects other species.One study found that wolves may buffer the effects of climate change in Yellowstone National Park, where winters have been getting shorter, by leaving their moose and elk leftovers for eagles, ravens, coyotes and other scavengers. Another papersuggests that the absence of wolves may explain the precarious status of the Canada lynx. No wolves means more coyotes—which hunt snowshoe hares, the lynx’s favorite food—and more elk and deer—which eat the shrubby vegetation that sustain and shelter hares. And a 2011 paper in Biological Conservation supports earlier work showing that wolves in Yellowstone influence the behavior of deer and elk, releasing grazing pressure on vegetation, which in turn increases songbird habitat and diversity.

Read the full article here.

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Why the Beaver Should Thank the Wolf

From the NY Times, a great op-ed piece connecting our work on sea otters with wolves and elk in Yellowstone!  Couldn’t be more perfect.  Notice the little Sea Otter poking his head out of the reads below the elk.

Scientists call this sequence of impacts down the food chain a “trophic cascade.” The wolf is connected to the elk is connected to the aspen is connected to the beaver. Keeping these connections going ensures healthy, functioning ecosystems, which in turn support human life.

Another example is the effect of sea otters on kelp, which provides food and shelter for a host of species. Like the aspen for the elk, kelp is a favorite food of sea urchins. By hunting sea urchins, otters protect the vitality of the kelp and actually boost overall biodiversity. Without them, the ecosystem tends to collapse; the coastal reefs become barren, and soon not much lives there.

Read the full article here.

Here’s the full photo!

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Wolves Buffer Scavengers Against Climate Change

From Conservation Magazine, a story about our PLoS Biology article documenting the influence of wolves on scavengers as the climate changes.

Wolves and other top predators may help other species cope with climate change. Milder winters in Yellowstone National Park mean fewer elk (Cervus elaphus) die late in the season, which is tough on bald eagles (Haliaeetus leucocephalus), grizzly bears (Ursus arctos), and other scavengers that depend on the carcasses.

New research shows that wolves help scavengers by killing elk and thus providing more late-winter carrion. “Wolves act to retard the effects of a changing climate on scavenger species,” say Christopher Wilmers and Wayne Getz of the University of California, Berkeley, in PLoS Biology.

Many scavengers — from ravens (Corvus corax) and bald eagles to grizzly and black bears (Ursus americanus) — rely on carrion to get them through the winter in Yellowstone. However, without gray wolves (Canis lupus), carrion got scarcer as late winters got milder because deaths of elk depended primarily on snow depth. But after wolves were reintroduced in 1995, they once again became the primary cause of elk death and thus carrion availability.

To see whether wolves could buffer the impact of climate change on late-winter carrion, Wilmers and Getz analyzed 55 years of weather data from northern Yellowstone National Park, which has the park’s largest elk herd (at perhaps 10,000) and nearly 100 wolves. The researchers then estimated carrion availability with and without wolves by using models that accounted for factors including snow depth, wolf pack size, and elk kill rate as well as changes in the wolf and elk populations.

The weather analysis showed that Yellowstone’s winters have gotten shorter and milder, with shallower snow in the late winter months of March and April. The models confirmed that wolves do buffer the impact of milder winters on carrion availability: late-winter carrion drop-ped sharply as temperature increased without wolves but largely rebounded with them. Specifically, March elk deaths declined 27 percent without wolves vs. only four percent with wolves; April elk deaths declined 66 percent without wolves vs. only 11 percent with wolves.

“Late winter carrion in Yellowstone will decline with or without wolves, but by buffering this reduction, wolves extend the timescale over which scavenger species can adapt to the changes,” say Wilmers and Getz. They are now testing whether scavenger populations are in fact higher in areas where wolves have been reintroduced.

This work also shows that there is no substitute for intact ecosystems. “Their conclusions challenge the notion that human hunting serves as a surrogate to wild carnivore predation. Wolves distribute carrion widely in time and space, whereas modern human hunters do not,” says Douglas Smith of the National Park Service, who leads the Yellowstone Wolf Project.

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Wolves’ Leftovers Are Yellowstone’s Gain

From National Geographic, a nice article about our recent work on the effects of gray wolves on scavengers in Yellowstone NP.

Amid controversy, gray wolves (Canis lupus) were reintroduced to Yellowstone National Park in 1995. Now, new studies are hinting at the added benefits that the once-spurned carnivore have rapidly brought to the preserve.

Research published last month revealed that—unlike other top predators—Yellowstone’s wolves routinely leave unfinished elk (Cervas elephas) and moose (Alces alces) carcasses. These provide essential scraps for scavenging coyotes (Canis latrans), eagles, and other animals. Related work suggests that these carcasses provide dinner more consistently, and for more species, than remains discarded by human hunters.

Other recently published findings show that wolves may also be rebalancing Yellowstone’s ecosystems. Some streamside trees, such as species of cottonwood (Populus) and willow (Salix) are growing vigorously once more in areas overgrazed for much of the last century, researchers wrote.

“Part of the integrity of the ecosystem has been restored,” said Christopher Wilmers, an ecologist of the University of California, Berkeley, and lead author of two of the studies. The findings vindicate the decision to bring wolves back, he said.

Wiped Out

Wolves were systematically hunted in Yellowstone and much of the Western United States from the 1800s onwards. Yellowstone’s last pack was eliminated in 1926.

“In the early 1900s no one stopped to consider the ecological role of wolves,” commented Robert Beschta, a forestry scientist at Oregon State University in Corvallis. “Wolves were considered a predator with no value and seen as a huge constraint on allowing a productive ecosystem to flourish,” he said. Wolves, mountain lions (Puma concolor), and coyotes (Canis latrans) were all targeted as threats to livestock and game, he said.

When the National Park Service first considered reintroducing wolves in the late 1980s, critics warned that the predators might seriously impact elk, deer, and moose herds. Nevertheless, 31 wolves were re-introduced in 1995 and 1996 to Yellowstone, which spans portions of Idaho, Montana, and Wyoming. That population, now living in the vast park and its surroundings, had swelled to 220 animals in 21 packs by the end of 2001.

While elk numbers have been reduced by around 18 percent since the mid-1990s, few devastating impacts associated with the reintroduction program have yet been recorded, said Wilmers.

Feeding the Masses

Instead, the park is now enjoying some wolf-related benefits. According to Wilmers and colleagues’ study, published in the November Journal of Animal Ecology,wolves may be providing other scavengers with more regular meals than they’ve had since the early 20th century.

Mountain lions and grizzly bears (Ursus arctos) have a habit of sticking close by their kills, even when full. Wolves, on the other hand, tend to move away to “sleep off their meal,” said Wilmers, making meat available for scavengers.

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Alaska Bay Area British Columbia carbon climate change collars Colorado connectivity corridor coyote elk energetics evolution fish habitat fragmentation Lyme disease overexploitation predator puma salmon scavenger sea otter treadmill wolf Yellowstone

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