Black bears in Yosemite forage primarily on plants and nuts

Black bears in Yosemite National Park that don't seek out human foods subsist primarily on plants and nuts, according to a study conducted by biologists at UC San Diego who also found that ants and other sources of animal protein, such as mule deer, make up only a small fraction of the bears' annual diet.

Their study, published in this week's early online edition of the journal Methods in Ecology and Evolution, might surprise bear ecologists and conservationists who had long assumed that black bears in the Sierra Nevada rely on lots of protein from ants and other insects because their remains are frequently found in bear feces. Instead, the researchers believe that bears likely eat ants for nutrient balance.

Rather than relying on indigestible foods found in bear feces for information about the importance of digestible bear foods, the UC San Diego ecologists looked at the digestible foods that were used to produce bear tissue. They accomplished this by measuring the abundances of carbon and nitrogen isotopes found in different species of plants and animals, and used a statistical approach to relate them to the carbon and nitrogen isotopes measured in bear hair. This allowed the scientists to quantify what the bears ate, then assimilated into their hair. 

The scientists also applied the same technique to Norway rats in Alaska's Aleutian Islands and determined that this invasive species subsisted largely on terrestrial plants and seasonal pulses of marine amphipods, rather than marine birds as had been long assumed. 

"Rats tend to dominate the habitats they invade on islands, killing much of the native fauna, especially birds, which is a serious conservation issue," said Carolyn Kurle, an assistant professor of biology at UC San Diego who conducted the study with Jack Hopkins, a postdoctoral fellow. "Using stable isotopes, we confirmed that marine birds have been extirpated to such levels on the islands where we worked that rats don't eat them anymore." 

"Both rats and black bears are omnivores with complex diets consisting of both plants and animals," said Hopkins. "To our knowledge, no study before this has accurately estimated the relative importance of plants and animals to the diets of these omnivore populations."

Hopkins said he and Kurle found in their study that plants and acorns are black bears' primary food sources in Yosemite. "We also learned that female bears foraged for high-fat acorns and pine nuts more heavily than males, suggesting that females likely need these seeds for reproduction. This could be a real problem for Sierra black bears in the future if blister rust continues to kill sugar pines and sudden oak death moves in from the coast."

Besides resolving the issue of what black bears and Norway rats actually use for growth and function, the scientists said a major goal of their study was to demonstrate how the use of stable isotopes derived from animal tissues and their prey could be used to quantify the resource use of other omnivores with complex diets.

"Ecologists currently focus too much attention on measuring the variation of isotope data for consumers and their prey and not enough attention on quantifying the interactions of consumers and their prey using isotope data," Hopkins explained. "Measuring such interactions and their relative strengths can help us understand the impacts animals have on their environment." 

Over the past two decades, black bears in Yosemite were involved in more than 12,000 reported incidents within the national park, injuring nearly 50 people and causing $3.7 million worth of property damage. In response to these problems, Congress has appropriated over $8 million since 1999 to mitigate human-bear conflicts in Yosemite.

Those efforts appear to be working. In a study published last year in the journal Frontiers in Ecology and the Environment, Hopkins and other scientists measured the stable isotopes of carbon and nitrogen in the hair and bone of Yosemite bears over the past century and found that since 1999, the proportion of human-derived food in bear diets has dramatically declined.

"Yosemite bears currently consume human foods in a similar proportion as they did in the early 1900s," said Hopkins. "This suggests a notable management achievement in the park, considering that thousands of people visited Yosemite annually in the early 1900s, while about four million people visit each year today."

Recovering predators create new wildlife management challenges

The protection and resurgence of major predators such as seals, sea lions and wolves has created new challenges for wildlife managers, including rising conflicts with people, other predators and, in some cases, risks to imperiled species such as endangered salmon and steelhead, a new research paper finds.

The study by scientists from NOAA Fisheries' Northwest Fisheries Science Center and the University of Washington examines recovering predator populations along the West Coast of the United States and in the Greater Yellowstone ecosystem, and the conflicts surrounding them. The study was published today in the journal Conservation Letters.

In the Pacific Northwest, for example, California sea lions that have increased under the Marine Mammal Protection Act have increasingly preyed on endangered salmon. Wolves reintroduced to Yellowstone in 1995 have since cut into elk herds, reducing human hunting opportunities.

"Increases in predators can be seen as successful in terms of efforts to recover depleted species, but may come at a cost to other recovery efforts or harvest of the predators' prey," said Eric Ward, a NOAA Fisheries biologist and coauthor of the paper.

The scientists describe three types of conflicts that can emerge as predators rebound under the protection of the Endangered Species Act and Marine Mammal Protection Act:

• Increased competition with humans for the same prey. For instance, sea lions eating fish also pursued by anglers and wolves preying on livestock and reducing elk numbers.
• Predators consuming protected or at-risk prey species, such as sea lions eating salmon and grizzlies consuming Yellowstone cutthroat trout.
• Protected predators competing with each other for prey. For example, sea lions consuming the same fish as killer whales, with wolves and grizzly bears also preying on the same species.

Pacific Northwest waters include many such conflicts, largely because many top predators such as sea lions, elephant seals and several whales are increasing in number and prey upon salmon, steelhead, rockfish and other fish protected by the Endangered Species Act.

Conservation conflicts have also emerged elsewhere: On California's San Clemente Island, a threatened island fox species preys on an endangered shrike, while protected golden eagles prey on both the fox and the shrike. Also in the Pacific Northwest, protected barred owls are moving into forest habitat long important to threatened spotted owls and double-crested cormorants, like sea lions, have been targeted for culling to reduce predation on Columbia River salmon.

The scientists call for improved monitoring and modeling to better anticipate interactions between predators and prey, and assess whether steps to manage predators may be warranted. Where conflicts continue, the scientists suggest developing multi-species recovery plans that consider the tradeoffs between increasing predators and other protected species.

"Predators such as bears, wolves and whales are charismatic creatures often seen as bellwethers of ecosystem health," said Kristin Marshall, a postdoctoral researcher at NOAA Fisheries who completed graduate research in Yellowstone and lead author of the paper. "We're fortunate to have places such as Yellowstone and the Northeast Pacific where they can recover, but in protecting one species you have to be thinking ahead to account for cascading effects that may impact other species too."

The ESA and MMPA do recognize larger ecosystem needs. For instance, the first purpose of the ESA is "to provide a means whereby the ecosystems upon which endangered species and threatened species depend may be conserved," and the MMPA seeks to "maintain the health and stability of the marine ecosystem." Both NOAA Fisheries and public land managers in the Yellowstone region are increasingly pursuing ecosystem-based management with those goals in mind. Research has also found ecological benefits from the reintroduction of wolves in Yellowstone.

Both the ESA and MMPA also provide safety valves by allowing limited control of recovering predators to manage their impacts under certain circumstances.

NOAA Fisheries has authorized states under the MMPA to remove sea lions known to be preying on endangered salmon, for instance. An "experimental" designation under the ESA allowed for removal of wolves that attacked livestock, although wolves are no longer listed as endangered in Montana and Idaho and are now subject to hunting.

But the scientists note that resolving conflicts by culling predators may itself have unintended consequences and will face public and legal opposition that may limit management options.

"Thirty years ago scientists predicted that increases in predator populations would cause more of these conflicts to emerge," Ward said. "We've largely seen these predictions come true, and there's no indication of these conflicts decreasing."

Down to 3 wolves on Isle Royale

CREDIT: ROLF PETERSON

Only three wolves seem to remain in Isle Royale National Park. Researchers from Michigan Technological University observed the wolves during their annual Winter Study, and the lone group, at an unprecedented low, is a sharp decline from nine wolves observed last winter.

The study's report, released today, marks the project's 57th year of observing wolves and moose in Isle Royale. It is the longest running predator-prey study in the world. This year, along with the three resident wolves, scientists estimated 1,250 moose on the island and observed two visiting wolves, which came and then left across an ice bridge to the mainland. This growing gap between the predator and prey populations is a trend that Michigan Tech researchers have tracked over the past four years.

"It's not the presence of wolves that matters so much, it's whether wolves are performing their ecological function," says John Vucetich, an associate professor of wildlife ecology who leads the study along with Rolf Peterson, a research professor at Michigan Tech.

Last April, the Isle Royale National Park released a statement concerning wolf intervention options. Part of the statement reads: "There is still a chance of nature replenishing the gene pool as wolves are able to move to and from the island when ice bridges form."

But with only three wolves remaining, Vucetich says, "There is now a good chance that it is too late to conduct genetic rescue." He also points out that one of the Isle Royale wolves left on an ice bridge last winter, and this winter, two wolves visited the island and promptly traveled back over the ice bridge.

Wolf Genetics

To understand Isle Royale wolves, you have to understand their genetics. Inbreeding has greatly impacted the packs over the past half century, which is clear with the three remaining wolves.

The group is most likely made up of two adults and one nine-month-old pup, possibly the adult pair's offspring. But unlike its pack mates, the pup does not appear healthy. It has a constricted waistline, hunched posture and seems to have a deformed tail, the researchers said.

"Those observations suggest that the pup is not well off," Vucetich says, noting that on the last day of the study, Peterson had found the two adult wolves, but not the pup. "It would not be surprising if the pup was dead a year from today."

Even if the pup were healthy, it would not necessarily be a promising sign. In the case of wolves, three is not a crowd. Such low numbers make the population's natural recovery unlikely. The wolves' numbers started plummeting in 2009, declining by 88 percent from 24 to 3 wolves, which Vucetich and Peterson think is a result of inbreeding. All geneticists who have studied the current situation agree that recovery is unlikely without new genetic material.

With that in mind, even if the surviving adults are a mating pair, their offspring probably would not fair well. While the researchers are waiting on genetic tests to confirm the wolves' identities and which pack they came from, their best guess is that they are the alpha pair from West Pack. And, as a mating pair, neither is likely to be interested in other potential mates introduced for genetic rescue.

Visiting Wolves

Looking for wolves in winter is challenging, Vucetich says, describing how he spends hours looking out a small plane window, searching for tracks or subtle signs. One day this winter, the work paid off in an unexpected way.

"I could see these two wolves, they were on top of a ridge, curled up in tight little balls," Vucetich says, explaining that the wolves were asleep. "And wolves can sleep for quite some time, so we circled for a bit and decided to come back later."

Of course, when Vucetich and the pilot came back, the wolves had trotted off. But based on the tracks and the geography of Isle Royale, Vucetich says it was easy to guess the wolves' preferred travel route. They found the canines skirting the shoreline soon after.

One wolf appeared light-colored, which is uncharacteristic of Isle Royale wolves, and the other was radio collared. They were visitors who had crossed an ice bridge from the US-Canadian mainland, where the Grand Portage Band of Lake Superior Chippewa had collared the wolf.

But they didn't stay long. Within the week, the wolves left, traveling back across the ice bridge.

"Everyone wants to know: What does this mean?" Vucetich asks. The answer is unclear, despite the fact that visiting wolves raise hopes for saving the population. Vucetich and Peterson write in their report that even "if the visiting wolves had been aware of the presence of Isle Royale wolves, it is far from certain that genetic rescue would have occurred."

The remaining two options, then, are to reintroduce wolves to the island or do nothing and see what happens naturally.

"One must use the word, 'naturally', carefully these days," Peterson advises. "The human imprint is written all over the dynamics of this wolf population in recent decades".

A case in point, he says, is the downward trend in the frequency of ice bridges in winter, which formerly allowed wolves with new genetic material to make their own way to Isle Royale.

Booming Moose Population

Along with wolves, the other iconic animals of Isle Royale are moose. And unlike their canine predators, and in spite of several harsh winters, the moose population has been growing annually at 22 percent for each of the past four years.

"If that was money in the bank, you'd get rich in a hurry," Vucetich says. "Soon we'll be moose rich."

While iconic, a proliferation of moose could actually be harmful and, if this trend continues, the population could reach past heights like in 1996.

"At that time the moose population had considerable impact on forest vegetation," Vucetich and Peterson write in the Winter Study annual report. "Concerns remain that the upcoming increase in moose abundance will result in long-term damage to the health of Isle Royale's vegetative community."

The balance of predator-prey on Isle Royale has clearly tipped. The question remains what actions humans will or will not take to influence that scale.

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The annual report is available at: www.isleroyalewolf.org

Lethal control of wolves backfires on livestock

WSU researchers find shooting carnivore leads to more dead sheep and cattle

Washington State University researchers have found that it is counter-productive to kill wolves to keep them from preying on livestock. Shooting and trapping lead to more dead sheep and cattle the following year, not fewer.

Writing in the journal PLOS ONE, WSU wildlife biologist Rob Wielgus and data analyst Kaylie Peebles say that, for each wolf killed, the odds of more livestock depredations increase significantly.

The trend continues until 25 percent of the wolves in an area are killed. Ranchers and wildlife managers then see a "standing wave of livestock depredations," said Wielgus.

Moreover, he and Peebles write, that rate of wolf mortality "is unsustainable and cannot be carried out indefinitely if federal relisting of wolves is to be avoided."

The gray wolf was federally listed as endangered in 1974. During much of its recovery in the northern Rocky Mountains, government predator control efforts have been used to keep wolves from attacking sheep and livestock. With wolves delisted in 2012, sport hunting has also been used. But until now, the effectiveness of lethal control has been what Wielgus and Peebles call a "widely accepted, but untested, hypothesis."

Their study is the largest of its kind, analyzing 25 years of lethal control data from U.S. Fish and Wildlife Services Interagency Annual Wolf Reports in Montana, Wyoming and Idaho. They found that killing one wolf increases the odds of depredations 4 percent for sheep and 5 to 6 percent for cattle the following year. If 20 wolves are killed, livestock deaths double.

Work reported in PLOS ONE last year by Peebles, Wielgus and other WSU colleagues found that lethal controls of cougars also backfire, disrupting their populations so much that younger, less disciplined cougars attack more livestock.

Still, Wielgus did not expect to see the same result with wolves.

"I had no idea what the results were going to be, positive or negative," he said. "I said, 'Let's take a look at it and see what happened.' I was surprised that there was a big effect."

Wielgus said the wolf killings likely disrupt the social cohesion of the pack. While an intact breeding pair will keep young offspring from mating, disruption can set sexually mature wolves free to breed, leading to an increase in breeding pairs. As they have pups, they become bound to one place and can't hunt deer and elk as freely. Occasionally, they turn to livestock.

Under Washington state's wolf management plan, wolves will be a protected species until there are 15 breeding pairs for three years. Depredations and lethal controls, legal and otherwise, are one of the biggest hurdles to that happening.

Wolves from the Huckleberry Pack killed more than 30 sheep in Stevens County, Wash., this summer, prompting state wildlife officials to authorize killing up to four wolves. An aerial gunner ended up killing the pack's alpha female. A second alpha female, from the Teanaway pack near Ellensburg, Wash., was illegally shot and killed in October.

That left three breeding pairs in the state.

As it is, said Wielgus, a small percentage of livestock deaths are from wolves. According to the management plan, they account for between .1 percent and .6 percent of all livestock deaths--a minor threat compared to other predators, disease, accidents and the dangers of calving.

In an ongoing study of non-lethal wolf control, Wielgus's Large Carnivore Lab this summer monitored 300 radio-tagged sheep and cattle in Eastern Washington wolf country. None were killed by wolves.

Still, there will be some depredations, he said. He encourages more non-lethal interventions like guard dogs, "range riders" on horseback, flags, spotlights and "risk maps" that discourage grazing animals in hard-to-protect, wolf-rich areas.

"The only way you're going to completely eliminate livestock depredations is to get rid of all the wolves," Wielgus said, "and society has told us that that's not going to happen."

Must See Video On Wolves and Ecology In Yellowstone

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Scientists Call for Increased Conservation Efforts to Save Black Bears

Between 1880 and 1920, the Central Interior Highlands (CIH), consisting of Missouri, Oklahoma and Arkansas, saw the height of deforestation that also decreased the habitat for black bears and other forest species. To combat the decline of black bears and repopulate the mountainous region, more than 250 bears from Minnesota and Manitoba were relocated to Arkansas in the 1950s and 1960s. Now, researchers at the University of Missouri have analyzed genetic diversity in black bears in the CIH and have determined that coordinated conservation management is still needed to maintain healthy populations of black bears in the region.

“The focus of our study was to determine the effects of the reintroduction of black bears in the Ozark and Ouachita Mountains and how that reintroduction affected population genetics in the region,” said Emily Puckett, a doctoral candidate in the Division of Biological Sciences at MU. “We also wanted to determine if we could find evidence of the population that was formerly here and whether or not they mated with the reintroduced bears or if they had gone locally extinct following deforestation.”

Study results suggested that black bears were present throughout the CIH in the 1920s, contrary to previous beliefs. Current research indicates that the bears had a remnant lineage in the northern Ozarks of Missouri, Puckett said.

Additionally, the team found that current black bears went through a brief “bottleneck,” where bears were cut off from each other and genetic diversity was reduced. However, the team also determined that the reintroduction of bears to the CIH in the 1950s and 1960s helped to restore diversity and increase population size in the Ozarks and Ouachitas.

“We observed the genetic signature of the Ozark population from Arkansas in Missouri, meaning that the bears moved north,” said Puckett. “These bears bring with them their higher genetic diversity which may help Missouri’s bear population in the future. The movement north also indicates that formerly fragmented forests may have regrown thereby connecting Missouri bears to the Ozark subpopulation that was further south.”

Puckett and her team including Lori Eggert, associate professor of biological sciences in MU’s College of Arts and Science, and Jeff Beringer from the Missouri Department of Conservation, collected and analyzed DNA samples from black bears from five geographical locations.  Hair samples from Arkansas, Oklahoma and Missouri were analyzed. Additionally, blood samples from hibernating bears in Minnesota and tissue samples from Manitoba were examined for their genetic signatures.

“This represented one of the largest sample sizes in a study of this type,” Eggert said. “By using multiple genetic markers on samples collected from Missouri and Arkansas, hunted bears in Oklahoma and live dens in Manitoba, we were able to conduct genetic and statistical analyses to analyze trends and gain robust conclusions.”

The team suggests that conservation efforts to promote forest connectivity will help protect bears throughout the region, so that subpopulations are not isolated, as was the case in Missouri, and genetic diversity remains high. State agencies in Arkansas, Oklahoma and Missouri could work together to unify bear management since this study observed populations spanning state borders.

“Geneticists get concerned when populations have low genetic diversity,” Puckett said. “Low diversity can be indicative of low population size. When harmful mutations arise in a gene pool with low diversity, they may increase in frequency leading to poor fitness and health in the population. That’s why these management suggestions are so important.”

The study, “Influence of drift and admixture on population structure of American black bears (Ursus americanus) in the Central Interior Highlands, USA, 50 years after translocation,” was published in the journal Molecular Ecology. Funding for the project was provided by the Missouri Department of Conservation, Arkansas Game and Fish Commission, U.S. Fish and Wildlife Service, and Safari Club International.

Grizzly bear 'highway' in coastal British Columbia

A novel, First Nations-led research collaboration has revealed a previously undocumented grizzly bear aggregation in coastal British Columbia, one of the most southerly aggregations of salmon-feeding grizzlies in North America. Using non-invasive DNA analysis, the authors describe a grizzly bear "highway," identifying nearly 60 individual bears, many who travelled hundreds of miles from surrounding areas to feed on autumn-spawning salmon in the Koeye River. The research was guided by the customary law and cultural practices of the Heiltsuk First Nation and recently published in the journal Ecology and Society.

Conducted over three years, the study also provides potential early evidence of a declining bear population in the area and links this to the decreasing availability of salmon. The project demonstrates a model for resource management by indigenous people, in which research is embedded within a socially and culturally appropriate framework.

"What's really novel here is the set of relationships, and deep cultural histories, that guided applied conservation science," said Chris Filardi, director of Pacific programs at the American Museum of Natural History's Center for Biodiversity and Conservation and an author on the paper. "In this collaborative setting, results are directly relevant to tribal leadership impacting conservation in ways that elude most scientific studies."

The study was centered in the Koeye River Conservancy, one of numerous protected areas designated by the Heiltsuk First Nation in the Great Bear Rainforest of British Columbia in 2009. The Heiltsuk people settled in this area more than 9,000 years ago and are now reasserting their rights as guardians of the Koeye River. To realize this renewal,

they established the Qqs (Eyes) Projects Society, a Heiltsuk-driven nonprofit that builds capacity for research, monitoring, and tribal governance of high-value stewardship areas. In 2006, the Heiltsuk people partnered with the Museum and The Nature Conservancy to implement a grizzly bear survey project with a unique dimension: from the outset, the study was designed to uphold the Heiltsuk Nation's Gvi'ilas, or customary law, a set of guiding principles that frame a worldview focused on core values.

"What appealed to us was the opportunity to root science in strong cultural stewardship frameworks," said Qqs' William Housty. "We articulate specific Heiltsuk laws and customs related to respect and reciprocity and match them with scientific tools and knowledge to put those principles in action."

During the survey, grizzly bear hair was collected as the animals walked by scented wire snares set up in the area during salmon-spawning season. As part of the non-invasive aspect of the work, the "baits" did not provide rewards to the bears visiting the snares.

At the same time, the team calculated the accessibility of salmon to bears with an index based on the number of salmon that return to the Koeye each year; water flow; and water visibility. Over the three-year survey, they found a decreasing population of bears in the Koeye, likely tied to declining salmon accessibility.

"This study shows that protected areas are not enough. We knew that bears are wide-ranging, but this study shows how vulnerable they are to a variety of threats," said Richard Jeo, a staff scientist for The Nature Conservancy. "Scientific insight can help guide management but the fate of these bears and the rainforest where they live is still largely in the hands of a few First Nations."

"We want to practice land and resource management with strong information empowering our decision makers," Housty said. "Whether it's regulating activities like forestry and tourism or indigenous-led advocacy to end trophy hunting for bears, ensuring that we ourselves are leading the best available science is a critical part of asserting our sovereignty and stewardship responsibility."

The next step for the group is to expand survey work to include a broader sampling of culturally significant salmon streams, improve linkages to salmon monitoring, and directly involve Heiltsuk families and their histories with places they share with bears.

"What is most important is Heiltsuk-driven science across the range of areas used by bears and people," Filardi said. "Knowledge about the interwoven ecologies of bears, salmon, and people can guide actions unavailable in places farther south where bears and salmon have vanished, or across broader society, where we have not yet come to value bears and salmon as integral to our physical and spiritual lives."