Friday, March 29, 2013

Black Bears: Here, Gone, and Back Again

A new study from the Wildlife Conservation Society (WCS) and the Nevada Department of Wildlife ( NDOW) has pieced together the last 150 years of history for one of the state’s most interesting denizens: the black bear.

The study, which looked at everything from historic newspaper articles to more recent scientific studies, indicates that black bears in Nevada were once distributed throughout the state but subsequently vanished in the early 1900s. Today, the bear population is increasing and rapidly reoccupying its former range due in part to the conservation and management efforts of NDOW and WCS.__Compelled in part by dramatic increases in human/bear conflicts and a 17-fold increase in bear mortalities due to collisions with vehicles reported between the early 1990s and mid- 2000s, WCS and NDOW began a 15-year study of black bears in Nevada that included a review of the animal’s little-known history in the state.

Over the course of the study, black bears were captured both in the wild and at the urban interface in response to conflict complaints. The captured animals used in the study (adult males and females only) were evaluated for multiple physiological indicators including condition, sex, reproductive status, weight, and age, prior to being released. From the information gathered, the population size in the study area was estimated to be 262 bears (171 males, 91 females).

Confirmed sightings and points of capture from 1988 to present were mapped and presented in the report to illustrate current population demographics, and will be used to inform bear management in Nevada.

“It’s critical to understand the population dynamics in a given area in order to make informed decisions regarding management,” said WCS Conservation Scientist Jon Beckmann. “This includes decisions on everything from setting harvest limits to habitat management to conservation planning in areas where people will accept occupation by bears. We used this long-term study to determine if reported incidences were due to an increasing or expanding bear population, or people moving to where bears are located. The answer is both.”

The study area extended from the Carson Range of the Sierra Nevada eastward to the Virginia Range and Pine Nut Mountains, and from Reno south to Topaz Lake—an area collectively referred to as the Carson front. Because many captures were in response to conflicts, the urban interfaces of cities and towns of the Lake Tahoe Basin were included.

Nevada’s Black Bear History Unraveled

In looking to integrate information on the historical demographics of black bears into their study, the authors found that little published scientific research or data was available and that the species’ history in Nevada went largely ignored until 1987— when complaints arising from sightings and road collisions with vehicles began.

Historical records compiled by retired NDOW biologist Robert McQuivey that included old newspaper articles, pioneer journals dating as far back as 1849, and NDOW records that had long been unavailable, were reviewed and confirmed that black bears were present throughout the state until about 1931. At that point, the authors concluded that “the paucity of historical references after 1931 suggest extirpation of black bears from Nevada’s interior mountain ranges by this time.”

“The historical records paint a very different picture of Nevada’s black bear than what we see today. This new perspective is a good indication of what bear management in this state could involve should the population continue to expand,” said the study’s lead-author Carl Lackey of NDOW.

The authors believe that while over-hunting and conflicts with domestic livestock contributed to the bear’s local extinction in the Great Basin, landscape changes due to clear-cutting of forests throughout western and central Nevada during the mining booms of the late 1800s played an important role as well. But as fossil fuels replaced timber as a heat and energy source, forestry and grazing practices evolved, and reforestation and habitat regeneration occurred in parts of the their former range, the bears rebounded.__Using the information gathered in their review of historic documents, the scientists mapped the distribution of black bears within the interior of Nevada during the 1800s and early 1900s. They recommend that historical range maps for the species in North America be revised to include the information produced as part of the study.__The study, Bear Historical Ranges: Expansion of an Extirpated Bear Population, appears in the current online edition of the Journal of Wildlife Management. Co-authors include Carl W. Lackey of the Nevada Department of Wildlife, Jon P. Beckmann of the Wildlife Conservation Society, and James Sedinger of the University of Nevada, Reno.

Saturday, March 16, 2013

Carnivores, livestock and people manage to share same space study finds

In the southern Rift Valley of Kenya, the Maasai people, their livestock and a range of carnivores, including striped hyenas, spotted hyenas, lions and bat-eared foxes, are coexisting fairly happily according to a team of coupled human and natural systems researchers.

“I wouldn’t call the results surprising,” said Meredith Evans Wagner, a visiting scholar from the University of Florida in the Center for Systems Integration and Sustainability (CSIS) at Michigan State University and part of the research team. “Other research has shown that people and carnivores can coexist, but there is a large body of thought that believes carnivores need their own protected space to survive.”

The paper “Occupancy patterns and niche partitioning within a diverse carnivore community exposed to anthropogenic pressures” was recently published in Biological Conservation. Other authors are Paul Schuette and Scott Creel, of Montana State University, and Aaron Wagner, postdoctoral researcher in the BEACON Center for the Study of Evolution in Action at Michigan State.

The paper’s findings echo results of a study published in PNAS in September 2012 by Jianguo “Jack” Liu and Neil Carter of CSIS: namely that tigers and people are sharing the same space in Chitwan National Park in Nepal, albeit at different times.

Wagner and her colleagues spent just over two years documenting the carnivores of the southern Rift Valley, using motion-detecting camera traps to captures images of the creatures and people using four different areas of land: a conservation area with no human settlements, a grazing area that also had no human settlements, a permanent settlement area, and a buffer zone between the grazing and conservation areas that included seasonal human settlements.

While most of the results were expected – the majority of carnivore photos were taken after dark, most of the larger predators, such as lions and spotted hyenas, tended to be found in the conservation area that didn’t include any human settlements – there were some intriguing results.

“We found that while there were more striped hyenas in the conservation area, there were also striped hyenas in the buffer zone, close to the human settlement area,” Wagner explained. “The hyenas weren’t avoiding that area; they were using the settlement area as a resource in addition to hunting.”

When the Maasai slaughtered an animal for food, they throw the scraps out their back doors, which are at the edge of the buffer zone, where the striped hyenas were happy to eat them.

“Carnivores aren’t a problem for this group of Maasai,” Wagner said. “They’ve made a conscious decision to not hunt carnivores. If one of their livestock is killed by a carnivore, people don’t go out and kill a carnivore in retaliation. It’s a little bit unusual in that way. But in our study, we found that carnivores killing livestock didn’t happen a lot.”

“Wildlife is clearly driven away from the permanent settlement areas," said Aaron Wagner. "But the seasonal human migration out of the buffer zone keeps that area viable for wildlife. Numbers drop when the cattle and people move in, but the striped hyenas seem to have habits that allow them to compensate. They do scavenge around bomas [Maasai settlements] when the pickings are good, but they hunt, too. Even with the people around, there are enough prey left, or enough trickling in from the conservation area, that they have plenty to hunt. More often than not, when following a striped hyena that’s foraging (or playing at a den) at 3 a.m., there’s no indication that people are so close.”