Monday, February 13, 2017

Snow leopard and Himalayan wolf diets are about one-quarter livestock


Around a quarter of Himalayan snow leopard and wolf diets are livestock, the rest being wild prey, according to a study published February 8, 2017 in the open-access journal PLOS ONE by Madhu Chetri from Inland Norway University of Applied Sciences, Norway, and colleagues.

Killing livestock creates conflicts between top predators and pastoral communities, and is a main challenge for conserving snow leopards, which are endangered, and Himalayan wolves, which are rare. These wolves prefer the open grasslands and alpine meadows that are also frequented by pastoral herders, and snow leopards prefer the steep terrain associated with montane pastures. To assess prey preferences of these carnivores, Chetri and colleagues analyzed DNA and hairs in 182 snow leopard scats and 57 wolf scats collected in the Central Himalayas, Nepal.

The researchers found that in keeping with the predators' habitats, snow leopards preferred cliff-dwelling wild prey such as bharal, while wolves preferred plain-dwelling wild prey such as Tibetan gazelles. In addition, livestock comprised 27% of the snow leopard diet and 24% of the wolf diet. Livestock occurred more than twice as frequently in scats from male snow leopards than in scats from females. Although livestock constitutes a substantial proportion of the predator's diets, little is known about the actual predation impact on the pastoral communities. Hence, the researchers' forthcoming work focuses on estimating livestock mortality rates and identifying factors associated with livestock loss.

Wednesday, February 8, 2017

Brown bears reduce wolf kill rates says USU ecologist


Contrary to popular assumptions, researchers on two continents find wolves kill less often in the presence of brown bears
UTAH STATE UNIVERSITY
IMAGE
IMAGE: IN NORTH AMERICA'S YELLOWSTONE NATIONAL PARK, HUNGRY WOLVES WAIT TO ACCESS THEIR ELK KILL AS BROWN BEARS FEAST ON THE SPOILS. UTAH STATE UNIVERSITY ECOLOGIST AIMEE TALLIAN AND COLLEAGUES REPORT... view more 
CREDIT: DANIEL STAHLER, NATIONAL PARK SERVICE
LOGAN, UTAH USA - If you've ever been elbowed out of the way at the dinner table by older, stronger siblings, you'll identify with wolves competing with larger bears for food. A study by Utah State University ecologist Aimee Tallian and colleagues reveals wolves might be at more of a disadvantage than previously thought.
Tallian is lead author of a paper examining competition between wolves and brown bears on two continents published Feb. 8, 2017, in Proceedings of the Royal Society B[DOI: 10.1098/rspb.2016.2368]. 
"Wolves and brown bears coexist across most of their range," says Tallian, who completed a doctoral degree from USU in 2017. "Although competition between predators such as these is widespread in nature, we know little about how brown bears affect wolf predation."
With colleagues in Scandinavia and North America, Tallian examined how brown bears affected wolf kill rates at study sites in northern Europe and Yellowstone National Park.
"We found an unexpected pattern," she says. "Wolves killed less often in the presence of brown bears, which is contrary to the common assumption that wolves kill prey more often to compensate for loss of food to bears."
Tallian says the consistency in results between the systems on different continents suggests brown bear presence actually reduces wolf kill rate, but the researchers aren't sure why.
They surmise wolves, unlike lynx and mountain lion, may not be quickly abandoning their kills, as bears move in take advantage of the spoils.
"The wolves may be hanging around longer, waiting their turn to gain access to food," Tallian says.
She and her colleagues also wonder if wolves kill less frequently because it takes them longer to find prey.
"We think this may be the case, in the spring, when newborn ungulates make easy pickings for bears," Tallian says. "It may simply take more time for wolves to find calves, when there are fewer of them."
Interactions between apex predators can either relax or strengthen their effect on prey and predator populations, she says.
"The team's results suggest that ignoring such interactions may underestimate the effect competition between predators can have on predator populations," Tallian says. "In addition, it's possible to overestimate the impact of multiple predators on prey populations."