"Predators pursue disproportionately more of a plentiful prey species, and less of scarce prey, but change to the latter if it becomes relatively more abundant"......................... "Known as "prey switching," this phenomenon is ecologically important, because it helps to stabilize wildlife populations".................. "But what if the more abundant prey is more dangerous?"...................Utah State biologists Aimee Tallian and Dan MacNulty report that "Yellowstone Wolves seldom hunted adult bison(even as their populations have increased in the Park) because their hunting success(the wolves) was limited to a narrow set of conditions, including larger wolf packs chasing smaller bison herds with vulnerable calves"............ "Instead, wolves tend to scavenge bison carrion and did so more frequently as bison abundance increased."..............Makes total sense: Why get your head kicked in, gored and killed by 1000 pound adult Bison if you can make a living scavenging their winter killed carcasses as well as taking a % of their newborn fawns each Spring..................Ecologist George Wuerthner pointed out to me that as the Park Supervisors continue to kill and remove Bison that wander out of the Yellowstone in Winter, their are fewer dead Bison for Wolves to scavenge, upping the ante on Wolf survival during the Winter months

In harm's way: Wolves may not risk 'prey switching' ecologists say

 April 10, 2017 by Mary-Ann Muffoletto, Utah State University

https://phys.org/news/2017-04-wolves-prey-ecologists.html

In Yellowstone National Park, wolves cautiously stalk bison. Utah State University ecologists report wolves seldom hunt bison, though plentiful, because the latter is dangerous prey. Instead, wolves pursue elk, a scarcer yet safer target. Credit: Daniel Stahler, NPS

Ecologists have long observed predators pursue disproportionately more of a plentiful prey species, and less of scarce prey, but change to the latter if it becomes relatively more abundant. Known as "prey switching," this phenomenon is ecologically important, because it helps to stabilize wildlife populations. But what if the more abundant prey is more dangerous?

Utah State University researchers Aimee Tallian and Dan MacNulty report Yellowstone wolves seldom hunt bison, though plentiful, and, instead, pursue elk, a scarcer, yet safer target. Tallian and MacNulty, along with colleagues from the Yellowstone Center for Resources, the University of Montana and Oregon State University, discuss findings gleaned from long-term data collected from northern Yellowstone National Park in the April 11, 2017, issue of Functional Ecology.


A lone Wolf can kill a Wolf calf,,,,,,,,,,,,,,A large pack needed to kill an adult

A 2012 recipient of a National Science Foundation Graduate Research Fellowship, Tallian's research was performed under a NSF Graduate Research Opportunities Worldwide grant. MacNulty is supported by a grant from NSF's Long-Term Environmental Biology program.

"Prey switching has been observed in natural systems, where prey are small and generally helpless when attacked by a predator," says Tallian, who completed a doctoral degree at USU in 2017 and is lead author of the paper. "Imagine, for example, a lynx preying on snowshoe hares and squirrels."

But the playing field becomes decidedly unlevel for wolves in their pursuit of much larger bison. An adult male bull, after all, typically weighs nearly a ton.

"Our data reveal wolves maintained a strong preference against bison, even when bison were twice as abundant as elk," says MacNulty, assistant professor in USU's Department of Wildland Resources and the USU Ecology Center

Utah State University wildlife ecologist Aimee Tallian, pictured at a campsite in Yellowstone National Park's Pelican Valley, reports the ability of wolves and other predators to shift between hunting and scavenging is an under-appreciated 

"Hunting is hazardous business for wolves," says MacNulty, who's witnessed wolves kicked, gored and stomped to death by bison and other large prey. "Wolves minimize the risk of injury by focusing on more vulnerable prey, which are generally rare."

For this reason, he says, risk-averse wolves spend a lot of time on the move searching for the safest target. Any injury that slows them down may eventually kill them.

Tallian says the study further revealed wolves were increasingly resistant to hunting bison as relative bison abundance increased.

"Wolves seldom hunted bison because their hunting success was limited to a narrow set of conditions, including larger wolf packs chasing smaller bison herds with vulnerable calves," she says. "Instead, wolves tended to scavenge bison carrion and did so more frequently as bison abundance increased."

Tallian says wolf scavenging on bison carrion may divert predation away from elk, helping stabilize elk population dynamics.

"The ability of wolves and other predators to shift between hunting and scavenging is an under-appreciated behavior that may play an important role in the dynamics of ecological communities with dangerous prey," she says.

 Explore further: The more the merrier: Ecologists say larger group aids wolves' bison hunting

More information: Functional Ecology (2017). DOI: 10.1111/1365-2435.12866

Read more at: https://phys.org/news/2017-04-wolves-prey-ecologists.html#jC