LOGAN -- A few hardworking individuals take on the most troublesome tasks while the rest of the group waits around to enjoy the benefits.
Yes, we could be talking about your family or your office co-workers.
But, no, we are talking about wolf packs attacking large prey in the wild.
Dan MacNulty, a Utah State University professor in the Department of Wildland Resources who has been involved with the Yellowstone Wolf Project since 1995, has observed which wolves risk their lives in the hunt and which hang back a safe distance until dinner is served.
"I liken it to a family dinner where individuals show up to eat, but they do little else," MacNulty said with a laugh.
"What we discovered is that hunting success increased with groups up to four wolves, then leveled off," he said. "With groups of more than four, we observed that individual hunting effort decreased."
The most aggressive hunters fall into two categories: breeders who have offspring to provide for, and young adults age 1 to 2, MacNulty said.
Typically, a wolf pack includes only one breeding pair and both males and females join the hunt.
So after the hunt has its four primary hunters, more may join the hunt but are less likely to risk their lives to take down a large elk or bison, or even a deer.
"If there's an opportunity for an individual to step up without risking injury, he will do so, without a doubt," MacNulty said. "Wolves are risk-averse. The problem for wolves from a hunting standpoint is to kill without being killed."
Because a wolf's median lifespan is only about five years, and the animals begin hunting so young, MacNulty believes much of the wolf's hunting "knowledge" is inborn and likely a result of natural selection.
Wolves also know how to pick their prey for minimal danger to themselves.
"You always hear about wolves hunting vulnerable prey, and it's true," MacNulty said.
"They kill primarily the young, the old or sick, or animals stuck in terrain traps, like deep snow."
Middle-aged, healthy prey is rarely targeted, except when it is trapped and unable to deliver a fatal blow to its pursuers, MacNulty said.
"I have seen bison kill wolves," he said.
MacNulty, a California native recently arrived from his former teaching post at the University of Minnesota, said hunting groups of three can always be improved by a fourth, but beyond that, the size of the group seems to make little difference in hunting effectiveness.
"In small groups, there's less temptation and opportunity to 'free-ride,' " he said.
MacNulty conducted the study with colleagues Douglas Smith, of the Yellowstone Center for Resources; David Mech, of the U.S. Geological Survey's Northern Prairie Wildlife Research Center; John Vucetich, of Michigan Technological University; and Craig Packer, of the University of Minnesota.
They used modern statistical techniques and direct observations of individually known wolves hunting elk in Yellowstone National Park.
MacNulty said the study's main benefit is to correct the misperception that large packs are more successful hunters.
"It rules out the roles of group hunting behavior as a factor driving the formation of large groups," he said. "There may be other reasons wolves form large groups, but it has nothing to do with their hunting success."
The study findings appear in the September-October 2011 issue of Behavioral Ecology.
Comments