Space to survive: Even wolves need room, new USU study finds
Dan Stahler, National Park Service
LOGAN — Having your own space not only brings peace of mind, but it also correlates strongly to a greater chance of survival for wolf families at Yellowstone National Park.
A new study involving Logan's Utah State University and University of Oxford found wolves will fight to the death to protect their turf if they lack adequate space to raise their pups.
The aggressive behavior of families looking out for their own is not limited to wolves, or the wilds of nature, said researcher Dan MacNulty, a USU ecologist and assistant professor in the Department of Wildland Resources.
"These family groups of wolves that are competing with each other for space and resources. That is not unlike humans," he said. "It is well-demonstrated that chimpanzees will compete and war with each other over space and resources and certainly humans are known to do so, if in a more sophisticated way."
The study, published in the online issue of the Journal of Animal Ecology in the British Ecological Society, followed 280 collared wolves in northern Yellowstone for 13 years.
"This study produced a generally novel result because the conventional thinking is that large carnivores are limited by the abundance of prey in a given area," MacNulty said. "But what these wolves are ultimately limited by is the amount of space they have to raise their pups in safety."
Wolves killing wolves is their No. 1 cause of death in Yellowstone and MacNulty said the research showed that adult survival rates dropped below 70 percent if there were greater than 65 wolves per 1,000 square kilometers.
These key observations in wolf infanticide may provide helpful lessons for management of wolf populations because of the insights they deliver, he said.
"For those concerned about wolf populations, even when you have super abundant prey like in Yellowstone, there are limits to wolf population growth. There is an intrinsic limit to the number of wolves that occupy a given space," MacNulty said, adding that because rival packs will attack and kill rival wolf pups, their numbers are self-limiting.
"What this paper does say is, though there is this notion that wolves will increase like a locust without any sort of natural limit, that idea is not supported by the data," he said.
MacNulty, who has been studying the wolves at Yellowstone for 19 years, said the rivalry among wolf families ramps up despite ample food when they are packed in too closely to one another.
"One of the things everyone needs to realize is that these wolf packs are not random collections of individuals," he said. "They are packs led by parents, with the offspring of the current year and preceeding years, often with aunts and uncles who are related to the breeding male and females. More wolves meant more fighting and killing. As a result, survival rates declined as wolf density increased.”
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