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Wildlife » Utah State scientist studied 13 years of data on the Yellowstone National Park wolf population.
By Lindsay Whitehurst | The Salt Lake Tribune
Wolves kill one another and the pups of competing packs in battles over territory even if there is plenty to eat, according to a new study from Yellowstone National Park.
The research is a rare glimpse into the way wolves behave when humans are generally out of the picture, said Utah State University ecologist Dan MacNulty.
“At the end of the day, the success of a wolf from an evolutionary perspective is based on how many pups it leaves behind,” said MacNulty, who worked with scientists from the University of Oxford and the Yellowstone Wolf Project on a new paper published online in the Journal of Animal Ecology. “If they’re packed close together, they have the opportunity to raid each other and kill pups and eliminate the competition.”
For a wolf, closeness is relative — as in 65 wolves per 1,000 square miles, the point at which adult survival rates drop below 70 percent.
The study, which will also appear in a print edition of the British Ecological Society publication, is based on 13 years of data from radio-collared wolves at Yellowstone. Until now, it’s been hard to say how a large population of the animals interact with one another in the wild because their numbers were tightly controlled.
The animals were eliminated from Yellowstone by the National Park Service in the 1920s. They were reintroduced starting in 1995 and grew to something unique in the country — a group of wolves protected from human development and hunting.
The population peaked in 2004, though, and has declined since — but not for lack of food. The canines had plenty of their main prey: elk, as well as bison, bighorn sheep and mule deer.
Rather, the No. 1 cause of death during the study period was other wolves.
“They need more than simply food,” MacNulty said. “That’s sort of an unappreciated aspect of their biology.”
If wolves leave the park looking for more elbow room, they can be hunted, hit by cars or otherwise affected by people, though they occasionally survive to establish new packs with Wyoming wolves.
Researchers, though, generally don’t follow the predators after they leave Yellowstone.
The research suggests wolf populations are self-limiting, MacNulty said.
“There’s a perception that if wolves come into a new area, there will be no holding them back,” he said, “but ultimately what will be holding them back, if humans don’t, is themselves.”
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.
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. But what these wolves are ultimately limited by is the amount of space they have to raise their pups in safety.
–Dan MacNulty, USU ecologist
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.”
Read more at http://www.ksl.com/?nid=148&sid=29873051#Jt2mbQIpqIVSvXx6.99
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.
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. But what these wolves are ultimately limited by is the amount of space they have to raise their pups in safety.
–Dan MacNulty, USU ecologist
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.”
Read more at http://www.ksl.com/?nid=148&sid=29873051#Jt2mbQIpqIVSvXx6.99
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