Thursday, July 28, 2016

Yellowstone Science looks back at 20 years of wolves

Posted: July 20, 2016
A wolf pack in Yellowstone National Park works together to capture a bison. Utah State University’s Department of Wildland Resources and Ecology Center researchers and Yellowstone National Park scientists reported findings from a study on wolf packs and hunting on the PLOS ONE website, the peer-reviewed Public Library of Science online publication. Daniel Stahler / Courtesy of National Park Service
Yellowstone National Park released its latest Yellowstone Science publication last week, which takes an in-depth look at the 20-plus years since wolves were reintroduced.

The issue includes research findings and articles on wolf genetics, predation habits, infectious diseases that have struck wolf packs over the years, and even a section on “why wolves howl.”

“The restoration of wolves to the Yellowstone area was a transformational event because it completed the restoration of native, large carnivores in the ecosystem, which is a remarkable, though controversial, achievement,” said P.J. White, the park’s wildlife and aquatic resources branch chief.

Some 41 wolves from Canada and northwest Montana were brought into the park between 1995 and 1997. They have since been the focus of much controversy between wildlife advocates and hunters and ranchers — and gone through many delisting, and relisting, efforts over the years under the Endangered Species Act.

“It’s complicated,” wrote Yellowstone wildlife biologist Doug Smith in an introduction to the issue. “Everything with wolves is that way. Most people rate wolves among the most controversial wildlife to live with; a colleague from India rates them as more controversial than tigers — a species that occasionally kills people.”

Here are a few takeaways from the issue:

1. Wolf population growth has leveled off. Since reintroduction, scientists put the wolf population growth into two phases. In phase one, their numbers grew rapidly each year, reaching more than 170 in the park in the mid-2000s. After 2008, the second “saturation” phase began, where numbers have mostly hovered around 100 in the park.
Disease, limited habitat space, and an equilibrium between wolf numbers and those of their prey may have contributed to population size leveling off, scientists wrote.

2. Scientists know a lot about wolf genetics. Researchers write that “few non-human species have been at the frontiers of genetic research as have wolves and their relatives.” Genetic research was crucial when the wolves were reintroduced: Scientists carefully selected certain wolves from different packs in different parts of Canada to make up the new Yellowstone population.
Today, scientists collect genetic material each time a wolf is captured to be radio-collared, extracting DNA from the blood, tissue or scat. They are using the resulting information to study everything from genetic lineages of Yellowstone wolves, to wolf coat color and aggressive wolf behaviors.

3. Wolves are only so-so hunters. Previous research has shown that wolves often struggle to catch the ungulate they are teaming up on — whether it’s a moose, bison or deer — a fact that runs contrary to the popular view that wolves are some of the most savvy, and successful, hunters around.
It turns out wolves usually are only able to kill young, old and debilitated animals, scientists said, “a small fraction of the total prey population.” Many of their skeletal features, including their front teeth, their skulls and their long snouts aren’t that great for killing, researchers wrote.

To read the full Yellowstone Science issue, go to


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