for National Geographic News
In the 11 years since gray wolves were reintroduced into Yellowstone National Park, they haven't seen a season as devastating as this.
According to park officials, 47 of the 69 wolf pups born last year have died. And though there's no official word on what's causing the deaths, experts monitoring Yellowstone's packs believe a dog disease called parvovirus is responsible.
Dan Stahler is a biologist at the park, which straddles the borders of Montana, Idaho, and Wyoming. He said further testing is needed to confirm that parvovirus is killing the pups.
"We won't know for sure until we can trap and test the animals this winter," he said.
Park officials are cautiously optimistic that this will be a temporary setback for the wolves, he added.
"We are not alarmed, but definitely concerned," Stahler said. "Our prediction is we will rebound."
A Constant Threat
Parvovirus, also known as parvo, spread from domestic dogs to wild animals in the U.S. in the late 1970s. Since then the disease has become an everpresent part of the wildlife environment.
"It's in the environment like fleas are in the environment," said Carolyn Sime, wolf program director for the Montana Department of Fish, Wildlife and Parks. "It is just out there and they can pick it up."
The virus is carried by a number of wild animals, including coyotes, foxes, and some wolves. It is highly contagious and is usually passed through contact with the feces of infected animals.
The virus can infect the small intestine, causing severe diarrhea, dehydration, and ultimately death. Pups are particularly susceptible.
Given that parvo is a constant threat, scientists don't know why it flares up in some years and not in others.
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