BILLINGS, Mont. — Black-tailed prairie dogs were denied protection under the Endangered Species Act on Wednesday after federal officials concluded the once prevalent species shows signs of rebounding.
Decades of poisoning, shootings, the plague and loss of habitat to agriculture are blamed for a dramatic drop in prairie dog numbers since the early 1900s, from roughly one billion animals to an estimated 24 million today.
In 2007, the New Mexico-based environmental activist group WildEarth Guardians petitioned the U.S. Fish and Wildlife Service to list the animal as threatened or endangered.
But the agency said Wednesday the population is slowly spreading despite continued pressure from sickness and deliberate killings.
"They reached a low point in approximately 1961 and have bounced back pretty good since then," said Joy Gober, the Fish and Wildlife biologist who drafted the decision.
A representative of WildEarth Guardians said a federal court challenge to the ruling was likely.
"Prairie dogs are still around but they are incredibly isolated and fragmented across 90 percent of their range," said the group's Lauren McCain.
Black-tailed prairie dogs — burrowing animals that reach a little over a foot long and weigh up to three pounds — once occupied an estimated 50,000 square miles and ranged across at least 11 Central and Western states.
Regarded by most farmers and ranchers as a nuisance, the animals are considered a keystone species among biologists. They are a primary food source for rare animals such as the black-footed ferret and their abandoned burrows serve as nests for owls.
Federal officials say the most common species of prairie dogs now occupy about 3,750 square miles within a range that stretches from Montana and North Dakota south to New Mexico, Texas and Arizona.
The denial of endangered or threatened status means the species will continue to fall under the watch of state wildlife and agriculture agencies, some of which classify prairie dogs as "pests" because they are thought to compete with livestock for forage.
U.S. Sen. John Thune, R-S.D., said the denial of new protections was appropriate for animals that "threaten livestock grazing lands and potentially harbor contagious diseases."
There are few restrictions on killing the animals except in Arizona, where the species was once wiped altogether. A prairie dog reintroduction effort was launched in that state in October.
Elsewhere, however, new threats may be emerging. Earlier this year, the Environmental Protection Agency approved the expanded use of a new prairie dog poison, Rozol, over objections from the Fish and Wildlife Service.
Environmental groups such as the Audubon Society have sued to repeal the approval.
Gober, the government biologist, said her agency's concerns centered on the poison's potential danger to predators including black-footed ferrets and eagles. At least one bald eagle and two badgers have been killed by the poison and more deaths have likely gone unreported.
"Anything that might eat prairie dogs is vulnerable," Gober said.