The predators were poisoned and trapped to near-extermination in the United States last century, but have since clawed their way back to some of the most remote wilderness in the lower 48 states.
That recovery was boosted in the 1990s by the reintroduction of 66 wolves in Idaho and Yellowstone National Park. Yet as those first packs have flourished, increased livestock killings and declining big game herds have drawn sharp backlash from ranchers, hunters and officials in the Northern Rockies.
But biologists with the Arizona-based Center for Biological Diversity want to expand that recovery across the country. A few isolated pockets of wolves, they say, are not enough.
"If the gray wolf is listed as endangered, it should be recovered in all significant portions of its range, not just fragments," said Michael Robinson, who authored the petition. Robinson said the animals occupy less than 5 percent of their historic range in the lower 48 states.
The federal Administrative Procedure Act allows outside parties to petition the government to act when species are in peril. U.S. Fish and Wildlife Service spokesman Chris Tollefson, whose agency received the petition, said there was no deadline by which the agency must respond to the one filed Tuesday, which was signed by Robinson and another biologist, Noah Greenwald.
Tollefson also said an internal review was under way to figure out where wolves once lived and where they might be returned.
"We need to look at what is realistic and where the suitable habitat would be," Tollefson said.
The review will be completed by late 2010 or early 2011 and will contain recommendations but no final decision on whether to create new wolf populations, Tollefson said.
About 6,000 wolves live in the U.S. outside Alaska, with most of those in the Great Lakes and Northern Rockies, with only a few dozen in Arizona and New Mexico. They are listed as endangered except in Alaska, Idaho and Montana.
In early 2008, a similar petition was lodged by the Natural Resources Defense Council. In its rejection of that petition, the Fish and Wildlife Service said the Great Lakes and Northern Rockies programs had succeeded and any additional recovery efforts would be "discretionary."
The Fish and Wildlife Service faces no deadline to respond to such petitions
Like the Bush administration, the Obama administration has pushed to end federal protections for wolves and return control over the animals to the states.
But both administrations have been rebuffed in the courts. Federal judges have ruled repeatedly that the government failed to prove existing wolf numbers will ensure the population's long-term survival.
Last year, the Interior Department relented to pressure from environmentalists in the Great Lakes. The agency agreed to put wolves back on the endangered list at least temporarily - just months after they had been removed for the second time in recent years.
Wolves are notorious predators with a hunger for livestock, and experts say they could survive in most of the country if they were allowed.
Young adult wolves sometimes travel hundreds of miles when looking to establish a new territory. In the last several years, packs have gained a toehold in parts of Oregon and Washington. Others have been spotted in Colorado, Utah and northern New England.
But with wolves, more than just biology is at play. Politics serves the deciding role in where wolves are allowed, said David Mech, a wolf expert and senior scientist with the U.S. Geological Survey.
"In the areas where they are not acceptable, they will be killed out - illegally if nothing else, Mech said.
The Northern Rockies population has stirred the most rancor, largely because of sheep and cattle killings and wolves preying on big game herds that had swelled when the predators were absent.
Idaho and Montana initiated public wolf hunts last year, and both intend to increase their quotas on the animals this fall. The states want to put a dent in the animal's population growth rate, which has been as high as 30 percent annually.
Wyoming, which has about 525 wolves, was blocked in its efforts to start a hunt after federal officials said state law was too hostile to wolves to ensure their survival. That ruling has been challenged in federal court.
Wyoming House Speaker Colin Simpson said Tuesday it should serve as a warning for other states that are asked to take wolves.
"Be careful," Simpson said. "We don't need more of that in the West."
(This version corrects name of federal law that allows for outside party petitioning to Administrative Procedure Act, not Endangered Species Act.)