Trapped in a steel cage barely big enough to hold her, the large squirrel was not happy, pawing at the bars and trying them with her teeth. Matt Whitbeck and Cherry Keller of the U.S. Fish and Wildlife Service were glad to see her, though. The furry gray prisoner, released after being weighed and checked, offered yet another sign that the Delmarva Peninsula fox squirrel, once vanishingly rare, has come back.

This supersized, reputedly shy member of the squirrel family now is considered fully recovered, according to federal wildlife officials. Confident the animal is back to stay, they plan to take the first step soon to lift all legal protections for it, something that hasn't happened much since Congress passed the Endangered Species Act 40 years ago.

"We're pretty excited about it. It's huge," said Whitbeck, a wildlife biologist at Blackwater, as he prepared to make an annual spring check of the Delmarva fox squirrels in the sprawling refuge south of Cambridge in Dorchester County.

"It's a neat, unique citizen of the Eastern Shore - it's something to be proud of," said Keller, an endangered-species biologist in the service's Annapolis office. She's spent the past 15 years overseeing efforts to restore the squirrel, but still considers it something of an enigma.

From a distance it might be hard to tell the Delmarva fox squirrel from the nosy, noisy familiar to most urban and suburban dwellers. The Shore native can be nearly twice as large as its common relative, reaching 30 inches in length, with half of that tail. It's a bit slower, and quieter, too, biologists say. That lack of chatter is part of the reason why scientists say they can walk through a forest they know harbors the animals and often not spot any.

One of 10 subspecies of fox squirrels found around the country, this one lives in trees like other squirrels, but it's somewhat less acrobatic and spends a fair amount of time foraging on the ground. It seems to do best in mature forests of hardwood trees and loblolly pines, especially when they border farm fields planted in corn - all of which still are fairly abundant on the rural Eastern Shore.

But in the first half of the last century, everything seemed to be going against the squirrel. Clearing of forests for farming, timber harvests and hunting all conspired to decimate its numbers. By 1967, when federal officials first listed it as endangered, the squirrel could be found in just 10 percent of the places it once frequented. Blackwater, with more than 28,000 acres of marsh, woods and water, was home to most of the survivors.

Since then, state and have labored to rebuild the population, reintroducing the squirrels to wooded areas where they were known to have roamed at one time. Eleven of those 19 "translocations" took, including nine on Maryland's portion of the peninsula.

Many of the relocations were to privately owned forestland, recalled Glenn Therres, who directed recovery efforts for the Maryland Department of Natural Resources. Owners agreed to take anywhere from five to 42 squirrels, he said, and they were not prevented from harvesting their timber, though they were required to leave 15 percent to 25 percent of it untouched for the animals.

"In that way, the squirrel never became a true liability to landowners," Therres said.

While landowners often believe having an endangered species on their property will prevent them from doing anything, Therres said that's just not so. Still, he acknowledged it may no longer be possible in today's political climate to reach the informal "handshake" agreements that cleared the way for squirrel relocations decades ago.

"We could have prevented the fox squirrel from becoming extinct by sustaining it on Blackwater refuge and on state lands," he said, "but we could not have recovered it without private lands."

It helped that the timber industry on Delmarva has changed over time, federal and state biologists say. Where landowners once focused on raising trees for paper production, they now cultivate them for lumber, which means trees can grow larger before being harvested, providing more habitat for the fox squirrels.

Hunters also have shifted their sights from squirrels to deer. And bow hunters, who often spend hours perched on stands in trees waiting for their quarry, have provided biologists with additional sightings and accounts of squirrel behavior.

Even so, the recovery has taken time. Whitbeck called the squirrels "homebodies" unlikely to roam far, which has meant they've only gradually expanded their territory from where they were transplanted.

That stay-at-home tendency is part of the animal's enigma, Keller said. Individual squirrels have been tracked for miles, but many others seem content to stay put.

"That's the thing - are they this elusive silvery gray ghost in the woods?" she said, with a laugh. "Or are they this bumbling fool on the edge of the road?"

"They seem to fill both models well," Whitbeck agreed.

The two Delmarva fox squirrels caught in traps checked one recent morning were both repeat customers, as indicated by the microchips detected under their skin. One has been trapped every year since 2010, Whitbeck said, and the other has shown up every other year since 2007 - remarkable for an animal that normally lives four to five years.

Could it be they're not smart enough to realize the danger, or clever enough to remember they can get a free meal of corn in the cage and suffer no real harm? Whatever the case, over time they've spread out to where they now cover 28 percent of Delmarva, and more sightings come in every year. Wildlife officials estimate there are 17,000 to 20,000 Delmarva fox squirrels on the peninsula, and believe now that their habitat is sufficiently protected to ensure that the species has a promising future.

Not everyone is convinced. Noah Greenwald, endangered-species director with the Center for Biological Diversity, said that while he's glad the squirrel has come back, he believes it "premature" to declare victory.

The environmental group would support a more gradual easing, he said, by "down-listing" or reclassifying the squirrel as threatened, a less severe status.

"But given the ongoing threats from urban sprawl and sea-level rise," Greenwald added, "it doesn't make sense to remove protections altogether."

Keller said sprawl and sea-level rise, which is expected to inundate much of the Blackwater refuge, could put a serious dent in the population, but federal biologists have concluded neither would threaten the species' survival. State laws, land acquisitions and easements on private land mean much forestland is preserved, and the squirrel has spread into areas less vulnerable to rising waters.

The wildlife service is preparing to formally propose de-listing the squirrel, possibly as early as this summer, Keller said. A final decision will be made after receiving public comment and further reviewing the situation. Even then, she explained, plans are to continue monitoring the population.

The 's recovery is evidence that the often-controversial can work, said Joe Roman, a researcher at the University of Vermont and author of a recent book on the law's application. De-listing doesn't happen often, he pointed out, and experts believe that the vast majority of listed species have such small numbers or so little viable habitat left that they'll need constant help to survive.

There are more than 600 animals listed as endangered or threatened and hundreds more proposed or candidates for listing, according to an online "box score" kept by the . Only 20 have recovered enough to be taken off the list, such as the bald eagle - though it still enjoys legal protection under different laws.

"We're looking for success stories," Roman concluded. "If the Delmarva is one of them, I think wildlife biologists would be happy to have it."

Delmarva fox squirrel

Habitat: Farms and forested areas of Delaware, Maryland and Virginia, including Blackwater National Wildlife Refuge, Chincoteague National Wildlife Refuge and Prime Hook National Wildlife Refuge

Status: Listed as endangered in 1967

Description: Gray coat, short rounded ears; can grow up to 30 inches long

Of note: Spends much of its time on the ground instead of in trees; quieter than most squirrels