MASHPEE — When the order from the burn boss came over the radio, a colleague torched a patch of low-lying twigs in the Mashpee National Wildlife Refuge, igniting a blaze that swept through 10 acres of pitch pines and scrub oaks.
The fire consumed everything in its path but the scattered trees, leaving a bed of fertile ash and enough open space for the sun to reach the ground again, allowing growth of a new forest to begin.
The controlled burn last month on Cape Cod was part of a multimillion-dollar effort by federal and state agencies to rebuild the dwindling habitat of the New England cottontail, which lives in the dense bramble found in new forest growth. Over the past 50 years, the bark-colored rabbit has lost nearly 90 percent of its dwelling areas to development, which has wiped out most of the region's young forests.
The rabbit, which has perky ears and a tail that looks like a puff of cotton, is the only animal from New England that federal officials are now considering as a candidate for the nation's list of endangered species. To avoid granting that rare designation (the protection provided by endangered status would create an expensive regulatory burden for developers and the government) federal and state officials have already spent $24 million and plan to spend tens of millions more to rebuild the population of the native rabbits, which for millennia inhabited the region in large numbers.
The expense is necessary, biologists say, because the rabbits play an important role in the ecosystem and represent the unique biodiversity of the region. The work to protect them also benefits scores of other animals who share the same habitat.
"If we allow the species to blink out, then it's just a matter of time before we become concerned about another species," said Anthony Tur, an endangered species biologist and director of the New England Cottontail Initiative, an effort by federal and state agencies to save the rabbit. "At some point, we have to draw the line. How many species should we be willing to lose before we do something about the problem? For the Endangered Species Act, the tolerance is zero."
No one knows precisely how many cottontails remain in New England but wildlife biologists believe they have vanished from Vermont and dwindled to several hundred elsewhere.
Those remaining live in patches of young forests spread like islands over a few thousand acres across New York, Connecticut, Rhode Island, Maine, New Hampshire, and Massachusetts. They used to be found in every part of Massachusetts but now live only in Eastern Cape Cod and parts of the Berkshires.
Unlike other rabbits, the native cottontails rely on the low-lying shrubs of young forests for food and protection from predators, such as raptors, owls, coyotes, and foxes. Much of the area's remaining forests have matured and are no longer suitable habitats.
The at-risk rabbits haven't adapted like the similar-looking, nonnative, and far more abundant Eastern cottontails. Those rabbits, brought to the region by trappers in the 19th century, flourished because they have better peripheral vision than the native bunnies, allowing them to hop to safety more quickly and thrive in less-forested areas.
With the right conditions, wildlife biologists say, they could repopulate quickly. They can breed before their first birthday and females have two to three litters a year, ranging from three to eight bunnies at a time. They may also benefit from climate change, as warmer winters might mean more food, cover, and better camouflage.
With a decision awaiting next year on whether the rabbits should be added to the endangered species list, federal and state officials have developed a detailed plan to foster a rebound.
That includes not only controlled burns, to spur the growth of shrubs, but also a captive breeding program at the Roger Williams Park Zoo in Providence. Officials there have succeeded in rearing and releasing 81 rabbits into the wild since 2011, said Lou Perrotti, the zoo's director of conservation programs, noting that 60 percent were found to be thriving.
Federal and state officials are also working with landowners who have volunteered to have their property transformed into better habitats for the rabbits.
Since 2010, Ted Kendziora, a wildlife biologist, has worked with more than a dozen landowners to improve at least 1,000 acres. "You have to explain to people the beauty of [a young forest] and why it's like a shopping mall for the cottontail and over 70 species of animals, allowing them to find food and meet their mates."
He said cutting down trees to benefit the environment is counterintuitive for a lot of people.
"I have to explain that it opens space and allows the understory to grow," he said, referring to the low-lying growth vital for the cottontails. "It's amazing how quickly we see a difference. As soon as we do it, you see the songbirds, rabbits, deer, black racer snakes, turkey — all kinds of animals — start to move in."
In all, federal and state officials are hoping to convert some 51,000 acres of land throughout the region into young forests by 2030, with the goal of spawning a population of nearly 30,000 New England cottontails.
The controlled burns on Cape Cod should bear results within a year or two, officials said. The charred wasteland left after the fires will soon see sprouts of huckleberry, blueberry, greenbrier, grasses, twigs, and other bramble to feed and protect the rabbits.
Said Marianne Piche, a habitat biologist with the Massachusetts Division of Fisheries and Wildlife: "The fire provides the light and space for them to germinate and give the cottontail what they need."