Striving for a cottontail comeback

            Rhode Island’s only native rabbit, the rare New England cottontail, is on the verge of a modest comeback thanks to a complex conservation program led by a team of South County biologists. Once common throughout the region, the species had declined precipitously in recent decades because of habitat loss, hunting, and competition with the introduced eastern cottontail.

            “The rabbit that people see everywhere all the time is not our native cottontail,” said Cindy Corsair, a biologist with the U.S. Fish and Wildlife Service based in Charlestown, who supports the captive breeding of New England cottontails at Roger Williams Park Zoo and their release throughout the region. “New England cottontails have been impacted by the loss

of early successional habitat – scrubby, brushy thickets – whereas eastern cottontails are more of a generalist, more adaptable to a wider variety of habitat options.”

            To boost their population, New England cottontails that have been raised in captivity are released into what Corsair calls an “acclimation pen” at Ninigret National Wildlife Refuge in Charlestown, a one-acre fenced area where they are protected from predators and exposed to their native habitat.

            “When they’re at the zoo, they have it good – they’re in a safe, cushy cage and their food is delivered,” Corsair said. “We want them to get used to foraging a natural diet and learn to evade predators and other threats before being released. Ninigret is the perfect place for that because it has very high-quality habitat and accessibility for staff to monitor them.”

            Figuring out where to release the animals after their stay in the acclimation pen is largely determined by their genetics, a project undertaken by T.J. McGreevy, an assistant research professor at the University of Rhode Island.

Because the native and non-native cottontails are nearly identical, he first conducts a genetic analysis of the rabbits to make sure that those brought to the zoo for breeding are the target species, and then he confirms their gender. To reduce the chance of inbreeding in the wild, he does a similar analysis of the offspring so males and females from the same litter are not released at the same site.

“Genetic diversity is the raw material that natural selection can act upon,” said McGreevy. “The more diverse the population is, the better they can respond to diseases and other pressures. It helps with their fitness.”

McGreevy also supports region-wide efforts to find existing wild populations of New England cottontails. He analyzes the genetics of about 3,000 fecal pellet samples collected by volunteers and biologists each year to determine if they are from New England cottontails or eastern cottontails. Using this process, new populations of the native species were discovered this year at two sites in South County, including the John H. Chafee National Wildlife Refuge in Narragansett.

Since McGreevy knows the genetics of every New England cottontail released in the area, he can determine if the animals are reproducing in the wild by examining the genetics from fecal pellets collected at release sites. That’s how he confirmed that the cottontails are breeding at the Great Swamp Wildlife Management Area in West Kingston.

“We look at the fecal samples to see if it’s a genetic match to one we released there or if it’s a combination – half from two different animals,” he said. “That’s how we documented breeding at the Great Swamp.”

Dylan Ferreira, a wildlife biologist for the Rhode Island Department of Environmental Management, oversees the cottontail releases at the Great Swamp. He said that 17 animals were released there last year, but all were killed by predators.

“Predation is the limiting factor; it’s tough to get a population of New England cottontails to sustain itself because of so much predation,” he said. “It happens year-round – mostly by hawks, foxes and coyotes – but the rabbits have the best chance of surviving if we release them in summer when the vegetation is densest.

“If we don’t flood the area with rabbits, we don’t have much of a chance at sustaining a population because of predation,” Ferreira added. “You don’t want to spread them too thin or they’ll be gone in no time. It’s a tightrope we have to walk – do we put all our eggs in one basket or spread them out.”

Ferreira also manages a breeding colony of New England cottontails on Patience Island in Narragansett Bay. About 50 cottontails from that colony have been released at sites in Rhode Island, New Hampshire and Maine.

According to Corsair, another breeding colony is being established this year on Nomans Land, a small island near Martha’s Vineyard. And a new national wildlife refuge, called the Great Thicket, is being created in parts of southern New England and New York to provide more habitat for New England cottontails and other species that prefer similar terrain.

“Things are going really well so far,” Corsair said of the New England cottontail conservation effort. “There are so many eastern cottontails on the landscape that detecting New Englands is like finding a needle in a haystack. But we’re finalizing site selections for our next releases and coming up with monitoring plans for those sites. So we’re continuing to make progress.”

This article first appeared in the summer 2019 issue of the Shore Times.