Research Investigates Species Decline
Not all rabbits multiply like--rabbits.
In fact, the New England cottontail is having a tough time of it. A hundred years ago the species accounted for 100 percent of the regional cottontail population. Today it makes up a mere 8 percent, outstripped by its more prolific relative, the eastern cottontail.
Things have gotten so bad for the New England cottontail that it’s a candidate for protection as an endangered species, according to Associate Professor of Biology Randall Tracy, Ph.D. He has yet to find a New England cottontail in Worcester County after three years of research.
Working closely with the Mass. Department of Fisheries and Wildlife, Tracy and a small group of student researchers have been searching for the elusive creature in various woodlands using non-invasive traps and cameras equipped with motion sensors. The researchers bait and set traps in the evening, tucking in some leaves so any captured animals can stay warm. Early the next morning, they return to catalog the species and gender of animals in the traps before releasing them.
“My research focuses primarily on the distribution and abundance of small mammals.” he explained. “We want to understand why certain species are in decline and understand what it is about certain environments that allow them to live there.”
Scientists believe that one reason for the decline of the New England cottontail is its metabolic rate—the speed at which an organism converts food to tissue. “The eastern cottontail has a higher metabolic rate,” Tracy said. “The many abandoned farms in the region provide high quality, abundant forage, which fuels its rapid reproduction. The New England cottontail, on the other hand, has a slower metabolic rate. It doesn’t reproduce as quickly, but it is better equipped for hunkering down and surviving in marginal habitats.”
He explained, “The New England cottontail evolved during the last Ice Age, when its low metabolic rate may have been an advantage. It’s the woolly mammoth of the rabbit world.”
This “woolly mammoth” was relatively secure until the early 20th century when game clubs introduced the eastern cottontail to New England to increase the rabbit population. Prior to that, its northernmost range was the Hudson River Valley. The two species—which have a different chromosome count and don’t interbreed--had never before competed for the same habitat.
To casual observers, the decline of the New England cottontail may not seem significant, since the two species look remarkably alike. The New England cottontail is distinguished by a black patch of fur between the eyes and along the edge of its ears, while its close relative has a white blaze between the eyes (even one white hair counts). “Their close resemblance has worked against placing the New England cottontail on the endangered species list, since hunters are not able to identify it from a distance,” Tracy noted.
Still, he said, it is important to try to preserve the species to maintain biological diversity.
Tracy has conducted similar lines of research on the southern bog lemming, a hamster-like mammal that faces competition from the meadow vole. The last recorded sighting of a lemming in Worcester County was the 1950s—that is, until Tracy, Associate Professor of Biology Steven Oliver, Ph.D., and student researchers discovered one last summer.
“It was very exciting to find living proof that they’re still in the area,” said Tracy. “But even when we don’t find what we’re looking for, our research reveals a lot about what is going on in a particular habitat.”
He added, “When we think about biological diversity, we tend to think about the rain forest. But it’s important to maintain diversity in our own back yard. We don’t want the New England cottontail to go the way of the woolly mammoth.”
Worcester Statement, spring 2009