Appendix B
BUNNY HOPPININGS
By Peter G. Mirick
Peter G. Mirick is a wildlife biologist with the Massachusetts Division of Fisheries and Wildlife, as well as that agency’s talented writer and editor of publications. He is the author of numerous articles profiling various species found on Cape Cod. They’re well researched and enlightening.
I’ve chosen this article to share with you, which is aptly entitled “Bunny Hoppinings.” It’s extremely long for an appendix; however, I thought it important for us to examine one or two species in depth from the scientific vantage point of wildlife biology and its kin, conservation. That I’m passionate about rabbits probably factored into my decision to run this article. Mirick writes that our only native cottontail, the New England cottontail, has been “replaced” by the eastern cottontail, a nearly identical-looking species, all in the last fifty years.
It’s hard not to love bunnies. Everybody does: coyote, fox, fisher, mink, weasel, larger hawks and owls, big snakes, house cats, bobcats, domestic dogs and people. Not to mention any number of trematodes, cestodes, nematodes, lice, fleas and ticks.
Bunnies seem to have evolved as the ultimate prey: profusely abundant, fast reproducing, easily dispatched (once you catch them) and possessing a satisfying amount of nutritious meat. They are the daily bread of a thousand predators, a broad band in the upper foundational layer of temperate food chains across the globe. So popular are they that several species have been transplanted intercontinentally, allowing some to become invasive species that have significantly impacted the ecosystems into which they were introduced.
Here in the Commonwealth, we have only two native species, the New England cottontail, Sylvilagus transitiionalis, and the snowshoe hare, Lepus americanus. Neither could be said to be thriving. The New England cottontail has exhibited an extreme (>75 percent) decline in numbers and range over just the past few decades, largely replaced on the landscape by the introduced eastern cottontail, Sylvilagus floridanus. Its continued survival appears to be in imminent jeopardy, and it is now a candidate for federal endangered species listing. Meanwhile, the snowshoe hare, a northern mammal ideally adapted to boreal forest regions with cold winters and deep snow cover, could almost be a poster child for the wildlife implications of climate change. Maybe it’s time we give our Bay State bunnies a little more attention.
LAGOMORPHS
Cottontails, which are rabbits, should not be confused with hares, which are hares, and since people seem to have a predilection to use the terms interchangeably, and since both can be lumped under the vernacular “bunny,” we might as well set the record straight. Rabbits and hares are lagomorphs, meaning they belong to the Order Lagomorpha, which also includes a diverse family of exceptionally cute little furballs called pikas (none of which live in New England, unfortunately, but some of which, because they live in isolated alpine habitats or “sky islands” in the form of mountains from which they cannot depart alive, may already be critically endangered by climate change). Lagomorphs were once classified as rodents despite their unique dentition (in particular, a set of rounded “peg teeth” directly behind their upper incisors), and they were not taxonomically emancipated from the rats and mice until 1912. They may actually be more closely related to the primates than they are to the rodents.
Rabbits and hares share a number of obvious characteristics, including a high reproductive rate and long, independently controlled ears that offer superb directional hearing and also function as thermal radiators when their owners become overheated. They have a cleft upper lip that aids them in food manipulation. Their skeletal structure is evolved to handle the multiple g-force stresses of fast acceleration and sudden changes in direction when in full flight. Their hind legs are longer and much stronger than their front legs, and although they will use a digitigrade walking gait, their standard locomotion is a plantigrade hop.
They tend to be nocturnal, or at least crepuscular (active at dawn or dusk), and most have excellent vision. Their typically large eyes and narrow skull, somewhat reminiscent of the woodcock’s in design, allow them continual, nearly 360-degree monitoring of their surroundings—a very useful ability for animals that could accurately be labeled “universal prey.” When injured or captured, all of our lagomorphs are likely to produce surprisingly loud squeals full of heart-rending terror. Otherwise, they rarely make any noise at all other than some soft calls exchanged between mothers and young. This is to be expected in a nonsocial species; they just don’t have much need for auditory communication that could alert predators to their presence. Our lagomorphs do thump their feet when alarmed, however, and thus may altruistically alert nearby individuals to the approach of danger.
REFECTION
All three of our lagomorphs practice refection, a sort of “pseudo rumination” that allows them to extract maximum benefit from their food without having to carry the four stomachs of a ruminant around with them. They do this with the aid of a special food storage/fermentation vat of an organ called the cecum, located between the small and large intestines. The short version goes like this: the rabbit consumes bark and greenery, the stomach churns it and the small intestine absorbs whatever nutrients are present before squirting it all into the large intestine. The large intestine, which cannot absorb nutrients, separates the high-fiber, low-nutrient material from the high-nutrient, low-fiber material passing through it. The low-nutrient material is packed into hard pellets and deposited as waste, resulting in those familiar batches of “rabbit raisins” all outdoors people readily recognize. The high-nutrient material is sent back into the cecum, where bacterial action breaks it down into sugars, amino acids and other absorbable nutrients. Following fermentation, and always timed to be deposited during the animal’s resting period, the cecum squirts the wholesome mixture back into the large intestine, which packs it into special soft, greenish pellets, called cecotropes, and sends them out to be immediately re-ingested by the rabbit. The nutrients are then absorbed in the small intestine on the second pass. Thus, the animal acquires a number of precious nutrients and crucial vitamins that would otherwise have been lost as waste. It is quite a feat of bioengineering.
COTTONTAIL ISSUES
The most common rabbit in Massachusetts today is undoubtedly the eastern cottontail (EC), the one you see munching weeds in the backyard around sunset; the one that mowed through all your string beans and sprouting flowers overnight last May; but also the one that did not dig up your bulbs (because rabbits, unlike rodents, don’t dig up bulbs and shouldn’t be falsely accused of such shenanigans). It is now a ubiquitous mammal in Massachusetts, thriving wherever it can find a little cover and lots of low greenery (which pretty much describes suburbia). Most authorities believe the first ones stocked in the Commonwealth were released by hunters on Nantucket sometime in the last quarter of the nineteenth century.
Hunters loved the EC because, unlike the New England cottontail (NEC), which tends to “go to ground” immediately when pursued, this rabbit unusually runs, taking its pursuers on lengthy, circuitous chases. During the heyday of wildlife introductions in the first half of the twentieth century, more than 16,000 ECs were transported from the midwestern states and released here, and another 4,600 were raised at a MDFW game farm and released. Today, the EC can be found in every county of the Commonwealth and appears to greatly outnumber and hold more ground in all of them than the NEC, which is now extirpated from Dukes and Nantucket Counties and may already be absent from at least a couple others.
The EC now ranges over most of the continent below the Canadian border, but it appears to have evolved in the multitudinous edge habitats of the prairies and seems best adapted to mixed field/forest habitat. Conversely, the NEC appears best adapted to high-density thicket habitats, those that occur ephemerally following abandoned beaver ponds, forest fires, ice storms, tornadoes, hurricanes and flooding, to name a few. Thickets are areas with high stem density, and this appears to be crucial for NEC habitat.
High stem density areas where NECs may be found include young forests (regenerating after natural disturbances like those mentioned above, or after timber harvest); agricultural lands reverting to “old field” habitats; areas that have been mechanically cleared and are regenerating dense woodsy cover (such as power line cuts and railroad corridors); shrub swamps and brushy areas near beaver flowages; dense upland shrub thickets (composed of native shrubs, brambles and greenbrier); and coastal shrub-lands with frequent wind and salt spray.
It is unlikely that either species can live in contiguous, mature, closed-canopy forest; they both need open-canopy habitats, but one needs small openings, while the other can use any size opening. Civilization is prone to making big openings, and unlike nature, it doesn’t typically allow them to close up and reopen again.
EC VERSUS NEC
As John Litvaitis of the University of New Hampshire so eloquently demonstrated with his continuing research on the two species, the EC can pick up the airborne approach of a great horned owl at a distance of seventy feet, while the NEC, with its smaller, less effective eyes, doesn’t react until the predator has closed the gap to thirty feet. NECs seem well aware of their sensory limitations and do not venture beyond the edges of the high stem density habitats that have cradled them for thousands of years. The EC does not have this limitation, however. A habitat generalist, it is better adapted to fragmented forests and farmlands than its more specialized cousin, and it thrives in the mixed field/forest edges of suburbia. The NEC appears to require habitats of sufficient stem density and impenetrableness that predators are not cause for alarm unless they get within thirty feet.
Both species are frustratingly similar in their looks, habitats and behavior. They have two or three litters a year, from March or April through September, five to six young per litter. Like the snowshoe hare, they switch from a summer diet of grasses and leafy vegetation to a winter diet of bark, twigs and bugs. They can both jump ten to fifteen feet when they are in a hurry, and both can hit speeds approaching twenty miles per hour in a dash.
While home range sizes of up to forty acres have been reported, the latest MassWildlife biologist Jim McDonough, who conducted groundbreaking research on cottontails in the 1950s, found the average home range size was less than one and a half acres. He also found the NEC bred later in the spring than did the EC, but springs being what they are in New England, it is doubtful this provides the EC with any significant advantage over the NEC.
But something has tipped the scales; something has caused the formerly widespread native’s range to contract and become spotty, and the spots, based on the limited survey data available, to become smaller and in many cases to wink out altogether. The NEC’s range has shrunk by 86 percent, and some 60 percent of the spots or “habitat patches” where it still occurs are now considered population sinks. These are habitat patches with characteristics that drew in NECs from some other patch but are not of sufficient size or quality to maintain a local, productive population. Such poor-quality habitat patches “drain” the population rather than replenish it with new NECs.
In Massachusetts, the NEC was once found statewide. However, a survey conducted from 1990 to 1993 found NECs in only six counties. The EC was found in thirteen of fourteen counties. To our north, the situation is not any better. A 2008 New Hampshire survey found NECs in only nine of twenty-three sites where they were found in 2003, while Maine found NECs in only fourteen of eighty sites previously occupied in 2004.
Concerns about the NECs’ long-term population decline prompted the USFWS to propose the NEC as a candidate for listing under the U.S. Endangered Species Act. It is no surprise, then, that the NEC is identified as a “species of greatest conservation need” (SGCN) in the wildlife action plans of every state within the NECs’ range, including MassWildlife’s Comprehensive Wildlife Conservation Strategies (state wildlife action plan), which you can view online at www.mass.gov/masswildlife.
HABITAT IS THE KEY
The statistics on the NEC beg the question: What is causing this population decline? Just as “location, location, location” is the prime factor in real estate, “habitat, habitat, habitat” is the prime factor in supporting the NEC. John Litvaitis, a leading researcher of the NEC, has concluded that the loss of the species’ primary habitats to development, fragmentation and forest succession is its main problem. It would seem that for the NEC, natural nor have human disturbances created sufficient habitat to counteract these landscape changes and land practices.
Adding to the NEC’s problem, there is also evidence that the EC may be outcompeting the NEC for habitat. The NEC was known to use a much broader variety of habitats prior to the introduction and expansion of the EC population. This suggests that the EC outcompetes the NEC in most habitats except those with very high stem density (thickets). Since thicket habitat is of limited size and fleeting in duration, NECs must be able to move on to the next patch when the one they are inhabiting begins to mature into something else.
If the ECs already dominate much of the intervening habitats, then odds are good that NECs will have to travel farther—and traveling through unfamiliar territory is always perilous—in their search for new, higher-quality habitat where they will have more of an advantage. Even though captive trials indicate that neither species displays an advantage in physical domination of the other, the EC is likely more adaptable and competitive over a broader range of habitats, possibly due to its advantage in earlier detection of predators. Still, the NEC is vanishing from parts of its range where the EC is not present, so factors other than competition with the EC are involved.
Although not native to Cape Cod, eastern cottontail rabbits (Sylvilagus floridanus) thrive here. Courtesy of Heather Fone/HSUS.
One possibility is that invasive plants may be a contributing factor in the NEC’s decline. One of the few dietary studies on the two cottontails suggested that the EC is adapted to a wider variety of foods than the NEC. Is it possible, then, that the EC can feed on more of these aliens than the NEC? Have alien plans usurped so much of the habitat from native plants that the NEC can no longer feed its provincial tastes? Currently, we just don’t know.
MANAGEMENT AND SURVEYS
So what conservation actions can be taken to stem and reverse the downward trend of the NEC population and maintain viable and healthy numbers throughout the range of the species? Massachusetts, along with five other states (New Hampshire, Connecticut, Rhode Island, Maine and New York), is now working together with the USFWS and other conservation partners both public and private in the Rangewide New England Cottontail Initiative. The initiative is focused on creating and restoring 1,200 acres of NEC habitat by creating fifty new habitat patches across the species’ range. The target goal is to increase the NEC numbers by at least 720 animals and support a viable, long-term population. The Rangewide NEC Initiative is just gearing up to begin in 2010 and will use federal and state matching funds over the next three years.
In addition to this habitat initiative, Massachusetts and its partner states and organizations will be trying to address another challenge: how to survey for NECs and identify potential NEC habitat statewide. The root of the challenge is that there is no easy way to tell the difference between living NECs and ECs (although there are obvious differences in skull characteristics), so there is no way for biologists to solicit a voluntary army of observer/reporters to help us keep tabs on the situation (as we could with, say, robins, porcupines or even garter snakes). Unless you have the rabbit in hand, it is almost impossible to examine their often subtle external differences in sufficient detail to be certain of the species. About all you can tell at a glance is that if it has a white spot or blaze on the forehead, it’s an EC, not an NEC, all of which lack this marking. Unfortunately, the converse isn’t true, since about half of the ECs also lack this marking.
Fortunately, DNA testing of fresh pellets, like skull analysis, can be used to accurately distinguish between the two species. In the past, MassWildlife used skulls from roadkilled, injured, sick and harvested rabbits to survey our rabbit species. Most of the skulls were voluntarily collected and submitted to us by the public. The surveys were conducted in 1979, 1981, 1991–93 and 2000–3. Future efforts to identify and monitor NEC occurrence within Massachusetts and at specific management sites will likely involve both skull collections and DNA analysis of pellets. Other conservation efforts may include introductions of NECs from managed source habitats or supplemental breeding sites (such as the ones we attempted to establish on Grape Island in Weymouth in 1985).
One thing that will definitely be part of our NEC conservation efforts is the creation of thicket habitat, the young forest and shrubland, high stem density habitat that is not only critical to the conservation of the NEC but is also a host of other species, from insects to ruffed grouse to bobcats. This is where MassWildlife’s Forestry and Upland Habitat Program takes center stage. Among its primary goals for all forest lands controlled by the agency is to bring 15 to 20 percent of that forest habitat to a young age through active management and timber harvesting.
While active forest management through logging is sometimes controversial, it is necessary to maintain forest diversity—and forest is the primary habitat of New England. If we don’t conduct this kind of forest management, we risk losing the natural diversity of our native wildlife species. A quilt or mosaic should not be made of identical components, and neither should the New England forest. It is as simple as that. There is considerable incentive to increase the pace of young forest creation when the NEC seems to be disappearing so rapidly.
The NEC can be conserved on managed habitat (thicket) patches through timber harvesting, brush mulching, mowing and prescribed burning, which throughout its evolution were provided by the work of beavers, floods and forest fires. The NEC should, as the local species better adapted to the local (though now thoroughly fragmented) thickets, be able to hold its own in competition with the EC flatlanders in this specific habitat. The habitat patches will need to be a minimum of ten to twenty-five acres in size and ideally adjacent to or connected to each other so that animals can disperse safely between them.
Questions about the distances between patches and how they relate to NEC survival must be answered to understand how best to increase and support NAEC populations. As their ephemeral habitat is lost or degraded due to development, fragmentation and forest maturation, the NEC will continue to face many potential threats on a landscape that must be, to the NEC, an alien countryside the likes of which their evolution in New England could never have prepared them.
Stay tuned. The unfolding story of New England’s lagomorphs is far from over…