This winter, our science department is attempting to document if a rare and elusive species of cottontail rabbit is still present on Nantucket. The New England Cottontail (Sylvilagus transitionalis) is the only cottontail rabbit that is native to the northeastern United States. It prefers dense shrubland habitats where it can effectively hide from predators, and for this reason is rarely seen. The more common Eastern Cottontail (Sylvilagus floridanus), which looks virtually identical to the New England Cottontail, occurs in shrubland habitats as well, but also frequents open grasslands, suburban yards, parks, fields and pastures. Because Nantucket was mostly open grassland habitat during colonial times due to extensive sheep grazing, New England Cottontails were probably never numerous. Therefore, the Eastern Cottontail was introduced in the late 1800’s to provide game for hunters. This species has since become the predominant local rabbit and is extremely common. The last recorded incidence of a New England Cottontail on Nantucket was a hunter’s specimen received by the Massachusetts Division of Fisheries and Wildlife (Mass Wildlife) in the late 1990’s, but no systematic inventories have been conducted.
The U.S. Fish and Wildlife Service (USFWS) has placed high priority on locating sites where there are still viable populations of New England Cottontails due to concerns regarding drastic declines across their range. Habitat loss has likely played a factor in these declines; however, it may also be lack of information about the population status of this secretive species. Nantucket has been identified as one of the most likely sites where remnant New England Cottontail populations may still exist. This is because they were known to have once occurred here and there are vast expanses of highly suitable, undeveloped habitat currently available – most of which is on property owned and protected by the Nantucket Conservation Foundation.
We began searching for this species last winter, when Karen Beattie and Danielle O’Dell from our staff were trained by USFWS biologists to conduct trapping and tissue sampling at the Mashpee National Wildlife Refuge, where New England cottontails currently occur. Once we obtained permitting from the Mass Wildlife, we set out “Havahart” live rabbit traps baited with apples in suitable habitat on Foundation-owned properties. DNA analysis is the best way to definitively distinguish between the two cottontail species. Therefore, a pin drop of blood and a small tissue sample is taken from the ear of each rabbit captured and submitted to the University of Rhode Island and the University of New Hampshire for analysis. Each rabbit is also tagged with an individually numbered ear tag, weighed and various other body measurements are taken.
We spend a great deal of time trapping on our properties at Sanford Farm, Ram Pasture, Coatue, the UMass Nantucket Field Station, and South Pastures (the area south of Milestone Road on the eastern end of the island). However, we were only able to capture a total of 14 rabbits over the course of the winter. This was likely because rabbits are not likely to enter a suspicious-looking trap unless they are extremely hungry, and the mild winter weather last year resulted in plenty of available food. Two of these captures were snow shoe hares, which were also historically introduced to the island as a game species. DNA analysis of blood and tissue samples collected and submitted indicated that none of the remaining 12 samples were New England Cottontails.
So this year, we are rethinking our strategy and modifying our methodology to obtain more samples in a shorter period of time. Another way to obtain DNA samples that can be analyzed is to collect fecal pellets (aka bunny poop). The best field conditions for doing this are when there is fresh snow cover. This ensures that the sample is relatively recent and also insulates it from the ground and anything that might contaminate it with the DNA of something else. Samples are collected using sterilized tweezers and stored in small vials filled with Ethanol. This methodology was not utilized last winter because we only had one very brief and limited snowfall event. Fortunately, this has been a good winter for lingering snow, and our staff is out there searching for fresh pellets whenever the conditions are appropriate.
There is one additional way that New England and Eastern cottontails can be differentiated: skull suture patterns. Skull sutures are junctions between the major bones of the skull. In New England Cottontails, the skull suture lines between the frontal and nasal bones of the skull are irregular and jagged, while those of the Eastern Cottontail are smooth. Also, the auditory bulla (the hollow, bony portion of the skull that encloses portions of the inner and middle ear) is smaller on New England cottontails as compared to Eastern Cottontails. Needless to say, these differences are not helpful in identifying individual rabbits in the field. But if you happen to be a rabbit hunter and are interested in “donating” the intact head of any rabbits you harvest, the NCF Science and Stewardship Department would gladly accept your contributions – just store each specimen in an individual Ziploc bag (with the date and specific location where the rabbit was harvested recorded with permanent marker on the outside) and freeze it while it is still fresh. We will happily collect your specimens and store them until we are able to get them transferred to a game biologist at the Mass Wildlife for identification. Please call our office at 508-228-2884 and ask for any member of the science staff for more information.
So…….why are we so interested in finding out if New England Cottontails are still on Nantucket? Firstly, one of the goals set out for our science department by the Foundation’s Board of Trustees is to “protect natural communities and species found on Nantucket, especially those that are threatened or endangered.” New England Cottontails and the shrubland habitats they prefer are both considered threatened or endangered on a region-wide basis. Knowledge of their presence and the locations of population concentrations will enable us to better manage the habitats where they occur. Also, grant money may be available for conducting habitat management efforts in areas where New England cottontails are known to occur. Funded projects are aimed at preventing shrublands from succeeding into forests, which are less suitable for New England cottontails. If we are successful in documenting the presence of this species on Foundation-owned lands, it is possible that we will be eligible for grant funding to conduct habitat management work that will benefit this rare species, as well as others such as northern harriers, eastern whip-poor-wills and several species of rare shrubland-associated moths. Furthermore, such management would concurrently enable us to achieve some of the goals identified in our Wildland risk reduction initiative (see related Blog posted on December 7, 2012), as preventing shrublands from turning into forests will also benefit hazardous fuel reduction efforts.
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