Burroughs Backyard

Backyard biology from a field ecologist's perspective


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Rabbit tracking

When I woke up to snow yesterday morning, I was thrilled.  Part of my excitement was because I genuinely like snow – it lends a wintertime beauty to the landscape, a quiet to the woods, and the potential for skiing and snowballs.  But it was also because I’m part of a team working on New England cottontail research, and we need snow in the field to make our sampling worthwhile.  I dearly hope the snow sticks around through next week!

Why does rabbit research require snow?  Our work involves surveying thick, shrubby wetlands for rabbit pellets and collecting those pellets to be sent off for DNA analysis.  A day or two after snow, rabbits have had a chance to hop around, leave tracks, and lead us to pellets.  Furthermore, with snow on the ground acting as natural refrigeration, we know that the DNA within the pellets has been preserved, whereas it might have degraded under warmer conditions.  Finding brown pellets on brown leaf litter and mud is a lot more difficult than finding it on a bed of white snow.  And determining rabbit species identity from degraded DNA is hit-or-miss.

Believe it or not, there are two species of cottontail hopping around the eastern Hudson Valley, though most people wouldn’t know it – they’re all-but-indistinguishable by sight (which is why we do DNA analysis).  The New England Cottontail (Sylvilagus transitionalis) is New England’s only native cottontail rabbit.  But it’s not the one we generally see – that’s the Eastern Cottontail, native to much of the eastern United States but not present in New England until introduced there in the late 1800s.  Since then, the Eastern Cottontail has expended its range while the New England Cottontail’s populations have plummeted.  Part is from competition – the Eastern Cottontail is less timid than the New England Cottontail so will venture into fields, yards, and other less-shrubby habitat to feed.  This makes it more of a habitat generalist – a species that can live in a variety of habitats (and potentially in close proximity to humans).  This gives it a numerical advantage.  The other part is loss of habitat – New England Cottontails only live in thick, shrubby habitats (“thickets”), where they feel protected from hawks, coyotes, and other woodland predators.  These habitats are becoming rarer in the region.  Thickets form when a disturbed area (disturbed by fire, windblow, agricultural clearing, or any other reason) is regenerating from a field to a forest.  Naturally (in an ecological time scale), these habitats persist for 20 years or so until trees mature and limit the number of shrubs that can live in the understory.  New disturbances are what maintain the overall abundance of these habitats in the wild.  But humans prefer things to be a bit more static – fields are often maintained as fields and forests are often maintained as forests – so there are fewer thickets available than there used to be.

Thus, despite their reputation of “breeding like rabbits,” New England Cottontails are under consideration for listing as an endangered species.

As wildlife technicians in the Department of Environmental Conservation, the monitoring of rare and endangered species in New York State falls under our charge.  The federal U.S. Fish and Wildlife Service (USFWS) regulates the listing and taking of endangered animals, but state DECs (or equivalents) are major players in making endangered species monitoring happen.  We participate in both national and regional monitoring efforts – some more hands-on than others – and help obtain information on the locations, populations, and statuses of these species.  We also perform work to help the USFWS determine whether certain species warrant the special protection afforded by threatened or endangered status – without baseline monitoring of numbers, it’s hard to know whether a species is increasing, decreasing, or remaining the same over its range.  In addition, species that are “state endangered” – that is, rare enough to be endangered and protected in NY state but with a large enough population across the US to remain off the list of federally endangered animals – fall under the care of the DEC.

A decision on whether to list the The New England Cottontail as endangered will be made by early 2015.  In the meantime, we’re combing shrubby habitats for rabbit pellets to determine how many seemingly-appropriate habitats are actually utilized by these rare rabbits.  We focus on state-regulated wetlands, because they already have a level of protection that many habitats in the state lack.  Native wetland shrubs such as red osier dogwood, grey dogwood, nannyberry, swamp azalea, and highbush blueberry (to name a few) can make the thick, shrubby understory that lets New England Cottontails feel protected.  Wetlands also host a number of non-native shrubs – multiflora rose, privet, barberry, and Japanese honeysuckle, to name a few – that give bunnies a similar cozy feeling.  It seems a bit ironic that non-native shrubs might help create the habitat qualities needed to maintain a rare species.  In addition, powerline right-of-ways and native laurel patches might provide appropriate habitat.

On-the-ground, it’s never much fun to crawl through “rabbitat.”  If you remember from your childhood fables, rabbits do well in “br’ier patches” that other critters have trouble navigating through.  Such as humans.  Luckily I get to wear insulated coveralls – they keep me warm and make most of me impermeable to roses, blackberries, and barberry.  Despite the thorns, when one of us comes across a pile of “golden pellets” there’s jubilation.

More information:
USFWS pages on New England Cottontails: http://www.fws.gov/northeast/indepth/rabbit/index.html
FAQs: http://www.fws.gov/northeast/indepth/rabbit/pdf/NE_Cottontail_FAQs.pdf