Now we know what happens to the trees, greens, microbes, humans and intertidal zones in the cold winter. I bet you're dying to know, what happens to bunnies in the winter? Well, winter is hard on the bunnies. Here I'll discuss a few of things I've learned while researching New England cottontail habitat.
New England cottontails are a species in decline, and they are a candidate species for the Federal Endangered Species List . This decline is thought to be largely due to habitat loss and fragmentation. Their range has contracted dramatically since the mid 1900’s: In 2004 it was found that New England cottontails occupied about 14% of their historic range . In order to conserve the species, many people, agencies, and non-profit organizations are interested in creating and maintaining more habitat for New England cottontails. Habitat for New England cottontails is very dense, shrubby vegetation that protects them from predators and provides abundant vegetation for them to eat. Coastal shrublands, abandoned fields, shrub wetlands, and early successional forests can all be habitat for New England cottontails.
How suitable a habitat is in the winter is very important for the survival of these rabbits. Like for many other animals, food for New England cottontails in the winter is limited, and they don’t get to migrate, or turn white like the snowshoe hare for camouflage.
Studies on New England cottontails have found that they have a low winter survival rate, and that the survival rate is heavily influenced by the habitat they find themselves in. One study compared New England cottontails in small (<2.5 hectares) and large (>5 hectares) habitat patches. The rabbits in the small habitat patches had a winter survival rate of 35%, compared to 69% for the rabbits in the large patches. 
New England cottontails prefer to eat nutritious food in an area where they are protected from predators. In winter, they browse on small twigs, buds and bark . Rabbits in small patches run out of good winter food that is in a safe area more quickly, so they must forage in areas where they are more vulnerable to predators, and/or starve. Their fur contrasts with the snow and they are relatively defenseless, so they rely on dense vegetation for protection at all times.
So, if you want more rabbits, increasing their winter survival rate is a good place to start. There are at least two approaches being taken to do this. One is creating large tracts of very good habitat that have abundant food in and around safe places to hide. The other is bringing food to the rabbits so that they don’t have to leave safe areas to forage. While not a long term solution, I think the latter method might be appropriate for certain situations. For example, small local populations that are declining might benefit from supplemental food while we work on improving their habitat for the future. A preliminary study with cottontails showed that supplemental winter food was associated with much higher survival rates ! This suggests to me that increasing the availability of forage, natural or supplemental, could have significant benefits for New England cottontail populations.
Like many organisms, winter means hard times for the New England cottontail. For them, the protection and food provided by their habitat in the winter is critical.
1. Litvaitis, J.A., et al., A range-wide survey to determine the current distribution of New England cottontails. Wildlife Society Bulletin, 2006. 34(4): p. 1190-1197.
2. Barbour, M.S. and J.A. Litvaitis, Niche dimensions of New England cottontails in relation to habitat patch size. Oecologia, 1993. 95(3): p. 321-327.
3. Litvaitis, J.A. and W.J. Jakubas, New england cottontail (Sylvilagus transitionalis) assessment, M.D.o.I.F.a. Wildlife, Editor 2004: Bangor, ME.
4. Weidman, T. and J.A. Litvaitis, Can supplemental food increase winter survival of a threatened cottontail rabbit? Biological Conservation, 2011. 144(7): p. 2054-2058.