Once ranging throughout all the states of New England, the New England cottontail population has plummeted in recent years. Their range has dwindled by 75% and they can no longer be found in Vermont.

Researchers believe the decline is caused by the change in environment. New England cottontails thrive in young forests (forests 25 years old or less) that include a lot of shrubs and thickets. They also rely on interbreeding between cottontail populations in order to produce healthier, more genetically diverse offspring.

Unfortunately for New England cottontails, forests have been growing for 100 years after the decline of colonial agriculture in 1900, which means the shrubs and thickets have given way to trees. Furthermore, the landscape has been divided by housing development and roads, making it very difficult for the rabbit populations to mix.

For more info:
http://www.seacoastonline.com/articles/20081105-LIFE-811050355
http://www.mass.gov/dfwele/dfw/dfwcotontail.htm