The eastern cottontail rabbit is a long-eared, medium-sized rabbit of 36 to 48 cm in length, and weighs from 0.80 to 2 kg. Its hind legs, of about 10 cm long, are twice the length of the forelegs. It is grizzled brown on top and white underneath. Grizzled means that the tips of each hair are white or silver. This gives the fur a frosty look. Its fluffy tail is very white. It holds its tail up like a white flag as it runs. It stays almost the same color all year.

Cottontails prefer open country, such as areas with low brush, fence rows, fields of tall grass, tangled thickets, and piled brush. They often build their nests near streams although they do not go into the water willingly. European rabbits live in hills with many tunnels. This is called a 'warren'. Cottontails do not live in warrens. Each rabbit digs out a depression or hole in the ground big enough to hide itself well. This simple nest is called a 'form'. They dig the form to hide and shelter themselves and their young bunnies.

Cottontails mate as early as mid-February. In the northern limits of their range, they begin mating in March. The first litter of four to seven bunnies is born 26 to 28 days later. The form for the young is about 13 cm deep, 18 cm long, and 13 cm wide. The mother lines the 'form' with dried, soft plants. Over this, the mother puts a layer of soft fur plucked from her white underside. The bunnies weigh 28 gm, are hairless, and have closed ears and eyes. The mother rabbit nurses the bunnies with her milk at least once a day at dawn or dusk. To protect the bunnies from becoming cold, dry, or wet, the mother covers them with fur and loose soft plants after each feeding. That is the extent of her care for them when she is not in the form.

After a week, the bunnies have fur, and their eyes and ears are open. After only two weeks, the bunnies take their first hops away from the nest or form. Two days later, they leave the nest to take care of themselves.

Female cottontail rabbits can have seven litters of bunnies a year. If many cottontails did not die, there could be a population explosion. Scientists calculate that one female cottontail could produce 350 000 rabbits in just five years. Luckily this does not happen in Canada. Cottontails are among the shortest-lived medium-sized mammals. During the first two weeks of life, more than two thirds die of starvation or exposure. They also die if predators find them or the mother dies. Some drown, in the nest, during rainstorms. If the cottontail lives long enough to leave the form and care for itself, it usually lives about six months. Only one in four of these rabbits then is lucky enough to live over a year. The many natural enemies of the eastern cottontail include hawks, owls, foxes, coyotes, weasels, skunks, badgers and lynx.

Some people have seen cottontails running after each other and playing during the night. This is part of their courtship ritual before mating. It actually takes the form of a running nighttime dance. It is one way that cottontails know they are with another healthy cottontail rabbit.

If chased by an enemy, a cottontail rabbit has an interesting way of trying to escape. It will make several giant leaps to gain distance. Then it runs in a zigzag pattern. The cottontail always runs away from an enemy in a path that makes a big circle back to the spot where it started running. Hunters know this. They use dogs to chase the cottontail and wait for it to return.

Eastern cottontail rabbits have a habit of thumping the ground with a hind foot. Scientists believe the thumping is a warning of danger for other rabbits, but this is unproved.