University of Massachusetts Amherst

Massachusetts North American Amphibian Program

Eastern Ratsnake

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Herp Atlas 1992-1998 Survey

  • The map below shows the distribution of the Black Rat Snake in Massachusetts based on the original intensive volunteer survey that took place from 1992-1998.
  • Download pdf of map

Updated Distribution Map

Pantherophis alleghaniensis (42-72", up to 101")
MA Status: "Endangered." Illegal to harass, kill, collect or possess.

Black Rat Snake
Black Rat Snake
Black Rat Snake

Our largest snake, the black rat snake can reach a length of eight feet, but is usually much smaller. The adult snake is black with a white or creamy yellow chin and throat. In contrast to the black racer, the belly of a rat snake is a mixture of light and dark, giving a somewhat mottled appearance. Light areas are often apparent between scales, and the scales on the back are weakly keeled. A juvenile rat snake is gray with light spots running down the middle of the back, and has white eyes. This pattern darkens with age and is generally undetectable once the snake reaches a length of three feet.

Mating generally takes place in the spring, with 10-14 eggs laid in June or July. Eggs deposited beneath rocks or in manure piles, rotting vegetation, stumps or logs generally hatch in August and September.

Exceedingly rare in Massachusetts, black rat snakes have been found only in the Connecticut Valley and southern Worcester County, where they occupy rocky ledges and forested hillsides. Mammals, birds and bird eggs make up the bulk of their diet and rat snakes will readily climb trees to raid bird and squirrel nests. Young rat snakes feed on frogs and other small prey. Black rat snakes readily bask in the open during spring and fall. Although they are not particularly aggressive, they may bite, defecate or spray musk when handled. Tail rattling may lead some people to mistake them for rattlesnakes.



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