Eastern rat snake

Identification

Adults are large, stout snakes that are glossy black above, with a white chin and throat and an irregular black-and-white checkerboard belly that fades towards the tail^4,5. Some keep faint stripes or traces of the young snake’s blotches⁴. The scales along the middle of the back are weakly keeled, and the body is flat-bottomed, shaped like a loaf of bread in cross-section^4,6.

Young rat snakes are grey with 28–40 dark blotches and a dark stripe from the eye to the corner of the mouth; this pattern usually fades to black by about 60 cm long, although the snake may take four to five years to become fully black^4,7. Adults usually measure 1.07–1.83 m, and the largest known specimen measured 2.56 m⁴. It is Ontario’s largest snake, reaching about 2 m there⁵.

Distribution

This species lives in the eastern United States, from the Mississippi River east to the Atlantic Seaboard Fall Line in Virginia, and north to Wisconsin, Michigan, New York, Vermont and Massachusetts³. It also reaches southern Ontario in Canada¹, where there are two widely separated populations, one in the south-west and one in the south-east of the province⁵.

These snakes were long treated as one species, the black rat snake, before genetic studies split them into western, central and eastern species³. In 2021 the original specimen of P. alleghaniensis, from the Blue Ridge in Virginia, was shown to belong to the central group, so the name now covers the central snakes once called the grey rat snake (P. spiloides); the coastal-plain and Florida snakes are the yellow rat snake (P. quadrivittatus), and those west of the Mississippi are P. obsoletus^1,2,3. The 2025 standard list of North American names calls this species the central ratsnake, but many guides and agencies still call it the eastern or black rat snake^2,3,6.

Habitat

Rat snakes do best where woodland is mixed with open ground, such as fields, thickets, wetland edges and rocky outcrops³. In Connecticut they live in rough, forested terrain with ledges and rock outcrops, and in small meadows next to woodland⁶. They are often found in farmland, hardwood forest and around barns and old buildings, where rodents are common⁴. They shelter in hollow trees, logs, rock crevices and under rocks³.

In the north they need good winter dens, often in rocky talus or ledges facing south, and they return to the same den year after year^3,6. Dens are often shared with other snakes, including racers, copperheads and timber rattlesnakes^3,6.

Behaviour

Rat snakes are active by day and at night, and are often out just after sunset^4,6. They are excellent climbers that often go high into trees, attics and haylofts, and they also swim well^3,5,6.

When it meets a person, a rat snake often keeps still, and if alarmed it may vibrate its tail in dry leaves, which can sound like a rattlesnake⁶. A cornered snake may raise its front body in an S-shaped coil, hiss and strike⁴. If grabbed, it may bite repeatedly, wrap around the arm and release a foul-smelling musk⁶.

Diet

Rodents, birds and birds’ eggs are the main prey⁴. Recorded mammal prey includes chipmunks, grey squirrels, cottontail rabbits, voles and mice, and many of the birds taken are nestlings⁴. Rat snakes also eat lizards, frogs and insects^4,6. Prey is killed by constriction, while eggs are swallowed whole and broken in the throat⁴.

Reproduction

Rat snakes lay eggs. Mating takes place in late spring, soon after the snakes leave their winter dens, and males may fight over females^3,5. A clutch holds 5–44 eggs, about 14 on average, laid in rotting logs, leaf litter, compost or sawdust piles³. The eggs hatch after 60–75 days, usually by late summer³. Several females may use the same nest site, and young from these shared nests tend to be fitter than those from solitary nests³.

Growth is slow in the north: rat snakes in Maryland mature at about 4 years old, but those in Ontario take 10–12 years³.

Venom and medical significance

The eastern rat snake has no venom and is harmless to people^5,6. Like most snakes, it will bite if grabbed or cornered, and a handled snake may also smear a foul-smelling musk^4,6.

The belief that rat snakes and copperheads interbreed to produce venomous young is a myth, because the two are only distantly related⁴.

Conservation

The IUCN Red List assessed North American rat snakes in 2019 under the older names. Its assessment of Pantherophis spiloides covers the snakes now called P. alleghaniensis, and it and the assessment published under the name P. alleghaniensis both list them as Least Concern^3,9,10.

The species is still common in much of its range, but northern populations are declining³. It is listed as Endangered in Massachusetts and Threatened in Vermont³. In Canada, the Carolinian population is listed as Endangered and the Great Lakes/St. Lawrence population as Threatened^3,5. The main threats are habitat loss, especially of winter dens, road deaths and persecution by people^3,5.

Similar species

The northern black racer (Coluber constrictor) is the snake most often confused with an adult rat snake⁴. Racers have smooth scales, a rounded body and dark eyes, and only the chin is white; rat snakes have weakly keeled scales, a checkered belly and a clearly visible iris^4,6.

Young rat snakes are sometimes mistaken for young copperheads (Agkistrodon contortrix), which are venomous and have brown hourglass-shaped crossbands and a yellowish tail tip⁴. They can also look like young corn snakes (Pantherophis guttatus), but corn snakes have a spear-shaped mark between the eyes that young grey rat snakes lack⁸.

These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

Rat snakes are popular in the pet trade, and collecting them from the wild has harmed some populations⁶. Connecticut’s wildlife agency advises never taking a wild snake as a pet, because wild-caught snakes often suffer from infection, parasites and stress in captivity⁶. Snakes of this complex, then all called Elaphe obsoleta, have lived up to 33.9 years in captivity¹¹. A pet snake should never be released, because it may carry diseases into wild populations⁶.