Pantherophis alleghaniensis

Eastern ratsnake
Adult eastern ratsnake Murphys Point Provincial Park, Ontario
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Subphylum:	Vertebrata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Colubridae
Subfamily:	Colubrinae
Tribe:	Lampropeltini
Genus:	Pantherophis
Species:	P. alleghaniensis
Binomial name
Pantherophis alleghaniensis (Holbrook, 1836)[1]
Synonyms
Coluber alleghaniensis Holbrook, 1836[1] Scotophis alleghaniensis — Baird & Girard, 1853[2] Elaphis alleghaniensis — Hallowell, 1856[3] Pantherophis alleghaniensis — Garman, 1892[4] Coluber obsoletus — Boulenger, 1894 (part)[5] Elaphe obsoleta — Stejneger & Barbour, 1917 (part)[6] Elaphe alleghaniensis — Burbrink, 2001[7] Scotophis alleghaniensis — Collins & Taggart, 2008[8] Pantherophis alleghaniensis — Pyron & Burbrink, 2009[9]

Pantherophis alleghaniensis, commonly called the eastern ratsnake, is a nonvenomous colubrid species endemic to North America.^[9][10]

Common names

Eastern rat snake, black rat snake, pilot snake, pilot rat snake,^[10] chicken snake; and in Florida, yellow rat snake and Everglades rat snake^[11]

Geographic range

Eastern rat snake (subadult), Pantherophis alleghaniensis, in Maryland

Pantherophis alleghaniensis is found in Canada, particularly southern Ontario, and in the United States east of the Apalachicola River in Florida, east of the Chattahoochee River in Georgia, east of the Appalachian Mountains, north to southeastern New York and western Vermont, eastern Pennsylvania, Maryland, South Carolina, North Carolina, Georgia, south to the Florida Keys.^{[9][10][11][12]} In the Florida Panhandle, it readily hybridizes with the gray rat snake (Pantherophis spiloides).^[11]

Description

Yellow rat snake, Pantherophis alleghaniensis ssp. quadrivittata, in Florida

Adult snakes commonly measure 91.4 to 183 cm (36.0 to 72.0 in) in total length (including tail), with a few exceeding 200 cm (79 in).^[11] The longest recorded total length to date is 256.5 cm (101.0 in).^[10]

Adults are shiny black dorsally, with a cream or white chin and throat. The belly has an irregular black and white checkerboard pattern, becoming uniformly slate gray towards the tail. Juveniles have dark dorsal blotches on a grayish ground color. The ventral pattern in juveniles is the same as in adults. The eyes are round with a black pupil, and particularly in juveniles but not always present in adults, a distinct white margin.^[10][12]

The dorsal scales are weakly keeled, and are arranged in 23 to 27 rows at midbody.^[13]

Males and females have the same coloration. Males have proportionally longer tails (16-19% of total body length) compared to females (14-18% of total body length).^[10]

Habitat

The eastern rat snake occurs in a variety of habitats. These include farmlands, hardwood forests, forested wetlands, thickets and fields adjacent to forests, isolated urban woodlots and backyards that support populations of prey species. Eastern rat snakes do especially well in early successional and edge habitats. An arboreal species, the snakes get into human residences, where they may live in attics undetected. At the northern limits of their range, distribution appears to be restricted by the availability of suitable hibernating sites. In these climes, the snakes require southern exposures to receive maximal thermal benefit from the winter sun and to provide basking areas in early spring and late fall.^[10][12]

Behavior and Ecology

The eastern rat snake is primarily active at night during the summer, and diurnal in the spring and fall.^[14] It is a terrestrial burrower and an excellent climber, and it may enter water. It is found under rocks and boards, and in trees under bark and within knot holes and palm fronds. The snake is a constrictor, and adults eat mainly endotherms while young eat mainly ectotherms. The diet includes rodents, lizards, frogs, and birds and their eggs.^[15] The snakes can also eat young chickens and chicks, hence the common name chicken snake.

Rat snakes are most vulnerable to predators as juveniles. Predators of P. alleghaniensis include hawks (Buteo spp.), great horned owls (Bubo virginianus), foxes, raccoons, and domestic cats. Adult eastern rat snakes have few known predators other than humans. When frightened, a rat snake will freeze. If harassed, it will produce a foul-smelling musk to deter predators. If provoked further, it may coil, shake its tail, and snap at its attacker.^[16]

The snakes hibernate during the winter underground or in deep crevices. They may congregate in the same dens with other species of snakes, such as copperheads (Agkistrodon contortrix), black racers (Coluber constrictor), and timber rattlesnakes (Crotalus horridus). In Northern climes, the snakes are active from late April to October and mate in May or June. It is active earlier in the South.^[17]

Rat snakes reach sexual maturity in their fourth year. The snakes start to breed in May and June, earlier in the South. Males approach females to initiate breeding and may combat other males before breeding. About five weeks after mating, the female lays 5 to 27 eggs in hollow standing and fallen trees, compost and mulch heaps, sawdust piles, and decomposing logs. Incubation is about two months, and eggs hatch from July through September. Hatchlings are usually just over a foot long at birth, with the distinct gray and black pattern characteristic of juveniles.^[14][16][17]

Taxonomy

Pantherophis alleghaniensis has sometimes been considered a subspecies of Pantherophis obsoletus, to which it is closely related.^[18]

This opportunistic yellow rat snake is looking for his next meal high atop this Live Oak tree. Just before he arrives at a bird's nest to eat the eggs that are in it, an angry mama Blue Jay frantically swoops down several times at him, causing him to change his mind and look for his breakfast elsewhere.

This species has often been placed in the genus Elaphe, but recent phylogenetic analyses have resulted in its transfer to Pantherophis.^[19][20][21]

References

Further reading

• Holbrook JE. (1836). North American Herpetology; or, A Description of the Reptiles Inhabiting the United States. Vol. I. Philadelphia: J. Dobson. 120 pp. (Coluber alleghaniensis, pp. 111-112 + Plate XX).
• Jan G, Sordelli F. (1867). Iconographie générale des Ophidiens: Vingt-quatrième livraison. Paris: Baillière. Index + Plates I-VI. (Elaphis alleghaniensis, Plate II, Figure 1 [adult], Figure 2 [juvenile]).

External links

Wikimedia Commons has media related to Pantherophis alleghaniensis.

• Pantherophis alleghaniensis at the Reptarium.cz Reptile Database. Accessed 29 November 2008.