|Common Name:||Plain-bellied Watersnake|
|Scientific Name:||Nerodia erythrogaster|
|Genus:||Nerodia is derived from the Greek words neros meaning "flowing" or "liquid" and dia meaning "through".|
|Species:||erythrogaster is derived from the Greek words erythros which means "red" and gaster meaning "belly".|
|Vernacular Names:||Agassiz's watersnake, copper-bellied moccasin, orange-bellied moccasin, red-bellied black snake.|
|Average Length:||30 - 48 in. (76 - 122 cm)|
|Virginia Record Length:||58 in. (147.4 cm)|
|Record length:||62 in. (157.5 cm)|
PHYSICAL DESCRIPTION: The adult is solid brown, reddish brown or dark olive above with a red or orangish-red belly. There are no blotches, spots or other markings on the adult. The juveniles has brown blotches down the back with smaller blotches on the sides and an orange-red ground color. The dorsal scales are strongly keeled with 23-25 scales rows and the anal plate divided. There are loreal and preocular scales present. This species is about 10 inches long at birth to over 5 feet in some adults. The adults are heavy bodied and usually from 30-48 inches in length *1006*. In VA., maximum known SVL is 1189 mm (46.8 in.) and maximum total length is 1474 mm (58.0 in.). Tail length/total length ratio is 17.2-27.7 (avg. = 21.9+/-2.5, n=41). Outside Virginia, the maximum known total length is 62 inches *11523*. Adults are usually 30-48 inches in length *11523*.
SCUTELLATION: ventrals 135-154 (avg. = 147.5+/-3.0, n=64); subcaudals 50-84 (avg. = 71.3+/-7.8, n=44); ventrals + subcaudals 200-232 (avg. = 218.7+/-7.5, n=44); dorsal scales keeled; scale rows 22-23 (80.4%, n=51), 21, 24, or 25 (19.6%) at midbody; anal plate divided; infralabials 10-10 (73.7%, n=57), other combinations of 9-12 (26.3%); supralabials 8-8 (97.0%, n=57, other combinations of 7-9 (3.0%); loreal scale present; preoculars 1-1; postoculars usually 3-3; temporal scales 1+3/1+3 (70.2%, n=57), other combinations of 1-3 (29.8%).
COLORATION and PATTERN: dorsal pattern uniform rich reddish brown; venter of body and tail uniform orange to red; dorsal coloration encroaches onto margins of venter in some individuals; dorsum of head dark brown; rostrum and lateral portion of snout tan to reddish brown; chin and infralabials are white to yellowish; supralabials reddish, tan, or white and may be outlined in dark drown; red color on venter fades to cream or light tan in preservative. These stout snakes are distinctly bicolored with a distinct head and large eyes. Eye diameter is equal to or greater than the distance between the eye and nostril.*10760*
SEXUAL DIMORPHISM: Adult females average larger (738-1189 mm, avg. = 958.0+/-117.9, n=29) than males (550-1100 mm, avg. = 807.0+/-141.9, n=24) in body size, and reach a larger total length (to 1474 mm) than males (to 1235 mm). Sexual dimorphism index is 1.19. Females also reach a larger body mass (to 813 g) than males (to 556 g). Tail length/total length ratio is similar between sexes (females 18.1-26.6, avg. = 21.1+/-2.4, n=20; males 17.2-27.7, avg. = 22.6+/-2.4, n=20), as is the number of ventral scales (females 145-154, avg. = 148.5+/-2.1. n=33; males 135-153, avg. = 146.3+/-3.4, n=30). the number of subcaudal scales is higher in males (50-84, avg. = 74.6+/-8.5, n=22) than in females (63-81, avg. = 67.4+/-4.6, n=21). Consequently, the number of ventrals + subcaudals is higher in males (200-232, avg. = 221.2+/-8.7, n=21) than females (208-230, avg. = 215.6+/-4.6, n=21). Males and females do not differ in color or pattern.*10760*
JUVENILES: Juveniles are strongly patterned with a series of 4-6 dark crossbands anteriorly that change to middorsal blotches with alternating dark lateral blotches at the midbody region. Number of body crossbands and blotches average 33.4 +/-2.7 (21-40, n=52). The venter of the body and tail is uniform cream to yellow. The chin and labials are usually cream in color, and the labial scales are outlined in dark brown. The rostrum and lateral portions of the snout are tan. The juvenile pattern becomes obscure with age. At birth, juveniles are 192-244 mm SVL (avg. = 218.5+/-13.4, n=74), 251-310 mm total length (avg. = 282.1+/-17.1), and weigh 5.7-9.8 g (avg. = 8.4+/-0.7, n=4).*10760*
CONFUSING SPECIES: Adults of this species may be confused with Pantherophis alleghaniensis and Coluber constrictor which are smooth scaled and have black and white or gray venters. Some darkly-colored individuals of Nerodia sipedon may be confused with N. erythrogaster, but they have a strongly patterned venter rather than a uniform reddish venter. The differences in ventral pattern and coloration as well as the larger number of anterior dorsal crossbands in N. sipedon will distinguish juveniles of the 2 species of water snakes in SE VA.*10760* No geographic variation in color, pattern, or scutellation occurs in VA.*10760.
REPRODUCTION: The females bear up to 50 live young which are between 12-15 inches in length. The young are born in the late summer or early fall *1006*. Mating occurs April through June.*10760*
BEHAVIOR: This species is the most terrestrial of the Nerodia and will wander hundreds of yards into dry forests during the summer. They usually rest directly on the ground. This species feeds on mainly frogs and fishes *1006*. The eastern kingsnake (Lampropeltis getula getula) is a known predator of the red-bellied watersnake. The red-bellied watersnake is both diurnal and nocturnal. This species will often bite or discharge musk when seized or restrained *11523,11499*. Thorp has often found this species on land or under cover boards a few feet to fifty yards away from water *11523*.
POPULATION PARAMETERS: This species will bear up to 50 young. The maximum known age is 8 years 10 months and 2 days *1006,11523*.
AQUATIC/TERRESTRIAL ASSOCIATIONS: Predators include raccoons, herons, kingsnakes, snapping turtles and large fish *1006*. Predators include snapping turtles (Chelydra serpentina), hawks, (Buteo spp.), and humans.*10760* Nothing is known of the population ecology of the red-bellied water snake anywhere in its range. Werler and McCallion noted that it was fairly common in Seashore State Park, but there may have been a substantial decline in the population since the 1970's, possibly due to the low water conditions in the 1980's.*10760*
References for Life History
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