Plain-bellied water snakes are prey items for many kinds of birds, mammals, turtles, snakes, and fish. They are predators that feed on frogs and toads, insects, and fish, thus helping to keep prey populations in balance. They undoubtedly act as hosts to various internal and external parasites.
Snakes in the genus Nerodia will flatten themselves or flee when detected. If cornered, they will strike fiercely. When attacked they will discharge an odorous musk in self defense. They are preyed on by a large number of medium to large aquatic, terrestrial, and avian predators.
Known Predators:
Anti-predator Adaptations: cryptic
Plain-bellied water snakes are large, typically solid-colored water snakes. Dorsal coloration varies among black, gray, olive-gray, brown, and pink. Some specimens show faint crossbars and lighter colored snakes can exhibit dark dorsal blotches. Plain-bellied water snakes can be distinguished from other species by the near-uniform coloration of the dorsum and both the ventral and subcaudal scales (except in some specimens of N. e. neglecta).
Nerodia e. erythrogaster is a uniform shade of brown dorsally that can be tinted with red, gray or green. The venter ranges from orange to pink. Nerodia e. flavigaster is gray to olive-gray dorsally and ventrally ranges from orange-yellow to a very pale yellow or white. Nerodia e. neglecta is dorsally black or dark brown and the venter ranges from yellowish-orange to orange-red or scarlet. The dark dorsal coloration can extend to the ventral scales, especially in the posterior region. Nerodia e. transversa ranges from gray to brown dorsally and often shows a blotchy pattern. The venter is yellow to yellow orange. Nerodia e. alta is dorsally olive-brown sometimes with dark blotches. The venter ranges from pale yellow to orange. Nerodia e. bogerti is dorsally pink to pink-brown sometimes with dark blotches. The venter varies from yellow to pink-yellow.
Juveniles of all subspecies exhibit mid-dorsal blotches alternating with lateral blotches. Dorsal coloration is lighter than that of adults. The venter is uniformally colored.
Other species of the genus Nerodia often have ventral spotting or other markings, a heavier dorsal pattern, and smaller eyes than Nerodia erythrogaster.
Average adult mass is 286 g for males and 516 g for females. Average length of adults is 76 to 122 cm. The record length to date for this species is 163.6 cm (total length). This species is sexually dimorphic, with the female growing to a larger size. Plain-bellied water snakes are ectothermic.
Average mass: Male 286; Female 516 g.
Range length: 76 to 163 cm.
Average length: 76-122 cm.
Other Physical Features: heterothermic
Sexual Dimorphism: female larger
Captive individuals of Nerodia erythrogaster have been found to live about 8 to 15 years.
Average lifespan
Status: wild: unreported years.
Range lifespan
Status: captivity: 8 to 15 years.
Average lifespan
Status: wild: unknown years.
Plain-bellied water snakes are semi-aquatic snakes, using both terrestrial and freshwater aquatic habitats. Most subspecies are found in warm temperate regions, but the range of Mexican subspecies extends into tropical climates. Terrestrial habitats used include forests, grasslands, and scrublands. Terrestrial habitats are used as travel corridors, aestivation sites, hibernation sites and occasional feeding sites. Aquatic habitats include ephemeral ponds or temporary pools, permanent lakes and ponds, swamps, bogs, marshes, small rivers, and riverine sloughs. Hibernation primarily occurs in crayfish burrows near wetlands. Feeding primarily occurs in or near ephemeral wetlands, where frogs and toads are abundant. Subspecies of Nerodia erythrogaster do not vary significantly in habitat preferences. Plain-bellied water snakes travel farther from water and use a greater variety of cover types than most other water snakes. Individuals have been found several hundred meters from the nearest water source. Upland corridors are critical travel areas. Use of these corridors has brought this species into agricultural and suburban areas where mortality can be high. Loss of wetlands and terrestrial corridors has put many populations under severe stress.
Average depth: Often hibernates just above water table m.
Habitat Regions: temperate ; tropical ; terrestrial ; freshwater
Terrestrial Biomes: savanna or grassland ; forest
Aquatic Biomes: lakes and ponds; rivers and streams; temporary pools
Wetlands: marsh ; swamp ; bog
Other Habitat Features: suburban ; agricultural ; riparian
Nerodia erythrogaster is divided into a number of subspecies. Nerodia erythrogaster erythrogaster, found from southeastern Virginia through western North Carolina, South Carolina, Georgia, with the exception of the northwest corner, northern Florida and southeastern Alabama with disjunct populations in Maryland and Delaware. Nerodia erythrogaster flavigaster is found in Alabama, northwestern Florida, Mississippi, Louisiana, eastern Texas, southeastern Oklahoma, Arkansas and areas surrounding the junction between the borders of Kentucky, Illinois and Missouri. Nerodia erythrogaster transversa is found in western Missouri through Kansas (except northwestern Oklahoma), Texas, southwestern New Mexico and a disjunct population in northeastern Mexico. Nerodia erythrogaster neglecta is found in southwestern Indiana and the border areas of adjacent states, with disjunct populations in southern Michigan, Indiana, Iowa, and western Ohio. Nerodia erythrogaster bogerti is found in Durango, Mexico. Nerodia erythrogaster alta is found in Zacatecas, Mexico. Nerodia erythrogaster is Nearctic in distribution.
Biogeographic Regions: nearctic (Native )
Plain-bellied water snakes are carnivores that feed extensively on ectotherms. Northern populations are more specialized predators on frogs and toads, whereas southern populations are sometimes more piscivorous. Crustaceans and carrion make up a small part of the diet. Confirmed prey includes species in the following families: Catostomidae, Centrarchidae, Cyprinidae, Esocidae, Fundulidae, Ictaluridae, Percidae, Poeciliidae, Ambystomatidae, Amphiumidae, Sirenidae, Bufonidae, Hylidae, Ranidae. These snakes travel long distances to reach prey in ephemeral wetlands. They will pursue prey if escape is attempted.
Animal Foods: amphibians; fish; carrion ; aquatic crustaceans
Primary Diet: carnivore (Eats terrestrial vertebrates, Piscivore )
Plain-bellied water snakes are important members of the ecosystems they inhabit. Since northern populations (particularly N. e. neglecta) are in decline and listed as threatened or endangered, research activities and wildlife viewing are in high demand.
Positive Impacts: ecotourism ; research and education; controls pest population
There are no adverse effects of plain-bellied water snakes on humans. In areas where they are threatened, certain individuals, such as land developers, may see Nerodia erythrogaster as an economic liability due to their protected status. Special permits and assessments may be necessary in some areas. If handled, these snakes will bite, but are no danger to people who leave them alone.
Plain-bellied water snakes are viviparous, fertilization is internal, and sex is determined genetically. One study found a significant relationship between amount of food consumption and growth rate from birth to seven months of age.
Nerodia erythrogaster neglecta is listed as threatened by the U.S. Fish and Wildlife Service and endangered in the states of Michigan, Ohio, and Indiana.
US Federal List: threatened
CITES: no special status
State of Michigan List: endangered
IUCN Red List of Threatened Species: least concern
Specific communication systems in Nerodia erythrogaster have not been thoroughly researched. In general, snakes use chemical communication (via the vomeronasal organ) at a distance and tactile signals for close range communications. Skin pheromones produced from the dorsal surface of females have been proven important in reproduction. Cloacal pheremones are used in defense and trailing. This is most likely the source of the odorous musk used when this species is attacked. Most snakes use tactile signaling in courtship. Vitt and Caldwell (2009) identified three phases of courtship that seem to fit the behavior of Nerodia erythrogaster. These are tactile chase, tactile alignment and intromission coitus. Chemical cues may be used when males are identifying each other in order to establish dominance. Snakes are capable of sensing vibrations and airborne acoustical signals (hearing).
Communication Channels: tactile ; chemical
Other Communication Modes: pheromones ; scent marks ; vibrations
Perception Channels: visual ; tactile ; acoustic ; vibrations ; chemical
An area for further research is to determine the effectiveness of wildlife underpasses. This could be a solution to one of the major causes of mortality, which is road crossings. When mitigation is required, the focus should be on construction of ephemeral wetlands as opposed to the traditional large deep water wetlands. Land acquisitions to protect this species should be large in size, preferably several hundred acres, and should contain a diversity of wetland types and travel corridors. Wetlands should be < 200 m apart and should be surrounded by a buffer area.
In the United States, mating reportedly takes place from April through early June and usually occurs once per year for females, though they may be able to store viable sperm for almost two years. Courtship often takes place in "cords," or groups. Cords typically include one adult female and several males (4 to 7 in one study), though it is unclear if more than one male is normally able to successfully fertilize the female. Courtship involves much tongue flicking and following of the female by males. Males then align with a female to match positions of the head and tail. The snakes then often coil around each other with tails entwined. Mating cords were observed in flooded forest wetlands with less than 15 cm of standing water. Another instance of mating took place in a pond near the shoreline. Woody debris was observed near the breeding site.
Mating System: polyandrous
After mating, the gestation period in this viviparous species is typically 3 to 4 months. Copulation occurs between May and June and births occur from August through October. The average number of offspring produced is 17.8 and can range from 2 to 55. Litter size is often significantly smaller in Mexican (tropical) subspecies. Mass at birth ranges from 3.5 g to 10.9 g with an mean mass of 6.4 g. Neonates measure 18 to 30 cm in total length. Males and females reach sexual maturity at between 3 to 4 years of age.
Breeding interval: Nerodia erythrogaster females probably breed once yearly.
Breeding season: Copulation occurs in May and June; Births occur from August through October
Range number of offspring: 2 to 55.
Average number of offspring: 17.7.
Range gestation period: 4 to 7 months.
Range age at sexual or reproductive maturity (female): 3 to 4 years.
Range age at sexual or reproductive maturity (male): 3 to 4 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; viviparous
There is no post-parturition parental care. However, females supply embryonic nutrients in the form of yolk and perhaps directly through the bloodstream (established for some natricine snakes). Viviparity is an evolutionary method of protecting offspring which involves provisioning and sacrifice. During gestation the female may be less capable of feeding and maintaining full mobility and therefore may be more susceptible to predators.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
Nerodia erythrogaster, also known as the plain-bellied water snake or plainbelly water snake, is a common species of semi-aquatic, non-venomous colubrid snake endemic to the United States.
The plain-bellied water snake is a large, thick-bodied, mostly patternless snake, with a generally beige underside. Some snakes display a thin, white line between the pale belly and their darker top scales. Subspecies can range from dark brown, gray, and olive-green to greenish-gray or blackish in color. Some lighter-colored individuals have dark dorsal patterns.[2] Plain-bellied water snakes can be distinguished from other water snakes by their “plain”, patternless undersides, which vary in color from light reddish hues to beige; this is where they get the common name “plain-bellied”, as they typically have no notable markings on their bellies.
The scientific name erythrogaster comes from the Greek word “erythros” (meaning ‘red’) and “gaster” (meaning ‘belly’).[3] This species exhibits geographically-distinct, phenotypic variations which result in a number of unique subspecies.[4] Adults vary in size from 24 to 40 inches (76–122 cm) in total length.[5] Juvenile snakes feature patterns similar to banded water snakes, but can be identified by their unmarked bellies.[6]
Plain-bellied water snakes are found in every southeastern state of the U.S., except for the higher elevations in the Appalachian Mountains (thus excluding them from eastern Tennessee and western North Carolina). On the east coast, they are found across Florida, north to southeastern Virginia, as well as western Tennessee. They are found at lower elevations from Georgia and west across the Gulf States, extending as far west as Oklahoma and Texas. The snakes are almost always found near a permanent freshwater source, usually several feet deep, and not necessarily clear or fast-moving waters, either. They can often be observed resting on branches or foliage directly over the water, for an easy escape route. In their natural geographic range, the snakes are adapted to a wetland lifestyle, often found at or near creeks, rivers, swamps, floodplains, lakes, and ponds, as well as man-made reservoirs, dams, and canals.[6]
Plain-bellied water snakes are active in the warmest months of the year. During the hottest months of summer, they will be active both during the day and at night. In warmer months, they are typically found basking on logs or near bodies of water, swimming, or traveling over land. During hot, humid weather, they will travel long distances away from water.[5] Nerodia erythrogaster is found no further than (approximately) 318 feet (97 m) away from a freshwater source, but do travel over dry land, around 98-108 feet (30-33 m) in a single day. [7]They tend to spend more time in terrestrial habitats than other water snake species. They hibernate during the coldest months of the winter.[6]
The species finds the bulk of its prey in the water. They feed primarily on tadpoles, small amphibians, fish, crayfish and other crustaceans,[8] aquatic insects (like water beetles), hatchling turtles and carrion.[9] Because of the amount of time they spend on land, the snake's diet includes a large quantity of amphibians, mostly toads and frogs. Like most other snakes, it will actively hunt for prey, but this species has also been observed submerged underwater and lying in wait for prey to approach. They apprehend and swallow prey alive without the prior use of constriction or envenomation.[6][5]
This species bears live young (ovoviviparous) like other North American water snakes and garter snakes. The snake breeds from April until mid-June in the southeast U.S. The female gives birth during the months from August to September. Large broods have been observed, but a typical litter size is around eighteen. One female was observed with a litter of fifty five hatchlings in North Carolina.[6] In 2014 a captive female produced two healthy offspring via parthenogenesis.[10]
The plain-bellied water snake is prey to both terrestrial and aquatic predators. Reported predators include largemouth bass, kingsnakes, cotton mouths, and several species of egrets, and hawks. Their usual reaction to threats of being captured are: attempts to escape, biting and releasing a foul odor. Unlike the common water snake, the plain-bellied water snake will leave water and try to escape over land if threatened.[6]
These six subspecies of N. erythrogaster have been historically recognized, including the nominotypical subspecies. However, in 2010, Makowsky, et al. determined that there was "little support for the recognized subspecies as either independent evolutionary lineages or geographically circumscribed units and conclude that although some genetic and niche differentiation has occurred, most populations assigned to N. erythrogaster appear to represent a single, widespread species."[11][12]
The plain-bellied water snake is considered a conservation risk because of loss of wetlands and other anthropogenic factors. 35% of wetlands worldwide have been lost from 1970 to 2015.[13] This species is often struck by vehicles while it crosses highways traveling from one water source to another. They are commonly mistaken for cottonmouths and are consequently killed by people averse to snakes. It is not a protected species in the southeastern states. In 1997, the subspecies, copper-bellied water snake was designated a threatened species in Ohio, Michigan and northern Indiana under the Federal Endangered Species Act.[6]
Nerodia erythrogaster, also known as the plain-bellied water snake or plainbelly water snake, is a common species of semi-aquatic, non-venomous colubrid snake endemic to the United States.
