The common watersnake (Nerodia sipedon)[4] is a species of large, nonvenomous, common snake in the family Colubridae. The species is native to North America. It is frequently mistaken for the venomouscottonmouth (Agkistrodon piscivorus).
Common names for N. sipedon include banded water snake, black water adder, black water snake, brown water snake, common water snake, common northern water snake, eastern water snake, North American water snake, northern banded water snake, northern water snake, spotted water snake, streaked snake, water pilot, and water snake.[5]
Description
The common watersnake can grow up to 135cm (4ft 5in) in total length (including tail).[6] Per one study, the average total length of females was 81.4cm (2ft 8in), while that of males was 69.6cm (2ft 3+1⁄2in).[7] From known studies of this species in the wild, adult females can weigh between 159 and 408g (5+1⁄2 and 14+1⁄2oz) typically, while the smaller male can range from 80.8 to 151g (2+7⁄8 to 5+3⁄8oz).[8][9][10][11] The largest females can weigh up to 560g (20oz) while the largest males can scale 370g (13oz).[12][13]
N. sipedon can be brown, gray, reddish, or brownish-black. It has dark crossbands on the neck and dark blotches on the rest of the body, often leading to misidentification as a cottonmouth or copperhead by novices. As N. sipedon ages, the color darkens, and the pattern becomes obscure. Some individuals become almost completely black. The belly also varies in color. It can be white, yellow, or gray; usually, it also has reddish or black crescents.
The common watersnake is nonvenomous and harmless to humans, but superficially resembles the venomous cottonmouth. It is often killed by humans out of fear; killing snakes greatly increases the chance of being bitten.[14] The two can be easily distinguished: the watersnake has a longer, more slender body and a flattened head the same width as the neck, round pupils, and no heat-sensing pits. The cottonmouth has a fatter body, a wedge-shaped head with prominent venom glands that are wider than the neck, cat-like pupils, and heat-sensing pits between the eyes and the nostrils.[14]
Colubrid snakes also have flat scales on their heads, while vipers all possess smaller, rugose scutes.
Subspecies
These four subspecies are recognized as being valid:[2]
The common watersnake is found throughout eastern and central North America, from southern Ontario and southern Quebec in the north, to Texas and Florida in the south. The Northern Watersnake (Nerodia s. sipedon) naturally occurs as far west as Colorado, east of the Rocky Mountains, commonly found in riparian ecosystems along several river systems, including the South Platte River and Arkansas River to name a few. [15] In 2007 an introduced population was discovered in California, where the related species N. fasciata has been introduced since at least 1992.[16][17]
Introduction
While native to the eastern US, water snakes in California are considered invasive species likely to compete with native giant garter snakeThamnophis gigas, a threatened species.[17][18][19][20] Garter snakes in the western U.S. have filled the aquatic snake niche in the absence of true water snakes.[21] The common watersnake may threaten vulnerable fish and amphibian species via excess predation.[21] Common watersnakes are thought to have been introduced to western states as pets that were released.[21] In 2008 it was made illegal in California to own or import common watersnakes without a permit.[21]
Behavior
Northern watersnake basking west of Ottawa, Ontario
N. sipedon is active during the day and at night. It is most often seen basking on rocks, stumps, or brush. During the day, it hunts among plants at the water's edge, looking for small fish, tadpoles, frogs, worms, leeches, crayfish, large insects, mollusks, annelid[22] salamanders, other snakes, turtles, small birds, and mammals.[23] At night, it concentrates on minnows and other small fish resting in shallow water. It hunts using smell and sight. The Lake Erie watersnake subspecies, N. s. insularum, was once endangered, but now benefits from the introduction of the round goby, an invasive species, which constitutes up to 90% of its diet.
The common watersnake is common over most of its range and is frequently seen basking on stream banks, from which it dives into the water at the slightest disturbance. "Water snakes are highly aquatic, spending nearly all their time either on the surface of the water or on substrate just above or beside the water".[24] It is quick to flee from danger, but if cornered or captured, it usually does not hesitate to defend itself. Larger specimens can inflict a painful bite.
Reproduction
The common watersnake mates from April through June. It is ovoviviparous (live-bearing), which means it does not lay eggs like many other snakes. Instead, the mother carries the eggs inside her body and gives birth to free-living young, each one 19–23cm (7+1⁄2–9in) long.[25] A female may have as many as 30 young at a time, but the average is eight. They are born between August and October. Mothers do not care for their young. Females are known to be larger in both length and mass when compared to males.[26] Multiple mating by females is common, leading to a focus in sperm competition. Research suggests successful males are not the ones who dedicate more energy to size, but to sperm.[7] Males typically reach sexual maturity during their second year, generally around 21 months.[27] Northern water snakes can perform vitellogenesis, which is when they create extra yolk protein for the young, and since this costs a lot of energy they have to store up a lot of fat.[28]
Homeostasis
“Nerodia sipedon are effective thermoregulators”.[29]
Defense against predators
N. sipedon has many predators, including birds, raccoons, opossums, foxes, snapping turtles, other snakes, and humans. The common watersnake defends itself vigorously when threatened. If picked up by an animal or person, it will bite repeatedly, and release excrement and musk. Its saliva contains a mild anticoagulant, which can cause the bite to bleed more, but poses little risk to humans.
Habitats
N. sipedon inhabits streams, lakes, and ponds, as well as wetlands. Juveniles typically inhabit lower-order streams adjacent to the larger-order waterways where adults are found. This helps juveniles to avoid predators such as fish, birds, and turtles present in large water bodies.[30] They tend to select areas further away from the bank out in the open in dead cattail clumps or low hanging branches. [31]
Conservation status
The Lake Erie watersnake, which occurs mainly on the lake's western islands offshore from Ohio and Ontario, recovered to the point where on August 16, 2011, the U.S. Fish and Wildlife Service removed it from the Federal List of Endangered and Threatened Wildlife. The subspecies was first listed as threatened in 1999 after a decline due to eradication by humans, as well as habitat loss and degradation. When initially listed, the subspecies’ population had dropped to only 1,500 adults. Endangered Species Act protections for the snake included designation of 120ha (300 acres) of inland habitat and 18km (11mi) of shoreline for breeding grounds. Wetlands have been lost at an astounding rate over the years, and the reptiles within those wetlands have shown a decline as well.[32] The introduction of an invasive species, the Eurasian round goby (Neogobius melanostomus) into Lake Erie in the mid-1990s became a new food source for the Lake Erie watersnake. By 2009, the population recovered to 11,980 snakes, safely exceeding the population minimum goal of 5,555 adult snakes required by the 2003 recovery plan. Monitoring was to occur for 5 years following this delisting. The Lake Erie watersnake is just the 23rd species or subspecies to be removed from the list due to recovery.[33]
Agkistrodon piscivorus is a species of venomous snake, a pit viper in the subfamily Crotalinae of the family Viperidae. It is one of the world's few semiaquatic vipers, and is native to the Southeastern United States. As an adult, it is large and capable of delivering a painful and potentially fatal bite. When threatened, it may respond by coiling its body and displaying its fangs. Individuals may bite when feeling threatened or being handled in any way. It tends to be found in or near water, particularly in slow-moving and shallow lakes, streams, and marshes. It is a capable swimmer, and like several species of snakes, is known to occasionally enter bays and estuaries and swim between barrier islands and the mainland.
Nerodia is a genus of nonvenomous colubrid snakes commonly referred to as water snakes due to their aquatic behavior. The genus includes nine species, all native to North America. Five of the species have recognized subspecies.
Nerodia rhombifer, commonly known as the diamondback water snake, is a species of nonvenomous natricine colubrid endemic to the central United States and northern Mexico. There are three recognized subspecies of N. rhombifer, including the nominotypical subspecies.
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 Florida cottonmouth is a species of venomous snake, a pit viper in the subfamily Crotalinae of the family Viperidae. The species is endemic to the United States, where it occurs in southern Georgia and the Florida peninsula in nearly every type of wetlands in the region, including brackish water and offshore islands. However, it is not entirely dependent on water and is occasionally encountered as far as a mile from surface water. Agkistrodon conanti venom is very hemolytic and known to cause relatively extensive necrosis compared to many snake venoms, and can sometimes be lethal with a 17% mortality rate. It is often confused with harmless watersnakes (Nerodia) and other semi-aquatic species with which it shares its habitat.
Nerodia paucimaculata, commonly known as the Concho water snake, is a species of mostly aquatic, nonvenomous snake in the family Colubridae. The species is endemic to Texas in the United States.
The Brazos water snake, also called commonly Harter's water snake, is a species of mostly aquatic, nonvenomous snake in the family Colubridae. The species is endemic to Texas in the United States.
The banded water snake or southern water snake is a species of mostly aquatic, nonvenomous, colubrid snakes most commonly found in the Midwest, Southeastern United States.
Nerodia clarkii, commonly known as the salt marsh snake, is a species of semi-aquatic, nonvenomous, colubrid snake found in the southeastern United States. Their range extends along the brackish salt marshes of the Gulf of Mexico and the Atlantic Coast from Texas to Florida, with an additional population in northern Cuba. Different subspecies of this snake are primarily identified via color patterns on each snake's belly, or anterior.
Regina grahamii, commonly known as Graham's crayfish snake, is a species of nonvenomous semiaquatic snake in the subfamily Natricinae of the family Colubridae. The species is endemic to the central United States.
The crayfish snake, also known commonly as the glossy crayfish snake, the glossy swampsnake, the glossy water snake, and the striped water snake, is a species of semiaquatic snake in the subfamily Natricinae of the family Colubridae. The species is endemic to the southeastern United States, and preys mainly on crayfish.
The Florida banded water snake, a subspecies of the banded water snake, is a nonvenomous natricine colubrid native to the southeastern United States.
The green water snake is a common species of nonvenomous natricine snake endemic to the southeastern United States.
The brown water snake is a large species of nonvenomous natricine snake endemic to the southeastern United States. This snake is often one of the most abundant species of snakes found in rivers and streams of the southeastern United States, yet many aspects of its natural history is poorly known. Due to abundance and distribution throughout its biological range, this species could be used to investigate anthropogenic impacts on aquatic ecosystems by studying their movements.
The midland water snake, a subspecies of the northern water snake, is a nonvenomous natricine snake, which is endemic to North America.
Nerodia floridana, commonly known as the Florida green watersnake, or eastern green watersnake, is a harmless species of snake in the subfamily Natricinae of the family Colubridae. The species is native to the southeastern United States.
The Lake Erie watersnake, a subspecies of the common watersnake, is a nonvenomous natricine snake. It is found on the offshore islands of Western Lake Erie, as well as the mainland of Ottawa County, Ohio. In 1999 the U.S. Fish and Wildlife Service listed the subspecies as a threatened subspecies after the population fell to 1,500 individuals. In 2011, the subspecies was removed from the list after the population increased to nearly 12,000 individuals by 2009.
↑ Stejneger L, Barbour T (1917). A Check List of North American Amphibians and Reptiles. Cambridge, Massachusetts: Harvard University Press. 125 pp. (Natrix sipedon, p. 96).
1 2 Weatherhead, Patrick J.; Barry, Frances E.; Brown, Gregory P.; Forbes, Mark R. L. (1995). "Sex ratios, mating behavior and sexual size dimorphism of the common water snake, Nerodia sipedon ". Behavioral Ecology and Sociobiology. 36 (5): 301–311. doi:10.1007/BF00167791. S2CID22311826.
↑ Jellen, Benjamin C.; Aldridge, Robert D. (2014). "It takes two to tango: Female movement facilitates male mate location in wild common watersnakes (Nerodia sipedon)". Behaviour. 151 (4): 421–434. doi:10.1163/1568539X-00003128.
↑ Brown, Gregory P.; Weatherhead, Patrick J. (2000). "Thermal Ecology and Sexual Size Dimorphism in Northern Water Snakes, Nerodia sipedon ". Ecological Monographs. 70 (2): 311–330. doi:10.1890/0012-9615(2000)070[0311:TEASSD]2.0.CO;2.
↑ Schulte-Hostedde, A.I.; Montgomerie, R. (2006). "Intraspecific variation in ejaculate traits of the northern watersnake (Nerodia sipedon)". Journal of Zoology. 270 (1): 147–152. doi:10.1111/j.1469-7998.2006.00101.x.
↑ Brown, Gregory P.; Weatherhead, Patrick J. (1999). "Demography and sexual size dimorphism in northern watersnakes, Nerodia sipedon ". Canadian Journal of Zoology. 77 (9): 1358–1366. doi:10.1139/z99-112.
↑ Weatherhead, Patrick J.; Brown, Gregory P. (1996). "Measurement versus estimation of condition in snakes". Canadian Journal of Zoology. 74 (9): 1617–1621. doi:10.1139/z96-179.
↑ King RB (2002). "Predicted and observed maximum prey size – snake size allometry". Functional Ecology. 16 (6): 766–772. doi:10.1046/j.1365-2435.2002.00678.x.
↑ Schmidt KP, Davis DD (1941). Field Book of Snakes of the United States and Canada. New York: G.P. Putnam's Sons. 365 pp. (Natrix sipedon, pp. 219-222, Figure 22 (map) + Plate 24 on p. 344).
↑ Brown, G. P., & Weatherhead, P. J. (1999). Female Distribution Affects Mate Searching and Sexual Selection in Male Northern Water Snakes (Nerodia sipedon). Behavioral Ecology and Sociobiology, 47(1/2), 9–16. https://doi.org/10.1007/s002650050644
↑ Conant R (1975). A Field Guide to Reptiles and Amphibians of Eastern and Central North America, Second Edition. Boston: Houghton Mifflin. xviii + 429 pp. ISBN0-395-19979-4 (hardcover), ISBN0-395-19977-8 (paperback). (Natrix sipedon, pp. 144-146 + Plate 20 + Map 99).
↑ Bishop, C. A., & Rouse, J. D. (2000). Chlorinated Hydrocarbon Concentrations in Plasma of the Lake Erie Water Snake (Nerodia sipedon insularum) and Northern Water Snake (Nerodia sipedon sipedon) from the Great Lakes Basin in 1998. Archives of Environmental Contamination and Toxicology, 39(4), 500–505. https://doi.org/10.1007/s002440010133
↑ Rowe, J. W., Goerge, T. M., Martin, C. E., & Mulligan, W. P. (2022). Thermal ecology of Northern Water Snakes (Nerodia sipedon) in a northern wetland in central Michigan. Journal of Thermal Biology, 105, 103204–103204. https://doi.org/10.1016/j.jtherbio.2022.103204
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Holbrook JE (1842). North American Herpetology; or, A Description of the Reptiles Inhabiting the United States. Vol. IV. Philadelphia: J. Dobson. 138 pp. + Plates I-XXXV. (Tropidonotus sipedon, pp.29–31 + Plate VI).
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