A distinguishing feature of southern watersnakes is a dark stripe that extends from the eye to the angle of the jaw, but other coloration is variable. The base color can be gray, tan, dark olive, or black. The belly is typically off-white or white. The dorsal cross bands, which cover the entire body length, can also vary in color. Subspecies are distinguished based on banding patterns, color patterns, and ventral scale numbers. Nerodia f. fasciata has dark ventral markings that are square-shaped and more than 128 ventral scales. Nerodia f. confluens has dark body bands that are wider than N. f. fasciata, and only 11 to 17 bands are present along the length of the body as a result. Individuals of N. f. confluens also have rectangular, reddish-brown spots on the sides of the venter. Nerodia f. pictiventris can have dark brown, black, or reddish bands, dark lateral spots between the bands, and wavy, reddish transverse lines on the belly. Neonates are more vividly colored and patterned than adults.
Adult southern watersnakes range from 61 to 106.7 cm in length, whereas neonates tend to be about 24 cm long. These snakes exhibit sexual dimorphism in which females are typically longer and heavier than males. They have a standard metabolic rate of 1.21cm3/h at 25°C. (Bartlett and Bartlett, 2005; Dorcas and Gibbons, 2004; Ernst and Ernst, 2003; Hopkins, et al., 2004; Hopkins, et al., 1999; Semlistch and Gibbons, 1982)
Young southern watersnakes are born alive. Females carry their young during the spring and early summer and give birth in the months of July, August, September, and October. While the females carry their young, the developing embryos are nourished via a placenta. The gestation period averages about 79 days, depending on the temperature. It has been suggested that the gestation period shortens at higher elevations but there is not enough research to support such an assertion. Embryos cannot tolerate temperatures beyond the 21 to 30°C range for the entire gestation period; however, the sex of the neonates is not dependent on temperature. After birth, young snakes can reach sexually maturity in about two to three years. Individuals grow throughout their lifetime but their growth rate decreases with age. (Ernst and Ernst, 2003; Kofron, 1979; Viets, et al., 1994)
A female will start ovulating from early May to mid-June after awakening from a period of hibernation. Males produce sperm in the fall that will be ready for summer mating. Individuals start mating from early April to mid-June. Males have been seen congregating in the water before a period of mating, but there is not enough field evidence to suggest that this species is indeed polyandrous. Males pursue females. Once a female is caught, the male will crawl anteriorly onto her back until the head of the female is reached. When the head is reached, the male will pin it down and then he will position his tail beneath that of the female, bringing their two vents together. Copulation generally lasts about 60 minutes. (Dorcas and Gibbons, 2004; Ernst and Ernst, 2003)
Breeding season varies with locality and subspecies. In general, the breeding period extends from early April to mid-June. Females ovulate from May to June after awakening from a period of hibernation. They undergo vitellogenesis, which includes rapid yolk deposition and follicle growth. Males produce sperm in the fall, but they mate after emerging from the hibernation period. Copulation takes at least 60 minutes. As far as gestation period is concerned, it is assumed to become shortened at higher elevations; however, there is not enough research to support such an assertion. The average gestation period is about 79 days. Larger females tend to have larger litter sizes. Females give birth as early as July and as late as October. The average litter size is about twenty, but there is no evidence suggesting that females can have two litters in one season. (Dorcas and Gibbons, 2004; Ernst and Ernst, 2003; King, et al., 2009; Kofron, 1979; Krysko and King, 2010; Lorenz, et al., 2011)
There is no information about parental investment in southern watersnakes in the literature. However, females invest substantially in protecting the young in their cloaca during development and providing resources to the embryo. After birth, the young become independent. (Ernst and Ernst, 2003)
In general, southern watersnakes mature by the age of 3 and can live up to 7 or 8 years. The lifespan of southern watersnakes is dependent on the quality and the quantity of their food. A male and female member both survived captivity for 3 years and 3 months. In general, individual southern watersnakes do not live long in captivity. (Ernst and Ernst, 2003; Nielsen, 2011)
The literature suggests that southern watersnakes are similar in behavior to other water snakes. Their movement patterns are suggested to be very similar to northern watersnakes, Nerodia sipedon. They use lateral undulatory movement and sidewinding for crawling on the ground. Most watersnakes swim with their bodies fully submerged in water. Individuals also flick their tongues in order to gather chemical stimuli from the environment. They are active both during the day and at night. In winter, they can be found hibernating beneath logs or rocks or in burrows. During periods of extreme drought, southern watersnakes will leave the area, possibly to find a more suitable aquatic habitat. It has been suggested that they are driven away from an area affected by drought primarily because of the reduced water levels as well as reduced levels of aquatic prey. Although their numbers may initially drop during a drought period, these snakes recover substantially afterwards because these snakes have a high fecundity rate. (Daghfous, et al., 2012; Dorcas and Gibbons, 2004; Ernst and Ernst, 2003; Seigel, et al., 1995; Willson, et al., 2006)
Home range size is not reported in the literature.
Snakes use their sense of sight, smell, and touch to navigate. They use visual and olfactory cues to recognize predators, prey, and their environment. Southern watersnakes flick their tongue in order to collect smells from the environment, such as the scent of a nearby food item. There have not been many studies, though, that focus solely on communication and perception in this species, but snakes generally use pheromones in order to attract mates. (Daghfous, et al., 2012; Ernst and Ernst, 2003; Mason, et al., 1989)
Southern watersnakes are dietary generalists that undergo ontogenetic changes from eating primarily fish as juveniles to eating mainly frogs or large fish as adults. Young stay on a fish diet until they are about 6 months old. The type of fish and amphibians that they consume will largely depend on the particular area they inhabit, but some prey include American eels (Anguilla rostrata), pirate perch (Aphredoderus sayanus), banded pygmy sunfish (Elassoma zonatum), American pickerel (Esox americanus), topminnows (Fundulus species), western mosquitofish (Gambusia affinis), least killifish (Heterandria formosa), white catfish (Ameiurus catus), bluegill sunfish (Lepomis macrochirus), spotted sunfish (Lepomis punctatus), rainwater killifish (Lucania parva), bass (Micropterus species), golden shiners (Notemigonus crysoleucas), southern toads (Anaxyrus terrestris), spring peepers (Pseudacris crucifer), gopher frogs (Lithobates capito), and red-spotted newts (Notophthalmus viridescens). On occasion, they prey on small turtles, small snakes, birds, earthworms, and crayfish. The enlarged gape of snakes allows them to consume large prey, but southern watersnakes have a difficult time ingesting prey items that are relatively heavy, short, and wide. (Dorcas and Gibbons, 2004; Ernst and Ernst, 2003; Vincent, et al., 2006)
Southern watersnakes are primarily preyed on by other snakes, great blue herons (Ardea herodias), and alligators (Alligator mississippiensis). In order to avoid predation, individuals escape into the water, enlarge their posterior head region, bite repeatedly, or secrete a foul musk. They are also cryptically colored, which makes them harder to find for predators. (Dorcas and Gibbons, 2004; Vincent, et al., 2006)
Southern watersnakes control populations of fish and amphibians. Florida watersnakes (N. f. pictiventris) are carriers of the parasite hemogregarines (Hepatozoon species), which is one of the most common blood parasites among snakes. (Vincent, et al., 2006; Wozniak, et al., 1998)
Southern watersnakes are important predators of amphibians and fish in aquatic habitats. (Vincent, et al., 2006)
There are no known adverse effects of these snakes on humans.
Southern watersnakes are not threatened. They are abundant in appropriate habitat and dietary generalists. Southern watersnakes are an ideal species to study in order to assess environmental conditions, such as water quality. For instance, they have been used as focal studies in research studying the effects of exposure to coal combustion wastes on metabolic rates. (Dorcas and Gibbons, 2004; Hopkins, et al., 1999)
Agkistrodon piscivorous) despite the differences in their physical appearance. As a result, many southern water snakesare mistakenly killed by humans. (Krysko and King, 2010)is often mistaken for venomous cottonmouths (
Annette Califano (author), The College of New Jersey, Keith Pecor (editor), The College of New Jersey, Tanya Dewey (editor), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.
an animal that mainly eats meat
uses smells or other chemicals to communicate
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature
parental care is carried out by females
union of egg and spermatozoan
mainly lives in water that is not salty.
having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.
the state that some animals enter during winter in which normal physiological processes are significantly reduced, thus lowering the animal's energy requirements. The act or condition of passing winter in a torpid or resting state, typically involving the abandonment of homoiothermy in mammals.
Animals with indeterminate growth continue to grow throughout their lives.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
marshes are wetland areas often dominated by grasses and reeds.
having the capacity to move from one place to another.
specialized for swimming
the area in which the animal is naturally found, the region in which it is endemic.
active during the night
reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.
chemicals released into air or water that are detected by and responded to by other animals of the same species
an animal that mainly eats fish
breeding is confined to a particular season
remains in the same area
reproduction that includes combining the genetic contribution of two individuals, a male and a female
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
uses touch to communicate
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
movements of a hard surface that are produced by animals as signals to others
uses sight to communicate
young are relatively well-developed when born
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