Couleuvre d'eau du Nord— Quebec wildlife

The common watersnake (Nerodia sipedon) 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 venomous cottonmouth (Agkistrodon piscivorus).

Description

The common watersnake can grow up to 135 cm (4 ft 5 in) in total length (including tail). Per one study, the average total length of females was 81.4 cm (2 ft 8 in), while that of males was 69.6 cm (2 ft 3+1⁄2 in). From known studies of this species in the wild, adult females can weigh between 159 and 408 g (5+1⁄2 and 14+1⁄2 oz) typically, while the smaller male can range from 80.8 to 151 g (2+7⁄8 to 5+3⁄8 oz). The largest females can weigh up to 560 g (20 oz) while the largest males can scale 370 g (13 oz). 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; attempting to kill snakes greatly increases the chance of being bitten. 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.

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 19–23 cm (7+1⁄2–9 in) long. 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. 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. Males typically reach sexual maturity during their second year, generally around 21 months. 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. Rarely, and observed only in captivity, the northern watersnake can reproduce by facultative parthenogenesis.