The Water Moccasin, also known as the Cottonmouth, is a venomous pit viper native to the southeastern United States (Agkistrodon piscivorus). This species does not lay eggs. Instead, the Water Moccasin gives birth to live young, a reproductive method that differs significantly from egg-laying snakes, allowing the developing offspring to remain protected inside the mother’s body.
Live Birth: The Reproductive Strategy
Water Moccasins use a form of live birth known as ovoviviparity. The young develop inside eggs retained within the mother’s body, relying entirely on the yolk sac for sustenance. There is no direct placental connection for nourishment. The eggs “hatch” inside the female, and she then gives birth to fully formed, live snakes.
Mating typically occurs during the spring months, and the female retains the developing embryos for a gestation period lasting approximately four to five months. The timing of birth is highly seasonal, with the young usually emerging in late summer or early fall, specifically from August through October. Litters can range from one to 20 offspring, though the most common size is a clutch of six to eight neonates.
Ovoviviparity allows the mother to regulate the environment for her young by moving to warmer or cooler areas, protecting the developing embryos from predators and temperature extremes. Since development occurs internally, the female is not required to find a suitable nesting site for external incubation. Females generally reproduce every two to three years, as carrying and birthing a litter is energetically substantial.
Neonates: Appearance and Behavior
Newborn Water Moccasins are immediately independent. They are born relatively small, measuring about 6 to 11 inches long, and are notably more colorful than their adult counterparts. The body pattern features distinct, bright reddish-brown or tan crossbands against a lighter background, a coloration that darkens and fades as the snake matures.
The tip of the young Moccasin’s tail is a bright sulfur-yellow or greenish-yellow color. This caudal lure is wiggled to imitate a worm or grub, attracting small prey like frogs or fish. This feeding strategy is unique to the young snakes and is often lost as they grow older and their diet shifts.
Neonates are born with fully functional fangs and a complete supply of venom. They are venomous from the moment of birth, posing the same hazard as an adult snake despite their small size. Although their venom glands contain less volume than an adult’s, the young snakes deliver toxic, cytotoxic venom that destroys tissue.
Why the Confusion About Snake Eggs
Confusion about Water Moccasin reproduction stems from the fact that most snake species in the world are egg-layers, a reproductive mode known as oviparity. Approximately 70% of all snake species, including common species like rat snakes and pythons, reproduce by depositing shelled eggs that hatch externally. It is a reasonable assumption for the public to believe all snakes follow this pattern.
Snakes are separated into two main groups: oviparous (egg-laying) and viviparous (live-bearing, which includes ovoviviparity). Live-bearing snakes are more common in colder climates or aquatic environments, where external eggs would be vulnerable to low temperatures or flooding. Many other North American water snakes, such as the harmless species in the genus Nerodia often confused with the Moccasin, are also live-bearers.
The Water Moccasin belongs to the pit viper family, Crotalinae, which includes rattlesnakes and copperheads, and nearly all species within this family are live-bearers. This evolutionary trait of internal development is a successful adaptation for these snakes, offering protection and mobility during the vulnerable incubation period.