M
Species Profile

Moccasin Snake

Agkistrodon piscivorus

White-mouth warning of the wetlands
Kristian Bell/Shutterstock.com

Moccasin Snake Distribution

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Endemic Species
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Found in 14 states/provinces

Moccasin Snake

At a Glance

Wild Species
Also Known As moccasin, black moccasin, swamp moccasin, water rattler, mocasin de agua
Diet Carnivore
Activity Cathemeral+
Lifespan 12 years
Weight 2 lbs
Status Least Concern
Did You Know?

Adults are commonly ~80-100 cm total length; large individuals can exceed 150 cm (exceptional records approach ~180 cm).

Scientific Classification

A venomous North American pit viper commonly known as the cottonmouth or water moccasin, noted for its defensive display of a pale/white mouth interior.

Kingdom
Animalia
Phylum
Chordata
Class
Reptilia
Order
Squamata
Family
Viperidae
Genus
Agkistrodon
Species
Agkistrodon piscivorus

Distinguishing Features

  • Pit viper with heat-sensing facial pits between eye and nostril
  • Often heavy-bodied with keeled scales; pattern may be banded in juveniles and darken with age
  • Characteristic threat display: gaping with a bright white mouth lining (“cottonmouth”)
  • Semi-aquatic habits; frequently encountered near water

Physical Measurements

Males and females differ in size

Length
♂ 3 ft 3 in (1 ft 12 in – 6 ft)
♀ 3 ft 3 in (2 ft 4 in – 5 ft 11 in)
Weight
♂ 2 lbs (1 lbs – 5 lbs)
♀ 2 lbs (1 lbs – 4 lbs)
Tail Length
♂ 6 in (3 in – 9 in)
♀ 6 in (4 in – 10 in)
Top Speed
2 mph
slithering
Venomous

Appearance

Primary Colors
Brown Black
Secondary Colors
Tan Cream White
Skin Type Dry, keratinized scales; strongly keeled dorsal scales typical of pit vipers.
Distinctive Features
  • Venomous North American pit viper (Viperidae) with heat-sensing loreal pits between eye and nostril.
  • Stout-bodied with broad, blocky/triangular head and distinct neck; vertical (elliptical) pupils.
  • Adult total length commonly 76-91 cm; reported maximum about 183 cm.
  • Defensive display often includes coiling and gaping to show the pale/white mouth lining ("cottonmouth").
  • Semi-aquatic wetland ecology; commonly encountered near swamps, marshes, slow streams, and pond margins; capable swimmer.
  • Juveniles often have a bright yellow tail tip used for caudal luring.
  • High-level distinction from many nonvenomous Nerodia water snakes: cottonmouths have loreal pits and typically a heavier build and blockier head; adults often become uniformly dark, while many Nerodia retain clearer patterns.

Sexual Dimorphism

Males average larger overall and have proportionally longer, thicker tails due to hemipenes. Females are typically shorter with shorter tails and may appear more robust when gravid.

♂
  • Often longer total length and heavier body mass than females of similar age.
  • Tail longer relative to body length; tail base thicker.
  • More frequent and pronounced tail-tip luring reported in juveniles (sex not always obvious).
♀
  • Typically shorter total length; tail shorter relative to body length.
  • Body may appear broader during gravidity (seasonal).
  • Cloacal region/tail base less thick than males.

Did You Know?

Adults are commonly ~80-100 cm total length; large individuals can exceed 150 cm (exceptional records approach ~180 cm).

Newborns are typically ~20-25 cm long and are born live (no eggs laid).

Litters are usually 1-16 young (often ~5-9), born late summer to early fall.

Juveniles often have a yellow-green tail tip and may "caudal lure," wriggling it like a worm to attract prey.

Like other pit vipers, it has heat-sensing facial pits that detect warm-bodied prey even in low light.

Documented longevity exceeds two decades in captivity (records ~24 years are reported).

The defensive "gape" (wide open mouth showing pale lining) is a hallmark threat display and the source of the name "cottonmouth."

Unique Adaptations

  • Infrared-sensing loreal pits: paired organs between eye and nostril that help target endothermic prey and guide strikes in dim conditions.
  • Long, hinged solenoglyphous fangs: fold against the palate when not in use and rotate forward during a strike-typical of Viperidae but central to cottonmouth feeding/defense.
  • Semi-aquatic performance: strong swimming ability and willingness to feed on aquatic prey (fish/amphibians) makes it one of the most wetland-associated North American vipers.
  • High-contrast threat signal: the pale oral lining functions as a conspicuous warning when the snake gapes-an escalation display that can deter predators without a bite.
  • Ontogenetic color shift: juveniles are often more strongly banded with a bright tail tip; adults commonly darken, which can improve camouflage in tannic swamps and shaded wetlands.

Interesting Behaviors

  • Defensive gaping display: raises the head, opens the mouth wide to show the pale interior; may hold this posture while slowly rocking the head.
  • Semi-aquatic hunting: patrols shorelines and shallow water, taking fish and amphibians; also ambushes at the water's edge.
  • Basking and ambush from structure: frequently uses logs, banks, and low vegetation as daytime basking sites and hunting platforms.
  • Caudal luring (especially juveniles): tail-tip twitching can draw frogs/lizards within strike range.
  • Seasonal activity shifts: more crepuscular/nocturnal in hot weather; more diurnal during cooler periods.
  • In-place defense rather than rapid flight: often stands its ground compared with many nonvenomous water snakes, which more readily flee.

Cultural Significance

Cottonmouth (Water Moccasin) (Agkistrodon piscivorus) is a defining swamp animal in the southeastern United States. It appears in warning tales, signs, and nature writing as a sign of wetland wildness and danger. People often call any waterside snake a 'water moccasin', causing confusion with harmless Nerodia water snakes.

Myths & Legends

Southern U.S. river-and-swamp folklore often tells of "water moccasins" that will chase intruders back to shore or pursue boats-an enduring campfire story tied to their tendency to hold ground and display rather than quickly flee.

In parts of the American South, the term "moccasin snake" became a generic folk name for dangerous waterside serpents, blending Indigenous-origin naming (moccasin as a word adopted into English) with settler-era swamp lore.

Cherokee tales about powerful water snakes, sometimes told as horned or giant river snakes, are now often linked to real swamp snakes people fear, like the cottonmouth (water moccasin, Agkistrodon piscivorus), to explain avoiding backwaters.

Regional hunting and fishing oral traditions include "log-that-bites" tales-snakes mistaken for driftwood that suddenly reveal a white mouth-stories that mirror the cottonmouth's habit of basking on logs and its conspicuous gape display.

The name "cottonmouth" itself functions as a modern naming legend: repeated storytelling about the 'white-cotton warning' reinforces the idea that the snake announces itself before striking, shaping how people interpret encounters in the field.

Conservation Status

LC Least Concern

Widespread and abundant in the wild.

Population Stable

Protected Under

  • Not listed under the U.S. Endangered Species Act (ESA); management primarily occurs under state wildlife regulations (varies by state).
  • Protected from take within many U.S. National Parks and National Wildlife Refuges under site-specific regulations (e.g., prohibitions on wildlife harassment/collection).

Life Cycle

Birth 7 neonates
Lifespan 12 years

Lifespan

In the Wild
5–20 years
In Captivity
10–24 years

Reproduction

Mating System Promiscuity
Social Structure Solitary
Breeding Pattern Transient
Fertilization Internal Fertilization
Birth Type Internal_fertilization

Solitary pit viper; males engage in combat and search for receptive females during spring (and sometimes fall) breeding seasons. Internal fertilization; females can store sperm and give live birth ~5 months later, typically 5-9 (range 1-16) neonates; no parental care (Ernst & Ernst 2003).

Behavior & Ecology

Social Aggregation Group: 1
Activity Cathemeral, Nocturnal, Crepuscular
Diet Carnivore Fish and amphibians (especially shallow-water fish and frogs)
Seasonal Hibernates

Temperament

Most individuals avoid confrontation; propensity to stand ground increases when cornered or handled.
Defensive display includes mouth-gaping to show pale oral lining; body coiling and head elevation are common.
Often relies on crypsis and immobility; may retreat to water and swim when disturbed in riparian habitats.
Biting typically defensive; venom delivery possible even with short strikes at close range.
Longevity: maximum recorded 24.7 years in captivity (AnAge database: Agkistrodon piscivorus).

Communication

Hissing (forced-air exhalation) during defensive encounters.
Chemical: pheromone trail-following and mate recognition via vomeronasal (tongue-flick) sampling.
Visual: open-mouth gaping threat display; posture changes (tight coils, head elevation) signal defensiveness.
Tactile: body contact during courtship; males may engage in ritualized combat for access to females.
Vibrational: tail vibration against substrate when threatened Often without a true rattle

Habitat

Wetland Swamp Marsh River/Stream Lake Pond Estuary Coastal Deciduous Forest Coniferous Forest Woodland Agricultural/Farmland Suburban Urban +8
Biomes:
Wetland Freshwater Marine Temperate Forest
Terrain:
Coastal Riverine Plains Valley Muddy Sandy
Elevation: Up to 1640 ft 5 in

Ecological Role

Semiaquatic mesopredator in southeastern U.S. wetlands and riparian systems

Regulates populations of small fish, amphibians, and other wetland vertebrates (top-down control) Contributes to energy/nutrient transfer between aquatic and terrestrial food webs via shoreline predation Removes weakened or dead animals when scavenging (localized carrion processing) Serves as prey for higher-level predators (e.g., wading birds, raptors, large snakes, alligators), supporting wetland trophic structure

Diet Details

Main Prey:
Fish Amphibians Reptiles Birds Mammals Invertebrates Carrion +1

Human Interaction

Domestication Status

Wild

Agkistrodon piscivorus (cottonmouth/water moccasin) is a wild North American pit viper and is not domesticated. People sometimes keep it in zoos or for research, but that is not domestication. Human interactions include accidental bites, killing from fear, medical care/antivenom, education, research, and more encounters when people change wetlands.

Danger Level

High
  • Venomous bite with potentially severe local tissue injury (pain, swelling, blistering/necrosis in some cases) and systemic effects typical of pit-viper envenomation (coagulopathy/bleeding abnormalities, hypotension, nausea).
  • Highest risk during accidental close-range encounters (stepping on/near the snake along shorelines, wetlands, brushy edges), handling attempts, or intentional harassment/killing.
  • Bites can be medically significant and may require hospital evaluation and antivenom; untreated or delayed treatment can lead to complications (secondary infection, compartment-like swelling syndromes, prolonged coagulopathy).
  • Fatalities are uncommon with modern care but remain possible, especially with delayed treatment, large venom dose, or vulnerable patients (children, older adults, comorbidities).

As a Pet

Not Suitable as Pet

Legality: Keeping Cottonmouth (Water Moccasin, Agkistrodon piscivorus) is highly restricted. In the U.S. many places ban or require permits, secure cages, or proof of experience. Laws vary—check state and local rules.

Care Level: Expert Only

Purchase Cost: $150 - $600
Lifetime Cost: $5,000 - $30,000

Economic Value

Uses:
Education and public outreach Ecotourism/wildlife viewing Biomedical and toxinology research Public health (antivenom/clinical toxicology relevance) Ecosystem services (predation on small mammals)
Products:
  • venom for research and antivenom-related work (regulated, typically via institutions)
  • educational programming/exhibits (zoos, nature centers)
  • scientific data/specimens (museum collections, field studies)

Relationships

Predators 8

American alligator
American alligator Alligator mississippiensis
Eastern kingsnake Lampropeltis getula
Red-tailed hawk Buteo jamaicensis
Bald eagle
Bald eagle Haliaeetus leucocephalus
Great blue heron
Great blue heron Ardea herodias
Raccoon
Raccoon Procyon lotor
Virginia opossum Didelphis virginiana
Coyote
Coyote Canis latrans

Related Species 9

Copperhead
Copperhead Agkistrodon contortrix Shared Genus
Broad-banded copperhead Agkistrodon laticinctus Shared Genus
Cantil
Cantil Agkistrodon bilineatus Shared Genus
Taylor's cantil Agkistrodon taylori Shared Genus
Cuban moccasin Agkistrodon russeolus Shared Genus
Eastern diamondback rattlesnake
Eastern diamondback rattlesnake Crotalus adamanteus Shared Family
Timber rattlesnake
Timber rattlesnake Crotalus horridus Shared Family
Pygmy rattlesnake
Pygmy rattlesnake Sistrurus miliarius Shared Family
Eastern massasauga
Eastern massasauga Sistrurus catenatus Shared Family

Ecological Equivalents 5

Animals that fill a similar ecological role in their ecosystem

Common watersnake Nerodia sipedon Often found in the same freshwater habitats and hunts similar prey (fish and amphibians). It is often confused with Agkistrodon piscivorus because it is semi-aquatic, ambushes prey, and gapes to show a pale mouth.
Banded watersnake
Banded watersnake Nerodia fasciata Occurs in coastal plain swamps and marsh edges and strongly overlaps in diet (fish and frogs) as well as in basking and shoreline-hunting behavior. Both are robust-bodied snakes that use aquatic cover and employ strike-and-hold feeding (Nerodia are nonvenomous).
Green watersnake Nerodia cyclopion Occupies similar lowland swamp habitats (often heavily vegetated, slow-moving waters) and targets similar prey assemblages. Similar body plan and habitat use can lead to confusion where ranges overlap in the Gulf Coastal Plain.
Eastern diamondback rattlesnake
Eastern diamondback rattlesnake Crotalus adamanteus Shares the broader Southeastern Coastal Plain with Agkistrodon piscivorus (cottonmouth) as a sit-and-wait venomous predator, but is more associated with upland pine flatwoods while the cottonmouth is strongly tied to aquatic edges. Both species display defensive posturing and rely on venom to subdue vertebrate prey.
American alligator
American alligator Alligator mississippiensis Co-occurs in wetlands and shares prey (fish, frogs, birds, small mammals). Both occupy similar wetland apex-predator feeding roles; American alligators may eat cottonmouths, while cottonmouths also eat small aquatic animals in waters inhabited by alligators.

“When it feels threatened, this snake reveals its fangs and puffy, white mouth”

Cottonmouth is among the many alternative names of the moccasin snake. It is a venomous snake living in the southeastern region of the United States. They are carnivores eating turtles, fish, frogs, snakes, and other small prey. Baby moccasin snakes are vulnerable to attack by snapping turtles, cats, and raccoons in their habitat. These snakes can live up to 25 years.

3 Moccasin Snake Amazing Facts

• They can bite and eat prey underwater
• Their venomous bite can cause tissue damage and bleeding
• A female holds her fertilized eggs inside her body until it’s time for them to hatch

Where to Find Moccasin Snake

The moccasin snake lives in North America in the southeastern region of the United States. Its range runs east from Texas and Oklahoma to the southern part of Virginia. It’s also seen in southern Indiana and Missouri.

Their habitat includes wetlands, forests, the plains, rivers, and lakes. They take shelter in hollow logs and beneath leaf debris. On hot days, they move onto rocks and ledges to sun themselves.

In the extreme northern parts of their range, moccasin snakes go into brumation in the wintertime. These snakes are especially active in the spring during their breeding season.

Types of Moccasins Snakes

Moccasin snakes belong to the Agkistrodon genus. The Agkistrodon piscivorus is in the Viperidae (viper) family. The other members of this genus are venomous as well.

Some examples:

• Cantil (Agkistrodon bilineatus)-This snake is sometimes called the Mexican moccasin or the Mexican ground pit viper. It lives in Mexico and further down into Central America. This snake is a little shorter in length than other moccasin snakes at an average of 24 inches.
• Florida cottonmouth (Agkistrodon conanti)-The Florida cottonmouth shares much of the same wetland habitat in the southeastern United States as the Agkistrodon piscivorus. Though its length ranges from 30-48 inches, this snake can grow to a length of six feet!
• Yucatecan cantil (Agkistrodon russeolus)-Instead of having black scales, this viper is deep reddish brown in color. It’s found on the Yucatan Peninsula in Mexico and in Belize in Central America.

Moccasin Snake Scientific Name

Its scientific name is Agkistrodon piscivorus. Agkistrodon is a Greek word translating loosely to fish hook and piscivorus translates to fish eater. So, its scientific name refers to its fangs and eating habits.

When it comes to alternate names this snake has a lot of them! It’s called a viper, a cottonmouth, black moccasin, or a water moccasin.

It belongs to the Viperidae family and the class Reptilia.

Until a few years ago, cottonmouths were all considered subspecies of A. piscivorus. However, genetic testing showed that there are two subspecies but that the Florida water moccasin is genetically distinct.

  • Northern cottonmouth (Agkistrodon piscivorus piscivorus)
  • Western cottonmouth (Agkistrodon piscivorus leucostoma)
  • Florida cottonmouth (Agkistrodon conanti)

Moccasin Snake Population and Conservation Status

Though researchers are unsure about the exact population of the moccasin snake, they believe there are over 100,000 adults. This snake’s population is categorized as stable, and its conservation status is listed as Least Concern by the IUCN Redlist.

How to Identify a Moccasin Snake: Appearance and Description

A moccasin snake has black scales on its back featuring either light or dark brown crossbands. Its head is light brown or olive, and it has an underside of gray or light brown with dark blotches. This snake has a black stripe located near each eye. Its eyes have vertical pupils, and its head is triangular. There is a thin white line on its upper lip as well.

The length of an adult moccasin snake ranges from 30 to 42 inches. Adults can weigh up to ten pounds.

How to identify a moccasin snake:
• A black body with a dark brown or olive-green head
• A dark horizontal stripe near each eye
• Dark or light brown crossbands on its back
• A gray or tan underside with a pattern of dark blotches
• A white line on its upper lip
• A triangular shaped head and eyes with vertical pupils

Moccasin vs. Cottonmouth

In comparing these two snakes, you’ll need to know one thing right away. They are the same snake! The moccasin snake goes by many other names including cottonmouth snake. It’s called a cottonmouth because of the puffy, bright white interior of its mouth.

This reptile’s bite can inject powerful venom into its prey or a human. It lives in the southeastern United States in marshes, forests, and wetlands.

Moccasin Snake Venom: How Dangerous Are They?

Moccasin snakes are venomous. A bite from this snake can contain venom that damages tissue and causes severe pain.

If someone gets a bite from a moccasin snake, it’s important to get to the emergency room or call for an ambulance. Once the ambulance is called, keep the injured person as still as possible, give them water, and put a blanket over them for warmth.

These snakes have potent venom that’s usually not deadly, but there’s always a risk. At the medical facility, the person is likely to get antivenin along with topical treatment to help relieve the pain of the bite.

Moccasin Snake Behavior and Humans

Moccasin snakes live in a marshes or wetlands. If they live in a forest habitat, it’s not far from a body of water such as a pond, lake, or stream. These snakes spend time in the water and on land. So, a person walking trails in the woods or fishing in a lake may encounter a moccasin snake.

The moccasin snake is sometimes thought of as an aggressive snake. This is likely due to its habit of revealing its fangs and the puffy white interior of its mouth. However, this snake opens its mouth in an effort to scare away predators. It doesn’t want to confront a threat. Though it has a powerful venom, the moccasin snake is more likely to try to escape than strike. In short, despite their fearsome, open-mouthed behavior, these are not aggressive snakes.

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Sources

  1. https://www.tn.gov/twra/wildlife/reptiles/snakes/cottonmouth.html
  2. https://www.iucnredlist.org/species/64298/12756313
  3. https://en.wikipedia.org/wiki/Agkistrodon_piscivorus
  4. https://ufwildlife.ifas.ufl.edu/water_moccasin_watersnake_comparison.shtml
  5. https://wildlifeinformer.com/water-moccasin-vs-cottonmouth/
  6. https://animalsake.com/water-moccasin-snake
  7. https://en.wikipedia.org/wiki/Agkistrodon_bilineatus
  8. https://hgic.clemson.edu/factsheet/identifying-copperhead-snakes/
Austin S.

About the Author

Austin S.

Growing up in rural New England on a small scale farm gave me a lifelong passion for animals. I love learning about new wild animal species, habitats, animal evolutions, dogs, cats, and more. I've always been surrounded by pets and believe the best dog and best cat products are important to keeping our animals happy and healthy. It's my mission to help you learn more about wild animals, and how to care for your pets better with carefully reviewed products.
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Moccasin Snake FAQs (Frequently Asked Questions)

Yes, they have venom that can cause extreme pain and tissue damage. Fortunately, its venomous bite rarely results in the death of a human.

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