VENOMOUS

Other common names

Cottonmouth, Cottonmouth Moccasin, Water Moccasin, Moccasin

Basic description

The average adult Florida cottonmouth is 30-48 inches (76-122 cm) in total length. This snake is heavy bodied with a pattern of light brown and dark brown crossbands containing many dark spots and speckles. The pattern darkens with age so adults may become uniformly black. The eye is camouflaged by a broad, dark, facial stripe. The color pattern of juvenile cottonmouths is much lighter than in adults, and newborns have a sulfur-yellow tail tip.

Range

Cottonmouths are found throughout Florida and in every county. They also occur on many nearshore islands including the Upper Florida Keys and several islands in the Gulf of Mexico in Levy (e.g., Cedar Keys) and Franklin (e.g., Dog, St. George, and St. Vincent islands) counties.

Assessment of risk to people and pets

VENOMOUS Cottonmouth bites can be very dangerous to people and pets. The victim should seek immediate medical care from a physician or hospital experienced in treating snakebites. Cottonmouths are not aggressive and avoid direct contact with people and pets. Most bites occur when the snakes are intentionally molested or accidentally stepped on.

Comparison with other species

There are eight species of non-venomous watersnakes (species in the genus Nerodia) in Florida that overlap with cottonmouths in distribution and habitat, and all of them resemble cottonmouths. However, there are some differences you can look for in general to help distinguish cottonmouths from watersnakes:

  • If the head is viewed from directly above, the eyes of cottonmouths cannot be seen, whereas the eyes of watersnakes are visible.
  • Cottonmouths have vertically elliptical (cat-like) pupils whereas watersnakes have round pupils.
  • Cottonmouths have a facial pit organ between the nostril and the eye, whereas watersnakes do not have this organ.
  • Watersnakes usually have thin dark vertical lines on the sides of the face near the mouth, whereas the cottonmouths have no such dark lines.
  • Lastly, cottonmouths typically rest with their heads elevated off the ground and tilted upwards at an angle, whereas watersnakes typically do not rest with their heads tilted upwards at an angle.

Eastern Copperhead (Agkistrodon contortrix) Venomous Brightly-colored juvenile Florida Cottonmouths are sometimes mistaken for the Eastern Copperhead (Agkistrodon contortrix), which occurs in Florida only in the Panhandle. The dark crossbands on the body of juvenile cottonmouths have numerous dark spots and speckles, whereas the dark crossbands on copperheads have no dark spots or at most only one. Adult copperheads maintain their juvenile color pattern, whereas adult cottonmouths are typically uniformly dark with very little discernable pattern. Each eye of the copperhead is not obscured by the dark facial band typical of the cottonmouth.

Side by side comparison of Eastern Copperhead and Florida Coppermouth
Eastern Copperhead. Photo courtesy of bobbyfingers/iNaturalist
Florida Cottonmouth. Photo courtesy of Luke Smith.

Here is a list of the species of watersnakes in Florida:

Saltmarsh Snake (Nerodia clarkii) Non-venomous

Side by side comparison of a Saltmarsh watersnake - thin brown snake with pale stripes and a Florida Cottonmouth - coiled snake with its head raised
Saltmarsh Watersnake. Photo courtesy of Luke Smith.
Florida Cottonmouth. Photo courtesy of Luke Smith

Mississippi Green Watersnake (Nerodia cyclopion) Non-venomous

Side by side comparison of a Mississippi Green Watersnake and a Florida Cottonmouth
Mississippi Green Watersnake. Photo courtesy of Eric B.
Florida Cottonmouth. Photo courtesy of Luke Smith

Plain-bellied Watersnake (Nerodia erythrogaster) Non-venomous

Side by side comparison of a Plain-bellied watersnake and a Florida Cottonmouth.
Plain-bellied Watersnake. Photo courtesy of Jake Scott
Florida Cottonmouth. Photo courtesy of Luke Smith.

Southern Watersnake(Nerodia fasciata) Non-venomous

Side by side comparison of a Southern Watersnake and a Florida Cottonmouth.
Southern Watersnake performing defensive head flattening. Photo courtesy of Luke Smith.
Florida Cottonmouth. Photo courtesy of Luke Smith.

Florida Green Watersnake (Nerodia floridana) Non-venomous

Side by side comparison of a Florida Green Watersnake and a Florida Cottonmouth.
Florida Green Watersnake. Photo courtesy of johnjinjohny/iNaturalist
Florida Cottonmouth. Photo courtesy of Luke Smith.

Diamond-backed Watersnake (Nerodia rhombifer) Non-venomous

Diamond-backed Watersnake. Photo courtesy of kaptiankory/iNaturalist
Florida Cottonmouth. Photo courtesy of Luke Smith

Midland Watersnake (Nerodia sipedon pleuralis) Non-venomous

Brown Watersnake (Nerodia taxispilota) Non-venomous

Share your observations

You can help scientists better understand the biology and distribution of this species by sharing your observations. Send photos or videos of interesting observations, along with associated information, by emailing the herpetology staff at the Florida Museum for documentation in the Museum’s Herpetology Master Database. You can also post your observations on iNaturalist.

Additional helpful information

Do you have snakes around your house? Learn how to safely co-exist with snakes.

Still have questions about snakes or identifications? Feel free to email the herpetology staff at the Florida Museum with your questions or feedback on this profile.

Banner photo courtesy of Luke Smith. Please credit any photographers on the page and see our copyright policy.