Reference

Snake glossary

The terms used across this field guide, in plain English. If a word in a species entry is unfamiliar, you will likely find it here.

Venom and danger

Venomous: Able to inject toxins into another animal through a bite or sting. Snakes are venomous, not poisonous, they deliver venom rather than being harmful to eat or touch.
Poisonous: Harmful when eaten, inhaled, or absorbed. Almost no snakes are poisonous; the word is commonly misused for venomous snakes.
Hemotoxic venom: Venom that damages blood, blood vessels, and tissue, causing swelling, bleeding, and pain. Typical of vipers such as rattlesnakes and copperheads.
Neurotoxic venom: Venom that disrupts the nervous system, which can affect breathing and muscle control. Typical of elapids such as cobras, coral snakes, and kraits.
Antivenom: A medicine made from antibodies that neutralizes snake venom. It is the primary hospital treatment for a serious venomous bite and works best when given early.
Dry bite: A bite in which a venomous snake injects little or no venom. Dry bites still require medical evaluation because envenomation can be delayed or hard to judge.
Envenomation: The medical term for venom being injected into the body by a bite or sting.

Scale and head features are the most reliable way to tell similar snakes apart.

Keeled scales: Scales with a raised ridge down the center, giving the snake a rough, matte look. Many watersnakes and gartersnakes are keeled; smooth-scaled snakes look glossy.
Dorsal: Relating to the back or upper surface of the snake. 'Dorsal pattern' means the markings along the top of the body.
Ventral: Relating to the belly or underside. The ventral scales are the wide plates a snake uses to grip and move.
Vertical (elliptical) pupils: Cat-like, slit-shaped pupils. In the United States most pit vipers have vertical pupils, while most harmless snakes have round pupils, though this is not a universal rule worldwide.
Heat-sensing pit: A small opening between the eye and nostril that detects warmth, used by pit vipers (rattlesnakes, copperheads, cottonmouths) to locate prey. Its presence marks a pit viper.
Loreal pit: Another name for the heat-sensing pit of a pit viper.
Anal plate: The scale covering the vent, near the base of the tail. Whether it is single or divided is used by experts to identify some species.
Rattle: Interlocking, hollow segments of keratin at the tip of a rattlesnake's tail that buzz as a warning. A new segment is added each time the snake sheds.

Banded: Marked with rings or bars of color that wrap across the body, as in many kingsnakes and coral snakes.
Blotched: Marked with large, irregular patches along the back, as in many ratsnakes and bullsnakes.
Saddle: A blotch that is wider across the back and narrows on the sides, resembling a saddle.
Hourglass crossband: A band that is wide on the sides and pinched narrow over the spine, the classic copperhead marking, the opposite of most harmless lookalikes.
Keelback: A common name applied to various keeled, often water-associated snakes, especially in Asia and Africa.

Ambush predator: A snake that waits motionless for prey to come near, rather than actively hunting it down. Many vipers hunt this way.
Constrictor: A snake that kills prey by coiling around it and tightening, stopping blood flow. Pythons, boas, kingsnakes, and ratsnakes are constrictors.
Musk: A foul-smelling fluid many snakes release from glands near the tail when handled, used as a defense.
Brumation: The reptile equivalent of hibernation, a period of winter dormancy when snakes become inactive in cold weather.
Caudal luring: Wiggling the tail to imitate a worm or insect and draw prey within striking range. Some young vipers do this.
Gravid: Carrying eggs or developing young; the snake equivalent of pregnant.

Oviparous: Egg-laying. The female deposits eggs that develop and hatch outside her body.
Viviparous: Giving birth to live young rather than laying eggs. Many vipers and gartersnakes are live-bearing.
Genus: A group of closely related species. It is the first word of the two-part scientific name, for example, Crotalus in Crotalus atrox.
Family: A broader group of related genera. Major snake families include Viperidae (vipers), Elapidae (cobras, coral snakes), and Colubridae (most harmless snakes).
Endemic: Native to, and found only in, one region. An endemic snake occurs nowhere else in the world.
Range: The geographic area where a species naturally occurs.