Rattlesnakes – an Overview of the Most Highly Evolved Serpents

The subjects of today’s article, while not suitable pets under any circumstances, still hold great interest for reptile enthusiasts. Today we’ll take a look at some of their unique characteristics.

Rattlesnake Central

Growing up in NYC, I had the distinct pleasure of easy access to the Staten Island Zoo’s Reptile House, which was lorded over by the man known worldwide for introducing a generation of aspiring herpetologists to snake keeping – Carl Kauffeld. At the time, the zoo boasted a collection containing every known Rattlesnake species. Several years ago, I was thrilled to be chosen as consultant on the Reptile House renovation, and today Rattlesnakes again take center stage there (please see photo below).

Classification and Range

Rattlesnakes and their relatives, collectively known as Pit Vipers, are placed in the Family Viperidae (Subfamily Crotalinae), along with Palm Vipers, Copperheads, Cottonmouths and similar species. Herpetologists consider them to be the most advanced of all snakes.

Confined to the Western Hemisphere, Rattlesnakes reach their greatest diversity in the American Southwest and Mexico, with 13 of the 36 known species being found in Arizona alone. Only 4 species – the Eastern Diamondback, Eastern Massasauga, Pigmy and Timber Rattlesnake – range east of the Mississippi, while South America is home to but 2, the Neo-Tropical and Uracoan Rattlesnakes.

Beyond Sensing Heat

All Pit Vipers possess a sophisticated organ that detects the infra-red rays (heat) produced by birds and mammals. Located in a pit between the eye and nostril, it is far more refined than the receptors of boas and pythons.

The arrangement of heat receptors within the sensory organs are recreated in the brain and integrated with visual information received there. The pits may thus be considered more “imaging devices” than mere heat receptors, and provide detailed information concerning the size and location of warm-blooded animals. Aided by these unique organs, Rattlesnakes are able to hunt in complete darkness.

The Rattle

The rattle, unique among snakes, is composed of a series of loosely-connected segments. Specialized muscles in the tail vibrate the rattle to produce its characteristic sound.

A new segment is added at each shed. The number of rattle segments is not indicative of age, as old segments regularly break off and snakes may shed from 0-4 times yearly. The Santa Catalina Rattlesnake, confined to the island of the same name, is the only species that lacks a rattle. A number of non-venomous snakes vibrate their tails among dead leaves when disturbed, perhaps in imitation of Rattlesnakes.

Fangs

Vipers have evolved long, hinged fangs that fold back against the roof of the mouth when not in use. Venom is injected with a single bite, in the manner of a hypodermic needle.

The snake then retires and allows the prey to run off, following its scent trail once the stricken animal has expired. This strategy spares Vipers the injuries that can be inflicted upon snakes that must hold on while injecting venom (i.e. Cobras).

Parental Care?

All Rattlesnakes bear live young and some provide a degree of parental care, with females protecting their offspring until at least their first shed (9-14 days after birth). The Black-Tailed Rattlesnake has been shown to recognize siblings after a 2 year separation.

Further Reading

If possible, please visit the extensive Rattlesnake collection at the Staten Island Zoo.

A list of all known Pit Vipers and their ranges is posted here.

You can see and hear a Rattlesnake’s rattle in action here.