A Species In Decline
Gopher tortoise burrows are used by many forms of wildlife. Each year critical tortoise habitat is lost as more and more upland areas are developed. As tortoise habitat disappears so do many tortoise “burrow commensals” (other animals that depend on tortoise burrows for shelter and survival).
One of these species is a large, handsome snake known in story and legend throughout the Southeast — the eastern diamondback rattlesnake (Crotalus adamanteus).
The diamondback, along with many other upland snake species, is declining over most of its range. This page was developed to provide information about the decline of this magnificent creature and what can be done to help conserve the diamondback, the gopher tortoise and other upland species.
The ancestors of the eastern diamondback rattlesnake were part of an ancient dry-habitat fauna that stretched from Florida to the southwestern United States. This fauna included such forms as the scrub jay, gopher tortoise and burrowing owl – species familiar to modern Floridians. Rattlesnakes, which are in the Viper family of snakes (Viperidae), probably originated in Mexico and the Southwest about 8 million years ago. They have since spread throughout most of the continental U.S., parts of Canada, and Central and South America. In Florida, fossil remains indicate that the diamondback has existed in the area for at least 2 million years.
The eastern diamondback is the largest rattlesnake in the world. Although outlandish stories exaggerating the size of this snake are often told, here are the facts: adults are 4-5 feet in length. Large snakes are 6 feet long with a maximum length probably under 8 feet. Newborn snakes are 12-15 inches long. An average adult diamondback weighs 4-5 pounds. A real giant may tip the scales at 10 pounds or more.
Distribution & Habitat
The eastern diamondback ranges along the coastal lowlands from southeastern North Carolina to eastern Louisiana, including all of Florida and the Keys. Until the 1970s, the diamondback was common throughout much of its range; today it is only occasionally encountered. In some parts of its range it may be endangered or even extirpated. Although the diamondback is found in most natural communities of the southeastern Coastal Plain, it is most often thought of as an inhabitant of xeric (dry) uplands such as sandhills, clayhills and scrub. However, it will also make occasional forays into swamps and marshes, especially when water levels are low. Diamondbacks have been seen miles out at sea, apparently attempting to swim between islands. During the winter, diamondbacks take refuge in gopher tortoise and armadillo burrows, stump holes, root channels, under palmetto thickets and other underground cavities.
Eastern diamondbacks give live birth to about 14 young between July and October. Females may not breed every year. A rattlesnake, if unmolested, may live to the ripe old age of 20 years. The eastern diamondback feeds on a variety of small mammals and some birds. The bulk of its prey consists of rabbits and cotton rats. Diamondbacks hunt from a tight coil, remaining motionless, waiting to ambush prey that come within striking distance. They may spend from one day, to as much as a week coiled in the same position. Eastern diamondbacks have large home ranges that may encompass as much as 500 acres. The home range of females is usually smaller than that of males. Males may move long distances during the late summer, presumably in search of females. Eastern diamondbacks are primarily terrestrial (living on the surface of the ground), rarely climbing into trees and infrequently going underground during the summer. During winter, movements decrease; rattlesnakes in the northern part of the range often stay below ground, but those further south still remain on the surface much of the time.
Rattles probably evolved as a warning device to protect the snake from being accidentally crushed by large, hoofed mammals. The rattle is composed of hollow, interlocking segments that click against each other when the tail is vibrated. Rattlesnakes gain a new segment to the rattle every time they shed their skin. Since they may shed from one to three times per year, one cannot accurately estimate the age of the snake simply by counting segments. Segments also break off as the snake grows older.
Fangs and Venom
Like all vipers, rattlesnakes have a pair of long, movable hypodermic, needle-like fangs that fold against the roof of the mouth when not in use. These fangs are connected to venom glands on each side of the rattlesnake’s head. Rattlesnake heads are large to accommodate these venom glands. During a strike, venom is pumped by muscles surrounding the venom glands, through the fangs into prey. Rattlesnakes are also known as pit-vipers and possess two heat-sensitive pits on either side of their face. These pits are sense organs and detect radiant heat, and aid rattlesnakes in locating prey and increase striking accuracy. These pits are extremely sensitive and can distinguish differences in temperature of less than 0.2 C. These advanced systems evolved in pit-vipers as a means of obtaining food. It is the most advanced system that snakes have for capturing prey, and reduces the chances of injury to the snake. The venom of rattlesnakes is actually a digestive enzyme and is a complex mixture of proteins. The primary purpose of venom is to kill and digest prey. Venom is used in defense only as a last resort. Some venoms attack the nervous system (neurotoxic) while others attack the blood and tissue (hemotoxic). The eastern diamondback, like most rattlesnakes, has a combination of both types, but unlike most vipers, it has more neurotoxic properties. Although the diamondback’s real threat to public safety is very low (many more people are killed every year by lightning strikes, bee stings and domestic dogs), the perceived threat by the public is still quite high. Many biologists who have studied this species have found themselves in a position in which a rattlesnake had ample opportunity to strike in self-defense. Those few who have been bitten were usually handling the snake when the bite occurred.
Threats to Survival
Most experienced herpetologists feel that the eastern diamondback rattlesnake is declining. What threats face the diamondback? Habitat destruction is the greatest problem; no animal can survive without the proper habitat to support it. The second greatest threat is habitat fragmentation; as the landscape is broken up by roads, development and agriculture, the rattlesnake is brought increasingly into contact with humans. Intentional killing by humans occurs throughout the Southeast. In fact, some misguided people consider it their duty to kill any snake they see. Additionally, automobiles take their toll. The rattlesnake skin trade, which produces hides and curios, takes thousands of eastern Diamondbacks every year with no limit placed on the annual harvest. Although rattlesnake round-ups are not as numerous as they once were, they too contribute to the unregulated harvest; and have greatly impacted the diamondback and many other species of wildlife for many generations. Also, the treatment that snakes receive at these popular tourist events is not conducive to a conservation ethic and respect for our natural heritage. Is unrestricted exploitation the view of nature we wish to teach our children?
Public education is critical to the conservation of the diamondback. Protection of the snake from malicious killing, and the regulation of rattlesnake harvests are needed. Rattlesnake roundups can convert their activities to more wildlife-friendly festivals; and eliminate the mass killing of diamondbacks, and the negative impact such roundups have on the environment in general. Ecological research should continue so that we can learn more about the management needs of rattlesnakes in the wild. Strategically placed wildlife crossings on highways can benefit many species, especially the slow-moving diamondback. We should encourage investigations into the professional propagation of captive eastern diamondbacks, especially in semi-wild conditions. The captive breeding of this species for the pet trade, skins and curios may take pressure off wild populations. It would indeed be a tragic turn of events if this once common, magnificent reptile, which figures prominently in legend and literature, should disappear from our landscape.
Rattlesnake Conservation Committee
The Gopher Tortoise Council formed the Rattlesnake Conservation Committee in 1993. This committee has evolved into the Upland Snake Conservation Initiative. The purpose of this committee is to investigate the biological status of the eastern diamondback rattlesnake and promote its conservation. The committee works within the Gopher Tortoise Council to educate the public about the plight of this declining species. This page was produced to fulfill a portion of these goals.
Text by Karl Studenroth