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Living Sanibel: Eastern diamondback and pigmy rattlesnake

By Staff | Apr 19, 2017

Rattlesnake up close. KENNY KRYSKO

Eastern diamondback rattlesnake

(Crotalus adamanteus) VENOMOUS!

The largest rattlesnake in the world, this venomous pit viper is still common throughout Southwest Florida. Once found in Louisiana, Mississippi, Alabama, Florida, Georgia, and South and North Carolina, this snake has been relentlessly persecuted and hunted to extirpation throughout much of its historical range. Today it is reduced to remnant populations in southern Georgia, most of Florida, and parts of southern Alabama.

One reason for the decline of the diamondback throughout the Southeast is development. The rattlesnake prefers upland habitats such as longleaf and slash pine forests. These same habitats are coveted by developers since their dry, sandy soils can readily be turned into strip malls and subdivisions. As a result, the eastern diamondback rattlesnake is fast approaching threatened status because of the continued encroachment on its range.

Another cause of the snake’s declining numbers is the popularity of commercial rattlesnake roundups in which patches of saw palmetto are burned to drive the rattlers out from their cover so they can be killed. Another method used in these roundups is to pour gasoline into gopher tortoise burrows (a popular den for diamondbacks and indigo snakes) killing the tortoises and dozens of other species that frequent these excavations. After such a roundup, the rattlesnakes are eaten and the hides sold for the production of snakeskin purses and boots. In a paper published in 2008 by the American Society of Ichthyologists and Herpetologists, thousands of scientists united in strongly opposing these cruel and environmentally harmful roundups. Florida banned these destructive round ups years ago, but the practice is still common in Georgia and Texas.

Dusky Pygmy rattlesnake. KENNY KRYSKO

Another disturbing by-product of roundups affects natural selection. The eastern diamondback has large, loud rattles located at the end of its tail that it uses to warn potential predators when they get within 18 to 25 feet of the animal. Rattlesnake hunters use this behavior to locate the snakes they kill. Over time only the snakes that do not rattle or have little to no rattle survive. This results in a form of unintentional selective breeding, allowing the silent snakes to survive and pass on that genetic tendency, leading to a population with no means of warning its predators (or humans) of an impending attack.

The eastern diamondback rattlesnake is a lethal adversary, and any encounter with one of these large snakes in the wild should be taken seriously. A mature snake has up to one-inch fangs that can readily penetrate clothing, shoes, and leather boots. A lethal dose of the venom has been estimated at between 100-150 mg (i.e. less than an aspirin); an adult snake averages three to five times that amount (400-850 mg). The bite is extremely painful and highly necrotizing. Untreated, death can occur within hours.

On average, 7 to 12 people a year die in the United States from snakebites, as opposed to 100 deaths recorded annually from lightning strikes. The last recorded fatal rattlesnake bite in Florida occurred in Putnam County, Florida, in 2005 when Joe Guidry, 54, reached under his neighbor’s shed for a snake he thought he had shot and killed only to have it bite him in the hand, hitting a vein and killing him within seconds. Fortunately, unlike the grim situation with eastern coral snake anti-venom, there is ample pit-viper anti-venom available throughout the country.

The rattlesnake plays a vital role in the balance of any given ecosystem. It keeps rodent populations in check, feeding primarily on marsh rabbits, cottontails, squirrels, and rice rats. It also eats bobwhites and large insects. Aside from opossums, which are immune to their venom, the diamondback has few natural predators, for obvious reasons.

Dusky pigmy rattlesnake

(Sistrurus miliarius barbouri) VENOMOUS!

The smallest venomous snake found in Florida, the pigmy rattlesnake’s bite is seldom fatal. The record length for this diminutive rattler is a mere 30 inches, more than a foot shorter than the average length of a mature coral snake. Because of its size, this pit viper delivers roughly 18 mg of venom, which, while extremely painful to the victim, is only a tenth of the amount delivered by an eastern diamondback rattlesnake. A handful of people have lost digits to these bites, but deaths are extremely rare. The same readily available anti-venom serum used for the eastern diamondback is used to treat pigmy rattler bites.

The pigmy rattlesnake is carnivorous, foraging primarily on green and brown anoles, cotton mice, and insects. It tends to strike its prey quickly, then withdraw and wait out the effects of its toxin. While most small rodents succumb quickly, some reptiles can escape, only to die 10 to 15 minutes later. This small pit viper is a fairly common sighting at Myakka River State Park, especially along the road in the fall when the first cold snaps leave the snake seeking the warmth of the pavement.

Because it is so small, the pigmy is taken by a host of predators, including kingsnakes, opossums, great blue herons, and owls.

This is an excerpt from The Living Gulf Coast – A Nature Guide to Southwest Florida by Charles Sobczak. The book is available at all the Island bookstores, Baileys, Jerry’s and your favorite online sites.