Rattlesnakes on Our Barrier Islands; Part 8 – Eastern Diamondback Rattlesnake

This species is the one that causes the most concern for folks and enhances their fear of all snakes. The eastern diamondback rattlesnake (EDB) (Crotalus adamanteus) is the largest venomous snake in the U.S.  Most today will only reach a length 5 feet but there are records of this snake reaching 8 feet.  They can weigh up to 25 pounds, their head can be the size of a man’s fist, rattles can be the size of a human index finger, and they can carry over 1000 milligrams (mg) of venom, injecting as much as 300 mg in a single bite.  Though there are venomous snakes in the U.S. with a more potent venom, because of its size and the amount of venom they can inject, EDBs are considered by many to be the deadliest snake in our country.

They will lie quiet for long periods of time hoping prey approaches.  However, they are quick to respond to potential threats with their heart stopping rattle, can be heard from 20-30 feet away.  Their strike range is longer than most native snakes – reaching 2/3 of their body length (over 3 feet for a 5-foot snake) – and are considered very dangerous.  The venom is a cocktail of hemotoxins, and neurotoxins and bites left untreated can result in death in less than 24 hours.  All that said – only about 1-2 people die each year from this snake.  Statistics show that most are bites on the hands of men.  Most were intentionally interacting with the snake.  95% were either trying to catch or kill them.

EDBs only exist in the lower coastal plains of the southeastern U.S.  They are found throughout Florida and are the only rattlesnake I am aware of that lives on our barrier islands.  They prefer high dry ground in pine flatwoods, scrub, pine forest, sand hills, around wetlands, grassy forest edges, palmettos, and are usually near water.  They need burrows to avoid heat and cold and are often found in gopher tortoise burrows and holes around tree stumps.  They are good swimmers and have no problem crossing salt water to reach our barrier islands.

They are primarily diurnal in activity but will aestivate in holes, burrows, and dens during the hot months of summer.  Adults feed primarily on rabbits but will take rodents when available.  The young focus on smaller rodents but could take birds, or other small mammals.  Though full grown rattlesnakes have few predators, they are not considered an apex predator.  Numerous creatures feed on the young and subadults, such as – alligators, feral hogs, bobcats, hawks, eagles, owls, wading birds, snake eating snakes (such as black racers, cottonmouths, king snakes, and indigos).  King snakes are immune to their venom.  Deer may trample a rattling young snake, but the #1 predator are humans – and not for food.

Breeding occurs in the spring with birth coming in late summer/early fall.  Most snakes lay eggs but rattlesnakes, and other vipers like cottonmouths, keep the eggs within the mother giving live birth.  EDBs can give birth to as many as a dozen offspring.  Young rattlesnakes may not yet have a rattle, but they do have venom, and it is just as toxic as the adults.

EDB populations have declined across their range – they may no longer exist in the state of Louisiana.  The cause of decline is most certainly humans.  Development of habitats into farms and neighborhoods force EDBs into new territories where competition impacts the population, or into human landscapes where they will surely be killed.  There are still folks who go into their natural habitats to kill or collect them for local events.  They are a species of concern in most states, including Florida.