Eastern Diamondback Rattlesnake

About the eastern diamondback rattlesnake

The eastern diamondback rattlesnake is a species of pit viper in the family Viperidae, and no subspecies are currently recognized. It holds two records at once: it's the largest rattlesnake species alive, and it's one of the heaviest venomous snakes in the Americas, rivaled in bulk mainly by the much longer king cobra and the shorter, bulkier Gaboon viper. A specimen shot in 1946 measured 2.4 m (7.8 ft) and weighed 15.4 kg (34 lb), and maximum reported lengths run to 2.5 m (8.25 ft), though researchers have questioned those upper figures because voucher specimens are lacking. Snakes over 2.1 m (7 ft) are rare but well documented — one herpetologist offered a standing reward of $100, later $200, for a confirmed 2.4 m (8 ft) specimen for years and never had to pay it. A 2.2 m (7.3 ft) animal was caught outside a neighborhood in St. Augustine, Florida, in September 2009.

Most individuals are far smaller than the record-holders. Reported lengths run from about 0.8 to 1.8 m (2.75 to 6 ft), with one study of 74 snakes finding an average of 1.7 m (5.6 ft). Average body mass is roughly 2.3 kg (5.1 lb), and laboratory-kept specimens averaged 2.55 kg (5.6 lb), ranging from 0.8 to 4.9 kg (1.8 to 10.8 lb); a few large individuals can top 5.1 kg (11.3 lb) or even 6.7 kg (15 lb). Unusually for a rattlesnake, males typically grow larger than females, a rare case of reversed sexual size dimorphism.

The color pattern is the giveaway: a brownish, brownish-yellow, brownish-gray, or olive ground color overlaid with 24 to 35 dark brown to black diamond shapes, each edged in cream or yellow scales. Toward the tail the diamonds give way to crossbands, followed by 5 to 10 bands ringing the tail itself. The belly is yellowish or cream with dark mottling along the sides, and a dark stripe runs from behind each eye down to the corner of the mouth, bordered above and below by pale stripes. The rattle at the tip of the tail is made of hard, hollow, loosely connected segments that break off over time and are replaced with every shed. The species is endemic to the southeastern United States, found along the coastal plain from southeastern North Carolina through peninsular Florida to the Keys, and west along the Gulf Coast through southern Alabama and Mississippi into southeastern Louisiana.

Behavior and diet

Eastern diamondbacks shelter by tunneling into burrows dug by gophers and gopher tortoises, emerging in the morning or afternoon to bask; some research suggests they spend less time underground during their active season than once thought. They're largely terrestrial and not built for climbing, though individuals have occasionally been found in trees and bushes, apparently while hunting, with large snakes spotted as high as 10 m (33 ft) up. They're also strong swimmers, regularly seen crossing open water between barrier islands and the mainland off the Georgia coast, in the Gulf of Mexico, and in the Florida Keys, sometimes miles from land.

Temperament varies by individual. Some snakes allow a close approach while staying silent; others start rattling from 6 to 9 m (20 to 30 ft) away. When threatened, a diamondback raises the front third of its body into an S-shaped coil and can strike to at least a third of its own body length, in as little as a tenth of a second. Contrary to popular belief, it doesn't need to rattle before striking and is fully capable of a silent strike. Most snakes prefer to retreat toward cover, facing the threat as they back away, rather than press an attack.

The diet centers on small mammals, especially rabbits and rice rats, along with birds; recorded prey includes a king rail, a young wild turkey, and towhees and bobwhite quail. Adults can easily swallow a full-grown cottontail, and even juveniles take adult mice, so young snakes rarely bother with smaller prey like lizards. Eastern cottontails and marsh rabbits make up the bulk of the diet across much of Florida. A diamondback will strike and release large prey, then track it by scent as it dies, and it can lie coiled in ambush for up to a week waiting for something to pass. When prey is scarce, it will scavenge carrion. Reproduction follows the ovoviviparous pattern typical of rattlesnakes: gestation lasts six or seven months, and a female gives birth to between 4 and 28 young, usually between July and early October, with broods averaging about a dozen. Newborns measure 30-36 cm (12-14 in) and look like miniature adults except for a small button in place of a rattle. They stay near the mother for only 10 to 20 days before dispersing to hunt on their own, and because females breed only every two to four years, the species has a slow reproductive rhythm.

Range and habitat

The eastern diamondback rattlesnake is found only in the southeastern United States: from southeastern North Carolina south along the coastal plain through peninsular Florida to the Florida Keys, then west along the Gulf Coast through southern Alabama and Mississippi to southeastern Louisiana. Within that range it favors dry, sandy country — upland pine forest, pine and palmetto flatwoods, sandhills, coastal maritime hammocks, longleaf pine and turkey oak habitat, and xeric mixed woodlands — along with grass-sedge marshes, swamp forest, cypress swamps, and salt marshes, and it will use wet prairies during dry spells. A wiregrass ground layer, kept open by frequent burning, is an important feature of good habitat, and the snakes rely heavily on burrows dug by gophers and gopher tortoises for shelter in both summer and winter.

Conservation status

The eastern diamondback rattlesnake is classified as Least Concern (LC) on the IUCN Red List, a category reserved for species with a wide distribution or large presumed population that aren't declining fast enough to qualify as more threatened — but its population trend was already recorded as downward when last assessed in 2007. The species is likely extirpated from Louisiana, last seen there in 1995, and some scientists believe it may also be gone from North Carolina, where it hasn't been documented since the early 1990s and where state law protects it as endangered. The U.S. Fish and Wildlife Service is currently reviewing the species for federal listing, citing a recent decline that has left the current population at an estimated 3% of its historical size.

The main threats are habitat loss and fragmentation, to which the species adapts poorly because of its slow life history and limited dispersal, along with direct killing by humans and highway mortality. Rattlesnake roundups add pressure by removing snakes from the wild for exhibition, sometimes using the harmful practice of pouring gasoline into suspected burrows. A South Carolina study found that translocating snakes away from disturbed habitat produced positive results, offering one tool for conservation going forward.