Eastern vs Western Diamondback Rattlesnake: Key Differences

Key differences at a glance

The eastern diamondback rattlesnake (Crotalus adamanteus) and the western diamondback rattlesnake (Crotalus atrox) are two separate species of pit viper in the genus Crotalus. They share the classic chain of diamond-shaped blotches on the back, which is why both are called diamondbacks, but they differ in range, pattern details, size, habitat and population trend.

In short, the eastern diamondback is the bigger, heavier snake of southeastern pine forests, with crisp, bright-edged diamonds. The western diamondback is the dusty, more variable snake of deserts and grasslands, with a ringed black-and-white tail. Their ranges never meet.

Range: Southeast vs Southwest

The eastern diamondback is found only on the coastal plain of the southeastern United States. Its range runs from southeastern North Carolina through South Carolina, Georgia and all of Florida to the Keys, and west along the Gulf Coast through southern Alabama and Mississippi to southeastern Louisiana, where it has probably disappeared.

The western diamondback has a much larger range. In the United States it occurs in central and western Arkansas, Oklahoma, most of Texas, southern New Mexico and Arizona, extreme southern Nevada and southeastern California. In Mexico it ranges across much of the north and south along the Gulf side as far as Veracruz, with isolated populations farther south.

Between the two lies a broad gap across Louisiana and eastern Texas where neither species lives. If you see a diamondback in Florida or Georgia, it is an eastern; if you see one in Texas or Arizona, it is a western. Regional guides such as snakes in Florida and snakes in Arizona cover the other snakes you may meet.

Pattern, color and tail bands

Both species have a row of roughly two dozen or more dark diamonds along the back, but they look different up close.

• Eastern diamondback. The background is brown, olive or grayish. Each dark brown to black diamond has a lighter center and is outlined by a clean row of cream or yellow scales, so the pattern looks sharp and high-contrast. Toward the tail the diamonds turn into crossbands, and the tail has 5–10 dark bands without bright white rings.
• Western diamondback. The background is usually tan, gray, pinkish or brick-red, matching local soils. The diamonds are brown and often look dusty or speckled, with pale borders that are less crisp. The tail has bold black and white rings of roughly equal width, which gives it the nickname “coon tail.”

Both have pale stripes on the face running from the eye toward the mouth. In the western diamondback, watch for look-alikes: the Mojave rattlesnake also has a ringed tail, but its black rings are narrower than its white ones.

Size: which diamondback is bigger?

The eastern diamondback is the bigger snake, and in fact the largest rattlesnake of all. Most eastern adults are 0.9–1.8 m (3–6 ft) long and weigh about 2–5 kg (4.4–11 lb). Snakes over 2.1 m (7 ft) are rare but documented, and 2.4 m (8 ft) snakes have been reported but not verified.

The western diamondback is the second-largest rattlesnake. Adults are commonly about 1.2 m (4 ft) long, specimens over 1.5 m (5 ft) are uncommon, and the largest reliable length is about 2.1 m (7 ft). Medium-sized westerns weigh about 1.2–2.7 kg (3–6 lb), and very large ones are reported at up to 6.7 kg (15 lb). In both species, males grow larger than females. For more detail, see how big an eastern diamondback gets.

Habitat and behavior

Eastern diamondbacks are tied to the longleaf pine ecosystem: open, fire-maintained pine savanna, flatwoods, sandhills, coastal scrub and the edges of wetlands. They rely heavily on gopher tortoise burrows for shelter from heat, cold and fire, and are good swimmers that cross to barrier islands.

Western diamondbacks are much more adaptable. They live from below sea level up to about 2,000 m (6,500 ft), in deserts, creosote flats, mesquite grassland, rocky canyons and pine-oak woodland. They shelter in rodent burrows and rock crevices, and in winter some gather in communal dens, sometimes with other snake species. Westerns also cope better with semi-urban land and are regularly found on the edges of cities such as Phoenix and Tucson.

Both species are ambush hunters that eat mainly mammals. Eastern diamondbacks specialize on rabbits and rats, while westerns eat a wide range of rodents such as kangaroo rats, woodrats, pocket gophers and ground squirrels, plus birds and lizards. Both give birth to live young, usually about a dozen per litter.

Which is more dangerous?

Both snakes are dangerous, and any bite is a medical emergency. The eastern diamondback is often called the most dangerous snake in North America because it is so large, with the longest fangs of any rattlesnake for its length and an average venom yield of about 400–450 mg. The western diamondback’s venom is weaker drop for drop, but it can still inject a large amount, averaging about 250–350 mg.

In practice, the western diamondback causes more bites in total, because it is common across a huge and populated region, and it is thought to be responsible for most rattlesnake bites in the United States and many in northern Mexico. Neither species is aggressive; bites mostly happen when people step on, handle or try to kill a snake. Keep a safe distance and, if someone is bitten, call 911 and seek emergency medical help immediately.

Populations and conservation status

Both species are listed as Least Concern on the IUCN Red List, but their trends differ. The western diamondback has a stable population and remains common over most of its range.

The eastern diamondback is decreasing. It has lost most of its longleaf pine habitat, is protected as endangered in North Carolina, has probably vanished from Louisiana, and has been petitioned for listing under the US Endangered Species Act. Rattlesnake roundups have affected both species; in the West, events in Texas still collect large numbers of western diamondbacks each year.

Can they interbreed?

Because their ranges are separated by hundreds of kilometers, eastern and western diamondbacks do not meet in the wild, and natural hybrids are not known. They are treated as distinct species, each adapted to its own landscape: fire-maintained pine forest in the East and arid scrub and grassland in the West.