Timber Rattlesnake Crotalus horridus - Endangered

Adult Male from Brown County
Adult Female from Brown County

Identification: Adult timber rattlesnakes are among the most distinctive snakes in Indiana as they are incredibly large and heavy-bodied with strongly keeled scales and a segmented keratinous rattle at the tip of the tail. Contrary to popular belief, the snakes are hesitant to use this rattle and prefer to remain hidden, when possible. In fact, snakes typically only rattle at people if they are moving over open ground when approached or are physically touched. Importantly, many other snakes will vibrate their tails when threatened, thus making an audible rattle sound. Hearing a snake rattle its tail is not sufficient to identify it as a rattlesnake, though seeing the physical rattle is. Juvenile rattlesnakes may have only a single "button" on their tail tip and are incapable of making a sound, but adults may have long, tapered rattles of 15 segments or more. Though a rattlesnake's rattle length is indicative of age, most older snakes have broken rattles. Rattlesnakes are otherwise unique in that their coloration transitions from very light near the head and neck, and darkens posteriorly, ending in a velvety black tail. Though many snakes are brown or gray in color, bright yellow-gold rattlesnakes are common in Indiana. Black chevrons run from the neck down the back with a light orange-brown vertebral stripe down the middle. Timber rattlesnakes are not the longest snake in the state, but they are, undoubtedly, the heaviest as large males are often more robust than a man's forearm. Adult females are typically two to three feet (60 - 90 cm) in length, but adult males commonly exceed four feet (1,2 m) with some individuals growing to nearly five feet (1.5 m) in length.

Similar Species: Adult timber rattlesnakes are so heavy bodied and distinctive, that they are difficult to mistake for any other native species. hog-nosed snakes are perhaps the most similar species in Indiana as they are also robust for their size and exhibit a similar range of color variants (dark gray-brown to yellow-orange). However, hog-nosed snakes have a blotched dorsal pattern, instead of a chevron pattern, have a distinctly upturned snout, and lack a rattle. Juvenile rattlesnakes are light gray in color and are similar to juvenile copperheads, but have chevrons instead of hour-glass bands and have a small button at the tip of the tail, where copperheads have a light yellow-green tail tip.

All four of Indiana's venomous snakes have thick bodies, broad chunky heads, elliptical pupils, heat sensitive pits between the eyes and nostrils, and undivided post-anal ventral scales (under the tail). However, most of these characteristics require close examination, elliptical pupils can dilate and become round, and many non-venomous snakes (especially hog-nosed snakes) will broaden and flatten their heads in self defense. Therefore, it is always best to treat any snake that you cannot positively identify as potentially venomous. Venomous snakes are best left alone as most snake bites occur when someone attempts to handle or kill the snake. Snakes are not aggressive and do not hunt, attack, or chase people when left unmolested.

Distribution: Once found throughout much of southern Indiana, timber rattlesnakes are now restricted, predominantly, to the rugged forests of Brown County and portions of adjacent Morgan and Monroe Counties. A small population also remains in Jackson and Washington Counties and snakes are periodically reported from Perry County, though the status of these remnant populations is largely unknown. Timber rattlesnakes are large, slow-moving snakes and males may range across more than 200 acres (100 hectares) during the breeding season. As such, they are highly susceptible to road mortality and have also been the victim of targeted persecution for many years. A combination of direct persecution and habitat loss/fragmentation are to blame for the dramatic decline of this iconic snake in Indiana. They are now protected in Indiana, as a state endangered species.

Un-glaciated Forest in Brown County
Mesic Forest in Brown County

Distribution Map
Distribution map of Timber Rattlesnake (Crotalus horridus)
Photographs