Timber Rattlesnake

Crotalus horridus
Monday, July 23, 2012

             This rattlesnake is the only species of venomous snake at Mountain Lake. It is unmistakably different from any other snake in this area, largely because of its massive girth. While not the longest snakes at MLBS, reaching 189 cm (6’ 2”) in length, they have very thick and heavy bodies. One of the most distinguishing features of all venomous snakes (except for coral snakes) is their narrow neck and rather wide head. Also, vertical, slit-like pupils are a trait only present in venomous snakes in the US.

             The timber rattlesnake can be found in several common color variations, each very different in appearance. The only morph present in this area is the yellow color variation, marked by a black or dark brown pattern of 20-29 irregularly V-shaped crossbands across a yellow or brown body. 

             Timber rattlesnakes hibernate in dens located in rocky crevices or southward-facing outcroppings. These dens typically extend below the frost line, and they may share them with up to 60 other rattlesnakes and with other species such as copperheads, black rat snakes, or garter snakes. In the early spring and late fall, as well as in warm days during the winter, they spend a great deal of time sunning themselves on rocks near to their hibernaculum. However, as the weather becomes warmer, they begin to migrate away from their den. Although they return to their same den every year, they often travel 2-4 kilometers as solitary hunters during the summer months. 

             Small mammals (mainly mice, rats, squirrels, and rabbits) make up around 90% of rattlesnakes’ diets, while the rest consists of small birds, other reptiles, and amphibians. Rattlesnakes, like other pit vipers, sometimes develop an appetite for a certain type of prey and will specialize on it to the exclusion of all else, while others have a varied diet. Although rattlesnakes do not possess hearing organs, they make up for it with a precise vibration sensor located in the lower jaw and connecting skull bones. This allows them to precisely detect the size of potential prey items. They can also detect their prey using the heat-sensitive pits (often mistaken for nostrils) in their head between their nostrils and eyes. These are sensitive to even very slight changes in radiant heat and enable the rattlesnake to literally see in the infrared spectrum. This “sixth sense” allows snakes to find and kill prey very accurately, even in the pitch dark. Experiments have proven that, even deprived of their senses of sight and smell, some pit vipers are able to accurately strike at moving objects that are less than 2° C warmer than the ambient background. 

             Timber rattlesnakes are often nocturnal hunters, laying in wait with their dappled bodies camouflaged under rocks or behind logs. When a prey item of suitable size passes by, the snake will immediately strike out with its fangs, injecting lethal venom into the prey. The snake then releases its prey, and, after waiting for some time, follows its scent trail and consumes the now dead prey whole.

             After mating in midsummer, female rattlesnakes store sperm in their bodies all throughout the winter before fertilizing their eggs in the spring. Timber rattlesnakes are ovoviviparous, meaning that the eggs are incubated and hatched inside the female and she gives birth to 6-10 live and independent young in August-October. The young, around 33 cm (13”) long at birth, begin shedding their skin when they are only around 1 week old. From then on, every shedding (usually every 1-2 years) reveals a new “button” on the end of the rattle. However, as these rattles tend to break off, this is not an accurate measurement of age. While males become sexually mature in 4-6 years, females are not able to bear young until they are 7-13 years old. These snakes can live for up to 30 years in the wild.

             This snake was discovered on the road near the Walton Pavilion and was caught by Eric Nagy.  It is a female.

Hazel Galloway

 
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