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Timber Rattlesnake

Facts about the Timber Rattlesnake from the printable Fact Sheet  

Species Description

Note: A variety of the Timber Rattlesnake, called the Canebrake, occurs in lower elevation coastal plains and is, on average, slightly larger than the upland form that occurs in the Appalachian Mountains and northeastern United States. It utilizes different foraging habitats, can overwinter in a greater variety of places, can look strikingly different, and behaves differently. Canebrakes are fairly common throughout their range and, while technically the same species; Canebrakes have gone back and forth between being a valid subspecies. At the moment no subspecies are recognized but such a designation would allow for a legal framework to effectively protect the more rare upland snakes separately from Canebrakes where both forms occur. This page discusses the identification, life history, and conservation concerns of the upland and northern form of the Timber Rattlesnake, not the Canebrake.

The physical coloration of the Timber Rattlesnake is quite variable throughout the species' range however the basic pattern, dark W-shaped bands across the body on a lighter background, is fairly consistent. The background color varies from yellow to brown to gray and gets darker closer to the tail. The tail itself is usually black and some individuals are almost entirely that color. In more northern populations individuals tend to be darker and are most often yellow or black. The W-shaped bands are usually outlined in a lighter color that can even be seen on the darkest of individuals. Sometimes a light brown line along the spine runs the length of the body though that is a trait more common in the Canebrake. Neonates have the same pattern as adults but usually have a gray body color for the first year after being born.

Timber Rattlesnakes are a large and robust snake, with males typically reaching lengths of up to 1.32 meters (4 feet 3.97 inches) and females up to 1.09 meters (3 feet 6.91 inches). While stories are often told of Timber Rattlesnakes exceeding two meters in length these stories are exaggerated and it is unlikely that any individuals exceed 1.5 meters (4 feet 11 inches). Hatchlings are generally about 28 cm (11.02 inches) in total length.

Timber Rattlesnakes have very heavily-keeled scales, a divided anal plate with a single row of ventral scales behind the vent. The rattle, which is held upright when the snakes feel threatened, is a very good way to distinguish the rattlesnakes from certain non-venomous species that can have somewhat similar patterns such as a watersnake or milksnake.

Conservation Concerns

As a long-lived species with a high age at maturity and low annual fecundity, survival of adults, especially females, is key to population viability. Habitat fragmentation by roads has resulted in many snakes being killed by traffic, often intentionally. Because older and larger snakes tend to disperse farther from the dens every year it is those larger individuals, who are most important to rattlesnake populations, that are most likely to encounter roads. In some areas Timber Rattlesnake dens have been isolated entirely from larger populations by roads, fields and developments that they have begun to differentiate genetically.

Persecution by humans is a major threat to the species and until the 1970s, many northeastern states paid a bounty for any killed rattlesnake. In most of these states the species is now protected but because bounty hunters were able to find gestating females more easily than any other snakes and because large numbers of snakes could be harvested at dens, the bounty effectively reduced populations to low levels in many places and possibly wiped out denning colonies. Despite the legal protections afforded to the species in the northeast now, intentional killing of snakes is still a common practice. In the southeast, while no bounty is paid for the killing of Timber Rattlesnakes, the species is not protected and killing of the species is legal.

While bites from Timber Rattlesnakes can harm people, such bites are extremely rare and usually are the result of a person harassing or attempting to kill the snake. When a Timber Rattlesnake is encountered in the wild the safest thing to do is to leave it alone and walk around it. The snake will not defend itself unless provoked. In the event of a bite one should remain calm and seek emergency help. Deaths from Timber Rattlesnake bites are almost unheard of and if medical help is sought out quickly it is possible to avoid permanent tissue damage. If a Timber Rattlesnake is seen on your property and you feel uncomfortable having it in close proximity to your house, rather than kill it you should contact your state department of natural resources or fish and wildlife. Many states have removal programs and people in those departments should know who the best person to contact is.

Taxonomy

The species was described by Linnaeus in 1758 and currently no subspecies are recognized. The genus, Crotalus, literally means "hollow in the rocks", after the denning habitat that this species uses. Horridus could mean "horrible", however another meaning of the word in latin is "bristly" which could refer the snake's extremely rough texture.

Distribution

Timber Rattlesnakes are found primarily in temperate forests throughout the eastern United States. They range from northern Florida to eastern Texas north to Wisconsin and New Hampshire but are absent from Michigan. Historically their range included southeastern Ontario and southern Maine but populations there are believed to have been extirpated.

While the coastal canebrake form of the Timber Rattlesnake can be quite common in the southeastern United States, Timber Rattlesnakes are generally considered uncommon or rare through most of the species range. Even in the southeast where canebrakes occur, the upland Piedmont snakes are much more rare and are broken into smaller fragmented populations.

Habitat

Populations of Timber Rattlesnakes throughout the Appalachian Mountains and connecting ranges to the northeast can only persist where suitable denning habitat is available. Denning areas are typically rocky and are either made up of crevices at the bottom or cliffs or talus slopes below cliffs. In most places den sites are situated on south or west-facing slopes where temperatures tend to be higher. Gravid females require exposed rocky areas where they can maintain body temperatures of about 26.4°C (79.52°F) 24 hours a day during reproductive years. Gestation sites are usually at the dens themselves or within 500 meters (1,640 feet)of the den along the top of a ridgeline.

Timber Rattlesnakes exhibit very high rates of den fidelity; colonization of new denning areas is extremely rare and may now also be encumbered by habitat fragmentation with roads, fields, agricultural fields, and development.

Foraging habitat is made up of dry deciduous forests, often with rugged terrain. Forest composition can vary but mast-producing species of tree such as oak, beech, and hickory are important as they provide food for the prey of Timber Rattlesnakes.

Movement and Home Range

Home ranges and movement vary greatly among Timber Rattlesnakes depending on sex, age, and reproductive state. Timber Rattlesnakes leave denning areas in mid-April in southern parts of its range and mid-May at the more northern extremes. Male Timber Rattlesnakes have home ranges of about 90 ha (222.4 acres), non-gestating females about 30 ha (74.12 acres), and gestating females roughly 8.5 ha (21 acres). Males and non-gestating females move between 1.6 to 4 km (0.994-2.485 miles) from the dens each year, with larger individuals and males moving greater distances. Except gravid females, snakes typically move along a non-overlapping route and complete a loop ending back at the den at the end of the foraging season.

Gestating females move to birthing sites either at the dens or on top of the ridges near to them and will remain under and near chosen features, commonly referred to as birthing rocks, through the summer until birthing occurs some time in August to September. One to two weeks after birthing, when her young have shed their skins, females will leave their birthing sites to forage before returning to dens and overwintering. After their first shed, neonates exhibit sporadic bursts of movement but appear to follow the scent trails of conspecific snakes to locate the den they will return to every following year.

Diet

Timber Rattlesnakes have specialized heat-sensing pits on the front of their heads that allow them to find warm-blooded prey such as mammals. Rodents including mice, chipmunks, and voles make up a major portion of the Timber Rattlesnake's diet. Occasionally other food items are taken such as amphibians and birds. Prey is injected with a venom made up of both hemotoxins and neurotoxins that immobilize animals and begins to digest them from within. During envenomation snakes imprint on the smell of their targets and use that, as well as the scent of their own venom, to locate their deceased prey.

Reproduction

Timber Rattlesnakes are a late-maturing species with males reaching sexual maturity between 4 and 6 years of age and females at between 9 and 10 years in northern populations. As with other species of snake, reproductive maturity is influenced more by size than actual age with females becoming mature at about 91 cm (35.83 inches) in snout-vent length and weighing just over 600 grams (21.16 ounces). Because of short active periods and the high costs of reproduction, females reproduce every three to four years in northern populations with females occasionally reproducing every two years farther south. Between 4 and 14 young are usually produced by females during reproductive years with larger females being the most fecund.

Gestating females spend the summer at birthing sites either near the dens or on ridges above them where they can maintain a constant body temperature of about 26.4°C (79.52°F). Females will not eat during this time. After birthing, a female will stay with her young until they shed their skin for the first time at least a week later at which point she will head to foraging habitat to feed before returning to her den. Young will then follow pheromone trails of adults back to the den and may forage along the way. Timber Rattlesnakes can live to be about 25 years old though individuals have been observed up to 30.

Literature Cited

Adams, J.P. 2005 Home Range and Behavior of the Timber Rattlesnake (Crotalus horridus). Thesis, Marshall University, Huntington, West Virginia, USA.

Aldridge, R.D. And W.S. Brown. 1995 Male Reproductive Cycle, Age at Maturity, and Cost of Reproductionin the Timber Rattlesnake (Crotalus horridus). Journal of Herpetology 29(3):399-407.

Brown, W.S. "Biology, status, and management of the timber rattlesnake: a guide for conservation" Lawrence, Kansas: Society for the study of reptiles and amphibians. 1993

Brown, W.S. And F.M. MacLean. 1983. Conspecific scent-trailing by newborn timber rattlesnakes, Crotalus horridus. Herpetologica 39:40-43

Clark, R. W. 2002 Diet of The Timber Rattlesnake, Crotalus horridus. Journal of Herptology 36(3):494-499.

Clark, R.W., W.S. Brown, R. Stechert, and K.R. Zamudio. 2009 Roads, Interrupted Dispersal, and Genetic Diversity in Timber Rattlesnakes. Conservation Biology 24(4):1059-1069.

Furman, J. "Timber Rattlesnakes in Vermont & New York". University Press of New England: 2007

Gardner-Santana, L.C. and S.J. Beaupre. 2009 Timber Rattlesnakes (Crotalus horridus) Exhibit Elevated and Less Variable Body Temperatures during Pregnancy. Copeia 2:363-368.

Gibbons, J. W. 1972. Reproduction, growth, and sexual dimorphism in the canebrake rattlesnake (Crotalus horridus atricaudatus).Copeia 1972:222-226.

Martin, W.H. 1993 Reproduction of the Timber Rattlesnake (Crotalus horridus) in the Appalachian Mountains. Journal of Herpetolgoy 27(2):133-143.

Martin, W. H., D. J. Stevenson, and P. B. Spivey. "Timber Rattlesnake", in Jenson, J. B., C. D. Camp, W. Gibbons, and M. J. Elliot, editor, Amphibians and Reptiles of Georgia, 2008.

Reinert, H.K. And R.T. Zappalorti. 1988 Field Observation of the Association of Adult and Neonatal Timber Rattlesnakes, Crotalus horridus, with Possible Evidence for Conspecific Trailing. Copeia 4:1057-1059.



Timber Rattlesnake Conservation

Photographs of Timber Rattlesnakes

For thousands of years, Timber Rattlesnakes have lived and hunted in one of the oldest mountain ranges in the world, the Appalachians. They are one of the few remaining top predators surviving in the Appalachians and the greatest remaining icon for the wild places that still exist in Eastern North America. However, every year Appalachian Timber Rattlesnakes decline further as snakes are killed in backyards and on roads, and their distribution continues to shrink.

Timber Rattlesnakes are important; they are important as predators of small mammals and have played a prominent role in cultural and religious heritage of the Appalachian region. Just over 200 years ago the timber rattlesnake was used as an icon for our independence during the American Revolution occurring on flags with the saying "Don't Tread on Me."

Timber Rattlesnakes have already gone extinct in Maine and Rhode Island and only one population remains in New Hampshire. They are protected in many of the Appalachian states but their populations continue to decline. To prevent the disappearance of the last remaining iconic predator of our Eastern Forests, we need to act now.

The Orianne Society, in Partnership with the IUCN Viper Specialist Group, implemented a program to conserve Timber Rattlesnakes with the goals of preventing further declines and promoting the species recovery in the Appalachian Region. We have decided to initially focus in two areas: the Northern Appalachians where the Timber Rattlesnake is critically endangered, and in the Southern Appalachians where they are rare and declining rapidly but there is little to no protection of the species by local governments.

Projects The Orianne Society is currently implementing include:



Timber Rattlesnake Projects



Recovery of Timber Rattlesnakes in Vermont

Following years of direct persecution including the killing of rattlesnakes for paid bounties until the early 1980s, only two populations of Timber Rattlesnakes remain in the state. We are working with Vermont Fish and Wildlife, the Vermont Chapter of the Nature Conservancy, and the Vermont Herpetological Atlas to conserve and restore rattlesnakes in Vermont. We are currently working to update the recovery plan including required criteria for downlisting them to threatened at a state level. We are conducting field studies to determine the habitats snakes use with ultimate plans for protecting 100% of the area used by the remaining two populations. To meet the goal of having three populations in the state, we are trying to determine if there are additional populations that to date have gone unnoticed and planning for a potential reintroduction if another population is not discovered. We are also working with local communities to raise awareness on the importance of timber rattlesnakes in the region by giving annual seminars and sending packets to people living in proximity to existing rattlesnake populations. As part of the packet, local residents receive a refrigerator magnet with phone numbers for individuals (including Orianne employees) that are on-call, to come and relocate rattlesnakes that show up in people's yards.





Timber Rattlesnake Database

Our work to conserve Timber Rattlesnakes in the southern Appalachians occurs primarily in Georgia and North Carolina. Little research has occurred on this species in this area, however, we do know, mostly through anecdotal reports, that populations of Timber Rattlesnakes in the southern Appalachian mountains appear to be declining.

Our staff monitors Timber Rattlesnakes in the southern Appalachians and records data on where these species are found and what habitat they are using. We are using this information to populate a database of these occurrences. This information will allow us to monitor population trends and identify and mitigate local declines before they go too far and to identify critical habitat that the snakes need to survive.





Fire Ecology and Timber Rattlesnakes

Historically, wildfire was an important ecological process in the Appalachian Mountains. For many years fires have been suppressed, but recently prescribed fire is being used more frequently. We are conducting research to determine the importance of fire to the ecology of Timber Rattlesnakes. Specifically, we are determining how prescribed fire influences the availability of gestation sites, overwintering sites, and prey in the Southern Appalachian Mountains.