Anti-predator Adaptations: cryptic
While timber rattlesnakes are not aggressive and vicious, their venom is extremely strong. (Grzimek, 1975)
Like the other snakes in the family Viperidae, timber rattlers are pit vipers. This means they have heat sensitive pit organs located between the nostrils and the eyes. They are sensitive to radiant energy and can distinguish very slight changes in temperature.
Communication Channels: tactile ; chemical
Perception Channels: visual ; infrared/heat ; tactile ; vibrations ; chemical
Populations of timber snakes are rapidly being depleted across the species' range. The main causes are habitat destruction, snake hunting, and commercial collection for the pet trade. Several states have passed laws protecting the timber snake, but it is not on the threatened species list in many states. The species is not in serious danger but is headed in that direction unless efforts are made to protect it. (Brown, 1993)
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
The timber rattlesnake is venomous and can harm humans if they are bitten. However, they typically only bite in defense.
Negative Impacts: injures humans (venomous )
Timber rattlesnakes play an important part of many ecosystems by keeping the populations of small mammals in check.
Positive Impacts: controls pest population
Their main food source is small mammals, in particular mice, rats, squirrels, and rabbits. Birds are also sometimes killed. The prey is killed when bitten because the snake injects venom. Timber rattlesnakes wait until the animal is dead then swallows prey whole.
Animal Foods: birds; mammals
Primary Diet: carnivore (Eats terrestrial vertebrates)
Historically, this species was found in most of the eastern United States. It was known from New Hampshire south and west to Pennsylvania and New Jersey, throughout the Appalachians, all of southeast down to the panhandle of Florida, west to eastern Texas, Oklahoma, Kansas and extreme southeastern Nebraska. Populations have also been found along the Mississippi drainage as far north as Minnesota, and in the Ohio River valley throughout southern Illinois and Indiana and extreme southern Ohio. This is the historic extent of the range, but the species has been extirpated in many areas, and populations are patchy and fragmented.
Biogeographic Regions: nearctic (Native )
In the northern parts of their range, timber rattlesnakes live in forested rocky hills. In the southern parts of their range these snakes are found in uninhabited swampy areas. Crevices in rocky cliffs usually facing south or large boulders piled together make up the hibernating dens. (Brown, 1993)
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest ; mountains
Wild timber rattlesnakes can live over 30 years. Captives have lived 37 years.
Range lifespan
Status: captivity: 37 (high) years.
Typical lifespan
Status: wild: 30 (high) years.
Average lifespan
Sex: male
Status: captivity: 30.2 years.
Adult timber rattlesnakes range from 36-60 inches (90-152 cm) in length, and the record length for the species is 74.5 in. (189.2 cm). They exhibit sexual dimorphism; the males are larger, weighing around 2.0 lb. while the females weigh on an average 1.3 lb. There are several color morphs. The background color of the black morph is gray and the patterns are a rich, velvety black. The background color of the yellow morph is tan, the patterns are a sulfur yellow tinged brownish in patches. Western and southern populations have combinations of these two as well. All the snakes have transverse bands of color. The bands vary geographically; eastern, western, and southern types of timber rattlesnake are recognized. (Brown, 1993, Conant & Collins 1998)
Range mass: 500 to 1000 g.
Range length: 90 to 152 cm.
Other Physical Features: heterothermic
Sexual Dimorphism: male larger
Males follow scent trails to find reproductively active females. Once a male finds a receptive female, he rubs the female's neck with his chin and places his body along hers. The male then rapidly jerks his head and body until he can move his cloaca under hers and insert his hemipenis. Copulation may last for several hours. Males may fight for access to a receptive female.
Mating System: polygynous
Most mating occurs in the summer months, from mid-July to October. Females store sperm through the winter for use in the spring when they emerge from hibernation. Females begin the formation of eggs and yolk in the late summer and fall, those eggs then ovulate the following spring. The live young are born in the autumn, from August through October. Timber rattlesnakes are ovoviviparous, meaning that the eggs are incubated and hatched within the female and she gives birth to live, precocial young. Females give birth to 1 to 20 young, usually 6 to 10 (mean of 10.4). Litter size depends on the size of the female, with larger females having more young. Young are 19.5 to 38.3 cm long (mean 32.5), and weigh from 11.2 to 29.1 grams (mean 22.5). The young have similar patterns to adults, but tend to have a grayish hue. They have their first shedding at 7 to 10 days old, at which point they expose a button-like terminal scale where their rattle will eventually grow. Evn newborn young are dangerous, with fangs from 2.6 to 3.8 mm long and a supply of venom.
Males become sexually mature at 4 to 6 years old; females mature at 7 to 13 years old. Males are mature at snout to vent lengths of 90 to 100 cm. Females are mature at snout to vent lengths of over 100 cm in C. h. atricaudatus and 67 to 90 cm in C. h. horridus.
Breeding interval: Females reproduce every 2 to 6 years, most often they mate every 3 years.
Breeding season: Most breeding activity occurs from mid July to October.
Range number of offspring: 1 to 20.
Average number of offspring: 10.4.
Range time to independence: 7 to 10 days.
Range age at sexual or reproductive maturity (female): 7 to 13 years.
Range age at sexual or reproductive maturity (male): 4 to 6 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; ovoviviparous
Average gestation period: 135 days.
Average number of offspring: 9.
Female timber rattlesnakes invest significantly in pre-parturition nutrients and protection of their young. They give birth in birthing rookeries, which are often the same sites as winter hibernacula, and stay with the young for 7 to 10 days after birth. At that point the young disperse and become independent.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
Timber rattlesnake
Cane-brake rattlesnake
Eastern USA (from southeastern Minnesota and southern Maine, southward to east Texas and northern Florida) and southern Canada (southern Ontario) (McDiarmid et al., 1999).
Types: lost, originally in King Adolph Friederic collection and later sent to the Royal Zoological State Museum in Stockholm, Sweden (NHRM) (McDiarmid et al., 1999).
Type-locality: "America." Proposed restriction to "vicinity of New York City" by Schmidt, 1953, Check List N. Am. Amph. Rept., 6th ed., 280pp.[227] (McDiarmid et al., 1999).
The timber rattlesnake, canebrake rattlesnake, or banded rattlesnake (Crotalus horridus)[6] is a species of pit viper endemic to eastern North America. Like all other pit vipers, it is venomous, with a very toxic bite.[7] C. horridus is the only rattlesnake species in most of the populous Northeastern United States and is second only to its relatives to the west, the prairie rattlesnake, as the most northerly distributed venomous snake in North America.[8][9] No subspecies are currently recognized.[10][11]
The timber rattlesnake was one of the many reptile species originally described by Carl Linnaeus in the landmark 1758 10th edition of his Systema Naturae, and still bears its original name Crotalus horridus.[12]
The subspecies C. h. atricaudatus (Latreille in Sonnini and Latreille, 1802), often referred to as the canebrake rattlesnake,[6] is currently considered invalid.[10][13] Previously, it was recognized by Gloyd (1936) and Klauber (1936). Based on an analysis of geographic variation, Pisani et al. (1972) concluded no subspecies should be recognized. This was rejected by Conant (1975), but followed by Collins and Knight (1980). Brown and Ernst (1986) found evidence for retaining the two subspecies, but stating them apart without having more information than usual is not possible, including adult size, color pattern, the number of dorsal scale rows, and the number of ventral scales. Dundee and Rossman (1989) recognized C. h. atricaudatus, but others take a more neutral point of view.[14]
The timber rattlesnake is one of 36 species in the genus Crotalus. This genus can be distinguished from Sistrurus by the small scales atop the head, rather than nine large scales found on Sistrurus. [15]
Adults usually grow to total length of 91–152 cm (36–60 in).[8] In Pennsylvania, the smallest size females that could produce viable eggs was 72.2 cm (28.4 in).[16] Most adult timber rattlesnakes found measure less than 115 cm (45 in) in total length and weigh between 500 and 1,500 g (1.1 and 3.3 lb), often being towards the lower end of that range.[17][18][19][20] The maximum reported total length is 189.2 cm (74.5 in) (Klauber, 1956). Holt (1924) mentions a large specimen caught in Montgomery County, Alabama, which had a total length of 159 cm (62.5 in) and weighed 2.5 kg (5.5 lb).[14] Large specimens can reportedly weigh as much as 4.5 kg (9.9 lb).[21]
The dorsal scales are keeled[22] and arranged in 21–26 scale rows at midbody (usually 25 rows in the southern part of its geographic range, and 23 rows in the northern part). The ventral scales number 158–177 in males and 163–183 in females. Males have 20–30 subcaudal scales, while females have 15–26. The rostral scale is normally a little higher than it is wide. In the internasal-prefrontal area there are 4–22 scales that include 2 large, triangular internasal scales that border the rostral, followed by two large, quadrangular prefrontal scales (anterior canthals) that may contact each other along the midline, or may be separated by many small scales. Between the supraocular and internasal scales, only a single canthal scale is present. Five to seven intersupraocular scales are seen. The number of prefoveal scales varies between two and eight. Usually, the first supralabial scale is in broad contact with the prenasal scale, although slightly to moderately separated along its posteroventral margin by the most anterior prefoveals.[14]
Dorsally, they have a pattern of dark brown or black crossbands on a yellowish-brown or grayish background. The crossbands have irregular zig-zag edges, and may be V- or M-shaped. Often a rust-colored vertebral stripe is present. Ventrally, they are yellowish, uniform, or marked with black.[23] Melanism is common, and some individuals are very dark, almost solid black.[24] The tails of C. horridus are black and can be described as 'velvety.'[25]
Timber rattlesnakes are present in the eastern United States from southern Minnesota and southern New Hampshire, south to East Texas and North Florida.[26] One hundred and fifteen rattlesnakes have been marked within Brown County State Park in Indiana, one of the few places where they can be found in the state.[27]
Its historic range includes southern Ontario and southern Quebec in Canada,[5] but in May 2001, the Canadian Species at Risk Act listed it as extirpated in Canada.[28] A Canadian government sponsored recovery strategy is under study to support the reintroducing of this predator of many pests to its former Canadian habitat.[29]
Many were present in some of the thick forest areas of central and southeastern Iowa, mostly within the Mississippi, Skunk, Iowa, and Des Moines River valleys, in several places in these areas; bites from timber rattlesnakes have been widespread, especially in a localized area of Geode State Park, in southeastern Henry County, along Credit Island Park, in southern Scott County, and in the forested areas of southern Clinton County. The museum at Amana Colony, Iowa, asserts that one founding family lost their firstborn, a daughter, at the age of three, due to a rattlesnake bite she received while playing on a woodpile in the 19th century.
In Pennsylvania, it is not heavily present west of Chestnut Ridge, which is in the Laurel Highlands, nor is it heavily present in the more urban areas of the southeastern corner of the state. Thus, its range does not include Philadelphia and Pittsburgh, the two largest cities in Pennsylvania.[8]
C. horridus is extirpated from Michigan, Delaware, Maine and Rhode Island, and is considered close to extirpation in New Hampshire.
Generally, this species is found in deciduous forests in rugged terrain. C. horridus can be found in a variety of terrestrial habitats including lowland cane thickets, high areas around swamps and river floodplains, hardwood and pine forests, mountainous areas, and rural habitats in farming areas.[25] During the summer, gravid (pregnant) females seem to prefer open, rocky ledges where the temperatures are higher, while males and nongravid females tend to spend more time in cooler, denser woodland with more closed forest canopy.[30]
Female timber rattlers often bask in the sun before giving birth, in open rocky areas known as "basking knolls".[31]
During the winter, timber rattlesnakes brumate in dens and limestone crevices, often together with copperheads and black rat snakes.[24] Timber rattlesnakes exhibit high levels of philopatry to their natural hibernaculum, which means that they are likely to return to the same hibernaculum, or communal wintering den, each year.[32]
Males often mate farther away from winter hibernacula than females.[33]
A lifetime reproduction study of a population in the Adirondack Mountains of New York found that the first reproduction occurs at a mean age of 9.6 years. The mean length of reproductive cycles is 4.2 years, the mean reproductive life span is 9.6 years, and the average fecundity is 7.7 offspring per litter. Nonviable offspring were found in 20% of the field litters. Most females only reproduced one. Macrogeographic differences were observed within the population and may have correlated resource levels influencing growth rates and additionally human encounters could influence survival.[34]
Their prey are mainly small mammals, but may include small birds, frogs, and other small animals, including other snakes. Although capable of consuming other rattlesnakes, the most common snake they prey upon are garter snakes.[30] Like most rattlesnakes, timber rattlesnakes are known to use chemical cues to find sites to ambush their prey and often strike their prey and track them until they can be consumed.[35][36] Timber rattlesnakes are known to use fallen logs as a waiting site for prey to pass by, giving them an elevated perch from which to effectively strike their prey, which is almost entirely terrestrial rather than arboreal (even arboreal prey such as squirrels tend to be caught when they come to the ground).[36][37] If the arboreal prey (squirrels) are in the trees, it was found that the snake might indicate vertical tree posture, meaning it leans up against a tree looking at the squirrel and waiting for it to come down.[38] The primary foods by genera of timber rattlesnakes were as follows: Peromyscus (33.3%), Microtus (10.9%), Tamias (qv) (10.6%), Sylvilagus (10.4%), Sigmodon (5.3%) and Sciurus (4.2%). Based on examination of the snout-to-vent length, juvenile timber rattlesnakes were found to differ slightly in dietary preferences from adult rattlesnakes, being more likely to consume smaller prey such as shrews (averaging 8 g (0.28 oz) and unable to attack subadult eastern cottontail rabbits (averaging 500–1,000 g (1.1–2.2 lb) but Peromyscus was the number one prey item for both young and adult rattlesnakes. Several birds, although always secondary to mammals, are also known to be hunted, mainly ground-dwelling species such as bobwhites, but also a surprising number of passerines.[39]
Prey sometimes exhibit anti-snake displays like tail-flagging, but timber rattlesnakes show no immediate or overt response to these displays. There is no rattling, striking, or other defensive behavior in response to prey anti-snake displays.[40]
Potentially, this is one of North America's most dangerous snakes, due to its long fangs, impressive size, and high venom yield. This is to some degree offset by its relatively mild disposition[41] and long brumation period. Before striking, they often perform a good deal of preliminary rattling and feinting.[42] Cist (1845) described how he lived in western Pennsylvania for many years, and the species was quite common there, but in all that time, he heard of only a single death resulting from its bite.[6]
Considerable geographic and ontogenetic variation occurs regarding the toxicity of the venom, which can be said for many rattlesnake species. Four venom patterns have been described for this species: Type A is largely neurotoxic, and is found in various parts of the southern range. One effect of the toxin can be generalized myokymia.[43] Type B is hemorrhagic and proteolytic, and is found consistently in the north and in parts of the southeast. Type A + B is found in areas where the aforementioned types apparently intergrade in southwestern Arkansas and northern Louisiana. Type C venom has none of the above components and is relatively weak.[41]
The neurotoxic component of the type A venom is referred to as canebrake toxin, and is a phospholipase A2. It is analogous to the neurotoxins found in the venoms of several other rattlesnake species, and when present, contributes significantly to the overall toxicity. Other components found in the venom include a small basic peptide that works as a myotoxin, a fibrinogen-clotting enzyme that can produce defibrination syndrome, and a bradykinin-releasing enzyme.[41]
CroFab antivenom, while not specific for C. horridus, is used to treat envenomations from this species.[44]
The timber rattlesnake was designated the state reptile of West Virginia in 2008.[45] That state's legislature praised "...a proud contribution by the eighth grade class at Romney Middle School, from West Virginia's oldest county, in West Virginia's oldest town, to have been instrumental in making the timber rattlesnake the state reptile..."[46]
This snake became a prominent symbol of American anger and resolve during the American Revolution due to its fearsome reputation. In the 18th century, European-trained doctors and scientists had little firsthand experience with or information on timber rattlesnakes,[47] and treatment of their bites was poorly effective. The motto Nemo me impune lacesset (with the verb in the future tense) appears above a Crotalus horridus on a 1778 $20 bill from Georgia as an early example of the colonial use of the coiled rattlesnake symbol, which later became famous on the Gadsden flag.
This species is classified as least concern on the IUCN Red List (assessed in 2007).[2] Species are listed as such due to their wide distribution, presumed large population, or because they are unlikely to be declining fast enough to qualify for listing in a more threatened category.[48]
The timber rattlesnake is listed as endangered in New Jersey, Ohio, Vermont, Connecticut, Massachusetts,[49] Virginia, Indiana,[50][51] New York,[52] Illinois,[53] and New Hampshire.[54]
In New York, timber rattlesnakes are "extirpated at 26% of historically known dens, and nearly extirpated at another 5%".[55] Brown (1984, 1988) suggested denning populations in New York have been reduced by 50 to 75% of their historical numbers.
In Massachusetts, the snakes are active from mid-May to mid-October.[56] Early settlers were afraid of the snake, as its population was widespread throughout the state. The town of Westborough paid 13 men two shillings per day to rid a local hill of snakes in 1680. The hill had so many rattlesnakes, it was named "Boston Hill" because the number of snakes killed rivaled the population of the young city of Boston.[57] In Milford, men would hunt the rattlesnakes between May and early June. According to Adin Ballou, when he arrived in town in 1824, snakes were still abundant, and by 1881 they were still reported in some areas of town.[58] Since that time their habitat has been reduced to the Blue Hills south of Boston, the Berkshires in Western Massachusetts, and parts of the Connecticut River Valley, notably in the area of the Holyoke Range.[56] The snake is so rare in the state that it is rarely encountered by people and is considered endangered, making it illegal to harass, kill, collect, or possess.[59] In September 2021, a five-foot long timber rattlesnake was recorded on video on a trail in the Blue Hills Reservation.[60]
Timber rattlesnakes have already been extirpated 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.[61] While C. horridus was historically abundant throughout New England, there has been a recent decline in the last known population in New Hampshire that is heading toward extinction because of genetic isolation, inbreeding, and stochastic weather events that render the population susceptible to opportunistic pathogens.[32]
Adult Crotalus horridus, Florida 
Juvenile Crotalus horridus, Florida 
Canebrake rattlesnake, North Florida The timber rattlesnake, canebrake rattlesnake, or banded rattlesnake (Crotalus horridus) is a species of pit viper endemic to eastern North America. Like all other pit vipers, it is venomous, with a very toxic bite. C. horridus is the only rattlesnake species in most of the populous Northeastern United States and is second only to its relatives to the west, the prairie rattlesnake, as the most northerly distributed venomous snake in North America. No subspecies are currently recognized.
