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).

Timber rattlesnake

Cane-brake rattlesnake

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 )

occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Absent

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (200,000-2,500,000 square km (about 80,000-1,000,000 square miles)) The range extends from central New England to northern Florida, and west to eastern Texas, central Oklahoma, eastern Kansas, southeastern Nebraska, southern and eastern Iowa, and southeastern Minnesota (Martin, in Tyning 1992; Ernst and Ernst 2003; Campbell and Lamaer 2004). The distribution is spotty along the western and northern edges of the range. Sizeable populations still occur in the Appalachian Mountains from Pennsylvania though the Virginias, across eastern Kentucky and Tennessee to northeastern Alabama, in the Ouachita and Boston mountains of Arkansas and extreme eastern Oklahoma, in heavily wooded sections of the southeastern Coastal Plain from North Carolina to northeastern Florida and west to Louisiana and southern Arkansas, and in the Piedmont in the Uwharrie National Forest of central North Carolina and Pine Mountain of west-central Georgia (Martin, in Tyning 1992). See Martin (in Tyning 1992) for a detailed range map and further details on current known distribution. Dens occur at elevations of up to about 5,000 feet in the southern Appalachians, 2,200 feet in southern New England, and about 1,300 ft in northeastern New York, Wisconsin, and Minnesota; individuals may range to higher elevations in summer (Martin, in Tyning 1992).

Eastern USA (from southeastern Minnesota and southern Maine, southward to east Texas and northern Florida) and southern Canada (southern Ontario) (McDiarmid et al., 1999).

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: ectothermic ; heterothermic ; bilateral symmetry

Sexual Dimorphism: male larger

Length: 189 cm

In areas where no other rattlesnakes of the genera Crotalus (rattlesnakes proper) or Sistrurus (pygmy rattlesnakes) occur, this snake may be distinguished by its rattle. It differs from harmless snakes of similar appearance by having a pit on each side of the face infront of and below the eye. Petersen and Fritsch (1986) provided color photographs and scale diagrams of harmless species commonly mistaken for the timber rattlesnake. One of these species, the milk snake (Lampropeltis triangulum), is slender and has skin that may be described as smooth, shiny, or glossy. In contrast, the timber rattlesnake is heavy-bodied with, keeled scales; overall, a rattlesnake's skin appears coarse-textured, velvety, or dull. Two other species, the northern water snake (Nerodia sipedon), and the astern hognose snake (Heterodon platirhinos), although having keeled scales and a dull texture, lack the distinguishing characteristics of a rattlesnake.

• Terrestrial

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

Comments: In the Northeast, this species inhabits mountainous or hilly deciduous or mixed deciduous-coniferous forest, often with rocky outcroppings, steep ledges, and rock slides (Petersen and Fritsch 1986, Brown 1993). In the upper Midwest, this snake occurs on steep rocky bluffs and bluff prairies with oaks (Breckenridge 1944, Oldfield and Keyler 1989, Vogt 1981). In the central midwest, optimum habitat is a high, dry ridge with oak-hickory forest interspersed with open areas (Minton 1972), and "deciduous forest, especially along hilltop rock outcrops in thick woods" (Fitch 1958). In the South, preferred habitat is "hardwood forests of the type found in Loess Bluff and in many river bottoms" (Cook 1943), swampy areas and floodplains (Mount 1975), wet pine flatwoods, river bottoms and hydric hammocks (Ashton and Ashton 1981), and hardwood forests and cane fields of alluvial plain and hill country (Dundee and Rossman 1989). Fogell et al. (2002) documented a relatively high level of agricultural field use at the western edge of the range in Nebraska. Activity is primarily terrestrial, but timber rattlesnakes sometimes climb into vegetation (see Fogell et al. (2002).

Hibernacula are typically located in a rocky area where underground crevices provide retreats for overwintering, such as a fissure in a ledge, a crevice between ledge and ground, talus (rock slide) below a cliff, open skree slope (fallen rocks not associated with a cliff), or fallen rock (talus or skree) partly covered by soil (Martin 1989). At least in the northeastern part of the range (Reinert 1984, Reinert and Zappalorti 1988, Hammerson and Lemieux 2001), males and nongravid females are primarily forest dwellers and gravid females use open, sparsely forested sites. Similarly, in Wisconsin Keenlyne (1972) reported gravid females using flat slab rocks and grassy, open slopes. This open habitat was not used by males or nongravid females. "Transient habitat" a somewhat arbitrary category, generally is within 200 m of a den. It tends to be broken by the rough topography and rocky terrain near the den site and supports more open woodland with exposed clearings and shelter rocks. This habitat occurs on outcrop knolls (Brown 1989) used as "stop-over" basking locations by rattlesnakes migrating away from a den in spring. This habitat also is used by gravid females during their reproductive year.

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Timber rattlesnakes migrate seasonally between hibernacula and summer habitat. Individuals rarely may migrate up to 7.2 km from their hibernaculum (Brown 1993), but extensive radio-telemetry data for populations in New Jersey (Reinert and Zappalorti 1988) and Connecticut (Hammerson and Lemieux 2001) indicate that males generally stay within 3.6 km of their hibernaculum and females range no farther than 2.3 km.

Neonates evidently find hibernacula by scent-trailing adults (Brown and MacLean 1983, Reinert and Zappalorti 1988, Hammerson and Lemieux 2001).

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)

Comments: Primary food is small mammals, but in the southern part of the range the diet also commonly includes lizards. Sometimes eats birds, bird eggs, and other small animals. Individuals may ambush prey traveling on fallen logs (Reinert et al. 1984). Little or no feeding is done by gravid females (Reinert and Zappalorti 1988).

Anti-predator Adaptations: cryptic

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 81 to >300

Comments: This species is represented by a large number of occurrences (see Martin, in Tyning 1992), though most may not represent populations that are viable in the long term.

100,000 to >1,000,000 individuals

Comments: Adult population size is unknown but presumably exceeds 100,000. This snake is still fairly common in some parts of its range.

Timber rattlesnakes in northern and upland areas commonly hibernate communally. The largest aggregations include about 200 individuals; most are much smaller, typically less than 60. Lowland populations overwinter singly or in small groups.

In areas where communal denning occurs, maximum individual range length, determined by radio-telemetry for complete or nearly complete active seasons in New Jersey and Connecticut, was as follows: 1.9-3.6 km (mean 2.4-2.7 km) in adult males, 0.5-2.6 km (mean 1.1-1.3 km) in nongravid adult females, and 0.3-2.0 (mean 0.8-1.2 km) in gravid females (Reinert and Zappalorti 1988, Hammerson and Lemieux 2001).

These snakes incur a high rate of mortality in their first year. Populations cannot withstand high rates of adult mortality.

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

Comments: Seasonal cycle may be summarized follows for three areas, western Virginia (Martin 1989), northeastern New York (Brown 1989), and central Connecticut (Hammerson and Lemieux 2001): general emergence, 18 April-12 May in Virginia, 7 May-21 May in New York, mid-April to early May in Connecticut general ingress, 1 October-21 October in Virginia, 14 September-1 October in New York, mainly mid-September to late October in Connecticut.

In the south, C. horridus has a longer active season (late spring, summer, and early autumn) than a hibernating season, whereas in the north the hibernating season exceeds the active season in length. In South Carolina, few are seen before mid-May in most years, active as late as November; most often encountered in early evening and at night (Gibbons and Semlitsch 1991). In Florida and Texas, spends 2-3 months at overwintering dens but occurs on the surface during warm periods throughout the winter (Martin, in Tyning 1992).

Activity is primarily diurnal in spring and fall, more crepuscular/nocturnal in summer.

Timber rattlesnakes add a segment to the rattle each time they shed. Adults shed 1-2 times each year, juveniles more frequently.

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.

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 ; gonochoric/gonochoristic/dioecious (sexes separate); 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)

Mating occurs in summer, early or mid-July through late September in Virginia, New York, and Connecticut (Martin 1992, Brown 1995, Hammerson and Lemieux 2001). Young are born usually August-early October. Females reproduce at intervals of 2-5 years (but minimum interval is 3 years in northeastern New York) (Gibbons 1972; Keenlyne 1978; Galligan and Dunson 1979; Fitch 1985; Martin 1988, 1993); the interval may average 3 years in many areas). About 10-75% of the adult females are gravid in a given year (Brown 1991, Martin 1993). Age of first reproduction in females has been reported in several studies as follows: four years in Wisconsin and Kansas (Keenlyne 1978, Fitch 1985), five years in Pennsylvania (Galligan and Dunson 1979), six years in South Carolina (Gibbons 1972), 5-11 years (mean about 8) in northwestern Virginia and vicinity (Martin 1993), and 7-11 years in northeastern New York (Brown 1991, 1993). Litter size varies geographically, as summarized by Fitch (1985) (area, mean, range): northeastern (New York), 9.3, 4-14; northwestern (Wisconsin), 8.4, 3-11; west-central (Kansas), 8.5, 5-14; southeastern (South Carolina), 12.6, 10-16. A combined picture of the reproductive pattern is low-frequency birthing and delayed age of first reproduction.

It should be noted that, as in morphological characteristics and habitat, life history characteristics vary geographically. With longer active season lengths and warmer climates, southern populations of C. horridus may grow faster, mature earlier, and reproduce more frequently than do northern populations. There also is an indication that litter size is larger in southern than in northern populations.

Maximum longevity in northern New York is about 20-25 years (Brown 1991). A captive lived almost 37 years (Cavanaugh, 1994, Herpetol. Rev. 25:70).

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

Canada

Rounded National Status Rank: NX - Presumed Extirpated

United States

Rounded National Status Rank: N4 - Apparently Secure

Rounded Global Status Rank: G4 - Apparently Secure

Reasons: Large range in the eastern United States, but occurrence is spotty in most regions; most populations have been depleted or exterminated by humans, and most are declining.

Intrinsic Vulnerability: Highly vulnerable

Global Short Term Trend: Decline of 10-30%

Comments: Area of occupancy, number of subpopulations, and especially population size probably are still declining, possibly at a rate of more than 10 percent over three generations (roughly 20-30 years).

Global Long Term Trend: Decline of 30-50%

Comments: Declining or extirpated in all northeastern states. In New York, extirpated at 26% of historically known dens, nearly extirpated at another 5% (Stechert, in Tyning 1992). Population in central Connecticut is declining slowly (Fritsch, in Tyning 1992). Survives in at least five population clusters in Massachusetts (French, in Tyning 1992) and just a few in Connecticut (Klemens 1993). One population is known to be extant in New Hampshire (Taylor and Soha, in Tyning 1992), two in Vermont (DesMeules, in Tyning 1992). Extirpated in Rhode Island (Raithel, in Tyning 1992) and apparently also in Maine (Hutchinson and Hunter, in Tyning 1992). There has been a 50-66% loss of known populations in southern New Jersey (Zappalorti and Reinert, in Tyning 1992). Extirpated in about half of the counties in which recorded in Ohio (Wynn, in Tyning 1992). Has declined substantially in Minnesota (Keyler and Oldfield, in Tyning 1992). No careful mark-recapture population estimates have yet been published. One long-term study (W. S. Brown, northeastern New York) will provide such estimates after several more years of field work. What has been clear to date is the difficulty of recapturing individuals other than gravid females regularly. This problem may cause violation of an important sampling assumption of equal catchability of all sizes and age classes, an assumption necessary for population estimates to be valid. Brown (unpubl. data) has recaptured many snakes after long lapses (up to nine years) and it remains to be seen how the problem of inconsistent recaptures will affect calculations. From earliest settlement of the North American continent, hunting rattlesnakes at their dens became a regular habit of many pioneers. Babcock (1929) commented: "It is probably only a matter of time when the timber rattlesnake in New England will share the fate of the passenger pigeon." Recognizing the scarcity of objective data to show trends in numbers, an overall consensus among virtually all scientists and field observers is that the timber rattlesnake indeed is declining over most parts of its range. The first major recent warning was published by Galligan and Dunson (1979) who, on the basis of counts of snakes turned in by snake hunters and on interviews with them at a number of local community-sponsored rattlesnake hunts in Pennsylvania, documented severe declines in timber rattlesnake numbers. Stechert (1982) summarized factors in the historical decline in New York. Brown (1984, 1988) suggested denning populations in New York have been reduced by 50 to 75% of their historical numbers. Martin (1982) stated that most long-term observers feel that most dens are at 15% to 20% levels compared to forty years ago.

Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species

Comments: Summary of primary threats: loss of habitat; habitat fragmentation and isolation of populations, which may become small and nonviable; and direct mortality caused by humans (including illegal snake hunters) and vehicles as habitat is encroached upon by urban/residential development (Brown, in Tyning 1992; Brown 1993).

1. HABITAT DESTRUCTION: In states where the snake is legally protected, housing developments near rattlesnake dens are causing the most serious problem. Current laws generally do not mandate habitat protection for endangered or threatened species. In some areas, persons encountering rattlesnakes in new developments have cooperated with protection efforts by calling persons authorized to catch and transport live rattlesnakes. This is an important factor in successfully protecting rattlesnake populations near developments.

2. MARKET HUNTING: Bounty systems have caused a high level of deleterious exploitation and significant reduction or extirpation of populations by a mere handful of people (W. S. Brown, unpubl. data). In some areas (e.g., Pennsylvania) bounty hunting led to rattlesnake hunting among the general population and became a major outdoor activity promoted by sports and civic groups. Commercial collecting for the pet trade is an ever-present current threat, despite some decline in recent years. Single individuals have been responsible for removal of several thousand snakes (Stechert 1980). Today, a growing number of persons maintain reptiles in private collections. Timber rattlesnakes, beautiful and easily kept in captivity, are much sought-after. Private collectors are supplied by an often illicit network of collectors, dealers, and buyers.

3. SNAKE HUNTING FOR "SPORT," ORGANIZED SNAKE HUNTS OR "ROUND-UPS." In Pennsylvania, organized snake hunts caused injury and cruelty to captured snakes, displacement from familiar range, removal of gravid females from already-depleted populations, and habitat destruction by snake hunters (Galligan and Dunson 1979, Reinert 1988). Despite regulations, timber rattlesnake populations in Pennsylvania were legally "harvested" at a nonsustainable level, leading to the collapse of most den populations (Martin et al. 1990). In response, Pennsylvania regulations were amended such that the open season extends from the second Saturday in June through July 31, with daily bag limit of one snake. These regulations should protect snakes at den sites, prevent stockpiling of snakes, and discourage rattlesnake hunting altogether.

4. SHADING-OVER: In some regions, several investigators believe that "shading over" by the growth of large trees on and near a den may be causing conditions that are incompatible with long-term viability for timber rattlesnakes. According to this view, there is a need for an open, lightly wooded or brushy early successional plant association to provide an optimal denning environment. In contrast, Martin (1990, pers. comm.) says: "Shading over of the den site does not present a problem for snakes at emergence time when the trees are bare or just starting to leaf. The problem is shading over of the rocks that are used as gestating and birthing rookeries." Similarly, in Connecticut, Hammerson (pers. obs.) found that heavy shading (in summer) did not discourage den use, but he observed reduced use of a gestation/birthing site after it was shaded by growing vegetation. The possible threat of shading-over deserves further study, but it seems likely that shading has temporary, localized effects that are insignificant over the long term on a landscape scale.

5. LOGGING: Commercial tree removal may not necessarily cause long-term harm to a timber rattlesnake population's habitat, but can pose a direct threat to the snakes if conducted during the active season (mainly April-October).

6. ROAD MORTALITY: New Jersey Pine Barrens populations suffer from excessive mortality of gravid females due to vehicular traffic on roads and trails (Zappalorti and Reinert, in Tyning 1992). Ill-placed developments and associated new roads and increased traffic can lead to increased mortality of rattlesnakes even in areas several miles from the development.

Restoration Potential: There have been no studies of population dynamics, and no quantitative data to document actual recovery potential. What follows is speculative, but based on sound biological intuition.

Most workers with good knowledge believe depleted populations can recover. The exact minimum viable population size and timing of this recovery are unknown. Minimum population size needed for recovery probably must consist of at least 30 to 40 adults, with at least four or five mature females. Given the late age of maturity and slow rate of reproduction, recovery probably would require many years. If such a small population were completely protected, it might gradually build up to an average den size of 60 to 100 animals with a representative age distribution within twenty to thirty years.

Martin (1990, pers. comm.) reports the following: "One den that had been depressed to about 50 to 60 snakes in 1968 by hunting pressure, had climbed to about 120 to 130 snakes in 1983 [a 15-year interval]." Martin (in Tyning 1992) believed that a minimum of 8 adult females was needed for a population to be viable.

Preserve Selection and Design Considerations: An adequate area of undisturbed summer range habitat surrounding a timber rattlesnake den is vitally important for protecting a viable population. A 1.5-mile radius of protected habitat around a den is adequate for females, but an additional protected zone of one mile beyond this is recommended to accomodate the greater dispersal distances of adult males, which not uncommonly range up to approximately 2.5 miles from their den. This zone extending from 1.5 to 2.5 miles from the den buffer zone might be habitat of lesser quality or it might contain some human incursion. This additional area, even if it consists of moderately disturbed habitat will offer additional protection to the population. Although a 2.5-mile migratory distance as a measure of radial protection from a den applies to many populations, in some areas and at some dens this distance may be less than the distances moved by many snakes in the population. Each specific area should be studied in detail to ascertain the patterns of movements of migrating rattlesnakes. In general, as a working recommendation, an area within 2.5 miles of a den seems critical for protecting most timber rattlesnake populations studied to date.

In many areas it may be impossible to obtain an unbroken circular tract of land around a den, and it also may not be biologically realistic in terms of the snakes' movement patterns. Some populations apparently use "corridors" for their migrations in certain directions, thus making some segments of habitat far more heavily used than others. Timber rattlesnakes seem to avoid difficult sheer ledges that may rim one side of a den, and, where dens are at a lower elevation than summer range, most of the snakes tend to go upslope to areas of higher elevation. Home ranges may be often non-overlapping, or may occur in separate areas of the available habitat, and rattlesnakes may shift their activity areas from one year to the next (W. S. Brown, unpubl. obs.; Hammerson and Lemieux 2001), so known data from short-term studies should not be the basis for truncating the protected zone.

Management Requirements: Specific management strategies include:

SECRECY: It is essential to never reveal the location of hibernating dens to anyone, except for valid reasons (e.g., research or protection). Local media and popular magazine writers, in particular, should not be given specific locality information. More than all other factors, it is this lapse of judgement on the part of those with this sensitive knowledge which has, over the years, led to massive exploitation.

AVOIDING DISTURBANCE: Timber rattlesnakes on their dens and in transient habitats are prone to being disturbed. Repeated visits to den sites or to specific "snake rocks" can put the normal behaviors of these snakes at risk of disruption. Repeated visits to particular rocks frequented by the snakes, and capturing or frightening them at such rocks, will cause abandonment. Thus, visits to den sites and to specific shelter rocks in transient habitats should be curtailed to avoid disturbing the snakes.

PATROLS: Rattlesnakes are especially vulnerable during spring emergence (April-May) and during gestating and birthing (July to mid-September). During these times closing off access to the den itself is an important action. Also, the researcher/manager may want to simply avoid disturbing the animals during these vulnerable periods unless these periods are being used to conduct specific counts for population estimates.

PREVENTING SHADING-OVER: One worker (A. Smith, Jr., pers. comm.) has actively managed one den area by selective removal of larger shade trees in the vicinity of a den. W. B. Allen (1990, pers. comm.) suggested an active management approach to the problem of shading-over: during winter months authorized personnel equipped only with saws could cut vegetation shading the den sites and drop shading trees downhill below the den; cut brush could be dropped at the base of the ledges and left there. However, it is important to note that not all agree that prevention of shading-over of dens is necessary or advisable in all circumstances.

LOGGING IN WINTER: In the vicinity of a den, logging should be restricted to the winter months of November through March where snake are hibernating. This will prevent the snakes' being killed by loggers.

ROAD CLOSURES AND PRUDENT LOGGING: For the New Jersey Pine Barrens, Zappalorti and Reinert (in Tyning 1992) recommended closing certain roads to vehicular traffic (to reduce kills of gravid females) and clearcutting blocks of forest between dens and roads (to provide suitable basking areas other than road sides).

FENCING: Fencing, though somewhat expensive, can be used effectivly to prevent encroachment of rattlesnakes into established vacation "camps" (Brown, in Tyning 1992). However, fencing can reduce or eliminate access to summer habitat and should not be used to facilitate new developments.

TRANSLOCATION: Translocation could be effective in restoring a viable population in historical sites that still have favorable habitat, but translocations of reptiles generally have had poor success; justification for such a project should be closely examined and any translocations should be closely monitored (Brown, in Tyning 1992). In Pennsylvania, Reinert and Rupert (1999) found that translocated snakes experienced lower survival and exhibited much greater movements than did resident individuals in the same area. The snakes did locate active hibernacula, apparently by following resident snakes. The authors did not recommend translocation as a standard conservation practice because of its immediate and long-term negative impacts. Hammerson believes that successful translocation and reestablishment of an extirpated population likely would require multi-year release of neonates at a historical den site.

Management Programs: There are active management programs underway:

Elmira, NY: Den on-site. Protection, secrecy, patrolling, and vegetation thinning. Contact: Arthur Smith, Jr., Elmira, NY; or Central New York Chapter, TNC (315 Alexander Street, Rochester, NY 14604).

West Haven, VT: Den on-site. Protection, secrecy, patrolling. Contact: Marc Des Meules, Vermont Field Office, TNC. Town of Bolton, NY: Summer range, den not on-site. Protection. Contact: Margaret Olsen, Eastern New York Chapter, TNC (1736 Western Ave., Albany, NY 12203).

Central Connecticut: Protection, secrecy, patrolling. Contact: Doug Fraser, Siena College, Loudenville, NY, or Julie Victoria, CT Department of Environmetal Protection, or Geoffrey Hammerson, NatureServe..

Monitoring Programs: Active (or recent) monitoring/research programs on timber rattlesnake populations are being conducted in the following states: VA, MD, WV, NC: Martin. MA: Tyning, Stechert. CT: Hammerson, Gruner, Fritsch, Fraser, Petersen, Stechert, Klemens. NH: Taylor, Stechert. NJ: Stechert, Zappalorti. NY: Stechert, Brown, Breisch, A. Smith, Peterson. IL: Storment. PA: Harwig, Martin, Stechert, Reinert, W. Smith. KS: Fitch, Pisani. VT: Des Meules, Stechert. OH: McDuffie, Moody, Hall, Wynn. MO: Sexton, Drda. MN: Reyler, Oldfield.

Management Research Programs: There are several research programs underway, generally by the same individuals listed in the monitoring section.

Management Research Needs: Research is needed on the following:

(1) Quantitative data on population densities; mark-recapture estimates of population sizes of denning colonies including tests of assumptions of random sampling;

(2) Long-term comparative measures of population trends;

(3) Reproductive biology of females: age of first reproduction, reproductive frequency, litter size;

(4) Age-specific survivorship, particularly among newborn and in the first year;

(5) Factors causing mortality: Assessment of role of density-dependent and density-independent factors;

(6) Detailed seasonal movements of adults in communally denning populations;

(7) Mechanisms of den-finding in newborn; movement patterns of newborn from birth site to den;

(8) Ability of translocated or introduced rattlesnakes to "take to" and become established in a historical site or formerly extirpated den.

Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: At least several occurrences are protected.

Needs: Protect all known denning areas and adequate surrounding foraging habitat (generally a radius of about 1.5-2.5 miles from the den site) (see Brown 1993). Foster protection through public education. Do not reveal den locations to the general public or unknown persons.

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

Comments: Venomous but not aggressive, defensive if disturbed; human fatalities have resulted from bites (Ernst 1992).

Stewardship Overview: The timber rattlesnake is a long-lived and slow-maturing ectothermic vertebrate. It has a low reproductive rate and a relatively long mean generation time. These demographic traits are the main reasons why recovery of depleted populations will be slow. Many populations have been exterminated since colonization of the North American continent, and most remaining denning colonies have been reduced drastically in numbers through organized snake hunting and commercial collecting for the exhibit and net trades. The chief threat today is land development and habitat destruction.

The spatial and seasonal biology are centered on its den, where an entire population undergoes communal hibernation through the winter months. The snakes are seasonally migratory, moving away from their den in spring and back to it in autumn. Protecting a viable population depends on protecting the den itself as well as adequate areas of habitat around the den. Males use a home range area of approximately 500 acres, nongravid females of 100 acres. Protecting an area of 2.5 miles in radius around a den (19.6 square miles total area) is recommended as necessary to safeguard a timber rattlesnake population. A 1.5-mile radius (seven square miles total area) will protect most females, but may not be adequate for protection of the entire population. A circular area may not be strictly required in all cases, as certain migration directions and elevations may be preferred over others.

The main ways to manage and safeguard known populations of this species are: (1) Protecting the snake at its known denning colonies through vigilance; (2) Maintaining Secrecy by not revealing to anyone localities of den sites; (3) Avoiding Disturbance of the snakes by restricting or preventing humans from visiting dens and transient habitats; (4) Patrolling the area during vulnerable times, particularly the spring emergence period and the summer gestating and birthing period; and (5) Vegetation thinning to prevent shading-over at some den sites.

Comments: Pisani et al. (1972) examined morphological variation in primarily the midwestern portion of the range and concluded that the recognition of subspecies is not warranted. Brown and Ernst (1986) examined mostly eastern specimens and concluded that the upland and lowland forms (subspecies horridus and atricaudatus, respectively), are taxonomically distinct, at least in the portion of the range east of the Appalachians. Clark et al. (2003) examined mtDNA variation and found that distinct mtDNA lineages are evident, but the divergences are not deep and the lineages do not correspond with the traditional subspecies.