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 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.
Adult Food Habits: Carnivore Immature Food Habits: Carnivore Food 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.
Little or no feeding is done by gravid females Reinert and Zappalorti In the south, C. 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 In Florida and Texas, spends months at overwintering dens but occurs on the surface during warm periods throughout the winter Martin, in Tyning Timber rattlesnakes add a segment to the rattle each time they shed.
Adults shed times each year, juveniles more frequently.
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Length: centimeters Economic Attributes Economic Comments: Venomous but not aggressive, defensive if disturbed; human fatalities have resulted from bites Ernst Management Summary 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 acres, nongravid females of acres. Protecting an area of 2. 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.
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.
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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.
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If such a small population were completely protected, it might gradually build up to an average den size of 60 to animals with a representative age distribution within twenty to thirty years. Martin , pers. This zone extending from 1. This additional area, even if it consists of moderately disturbed habitat will offer additional protection to the population. Although a 2. 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. 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. 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.
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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. During these times closing off access to the den itself is an important action. Smith, Jr. Allen , pers. However, it is important to note that not all agree that prevention of shading-over of dens is necessary or advisable in all circumstances. This will prevent the snakes' being killed by loggers.
However, fencing can reduce or eliminate access to summer habitat and should not be used to facilitate new developments. In Pennsylvania, Reinert and Rupert 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.
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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. Monitoring Requirements: Long-term monitoring is necessary to show population trends over time scales appropriate for long-lived species such as Crotalus horridus.
The most uniform procedures recommended for comparable monitoring between areas are: 1. Sighting Rate: for example, number of snakes detected per hour. Capture Index: Trends may be shown over seasons, and between months, by calculating the number of snakes caught per capture day. A capture day is defined simply as any day on which at least one rattlesnake is caught Brown , Martin et al. In some populations, the percentage may be even smaller G.
Hammerson, pers. Estimates of population sizes of dens have been made in several areas using a combination of the estimated proportions of the snakes visible on the surface, and repeated observations over a sampling period of several years. In their recent extensive survey of the timber rattlesnake in Pennsylvania, Martin et al.
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Spring Sampling: Counts of rattlesnakes seen on or near a den should be made at three-day intervals for about a three-week period during the snakes' peak emergence period varies with latitude and elevation. A healthy den 30 to individuals should produce roughly eight to 15 individuals seen on at least several days.
Summer Sampling: Counts of gravid females may be made in August in transient habitat near a den.
In conducting visual sampling at such a den area, approximately four or five visits might be made, at weekly intervals or less, to achieve a reliable count of gravid females. Summer Sampling: Sampling summer range will not prove to be productive by standard snake-searching methods. Only occasionally will a rattlesnake turn up. But if spots occur that attract rattlesnakes, it is usually worth checking them. Sites such as rocky clearings, rock walls along roads or fields, rock piles, quarries, and cleared spots in housing developments are good candidates for locating a rattlesnake on summer range.
Because of annual variation in use by rattlesnakes, these sites will require a year period of monitoring to provide a realistic estimate of relative abundance. Interviews with Local Residents: Where rattlesnake distributions are not well known, asking local people if they occasionally or regularly see or kill rattlesnakes is worthwhile. If their residences are within rattlesnakes' summer migratory range, at least one local resident will probably report that they do.
About three residents living in proximity should be interviewed, and, if all report no sightings, very likely no rattlesnakes exist in the region. See Sadighi et al. 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.
Such evidence minimally includes collection or reliable observation and documentation of one or more individuals in or near appropriate habitat where the species is presumed to be established and breeding. Use of a site as a hibernaculum should be confirmed by multiple observations or ideally by information from radio-tagged individuals. Separation Barriers: Consistently busy highway; highway with obstructions impassable to a snake; major river with strong, persistent current; urbanized area dominated by buildings and pavement.
A lesser distance can be used if radio telemetry data indicate than populations using different hibernacula less than 7 kilometers apart are separated by a distinct gap and are not likely to come into contact with one another; additionally, hibernacula more than 7 km apart are part of the same occurrence if the summer home ranges of populations from the two hibernacula are known to overlap ; 2 occurrences separated by more than 7 kilometers of suitable habitat between observation sites for individuals of unknown hibernaculum origin or for populations in which communal denning does not occur; 3 occurrences separated by separated by more than 1 km of moderately unsuitable habitat occasionally traverseable by low numbers of individuals.
Separation Justification: Brown reported that adult male C. Brown did not describe his methods, but the data evidently were based on recaptures of individuals marked by ventral scale clipping. Martin reported that rattlesnakes in Virginia were found up to 5. Intensive studies of radio-tagged individuals in New Jersey Reinert and Zappalorti and Connecticut Hammerson and Lemieux indicate that male timber rattlesnakes generally range less than 3.
In accord with these data, maximum length of representative full-season activity areas for several radio-tracked C. Other studies of radio-tagged C.
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Evidence of genetic differentiation among populations in hibernacula within a few kilometers of each other Bushar et al. In Pennsylvania, Bushar et al. However, individuals in hibernacula separated by more than m may use a common birthing area, suggesting that in such cases the populations should be combined as a single sub-occurrence William H.
Martin, pers. The value of m is a somewhat arbitrary distance that seems to be practical for managing data for different hibernacula. Separation distance for Birthing Area has not yet been determined.