Species Action Plan - Pennsylvania Fish and Boat Commission_1_

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					               Species Action Plan                                             Timber Rattlesnake
               Natural Diversity Section                                               June 2011

     Species Action Plan:
       Timber Rattlesnake
       (Crotalus horridus)

Purpose: This plan provides an initial five
year blueprint for the actions needed to
attain near-term and, ultimately, long-term
goals for the conservation and recovery of
                                                 Figure 1. Timber rattlesnake (Crotalus
the timber rattlesnake. The action plan is a     horridus). Photo by Steve Shaffer.
living document and will be updated as
needed to reflect progress toward those           shape of chevrons, but at the anterior portion
goals and to incorporate new information as       of the body the bands may instead be broken
it becomes available.                             to form blotches (one mid-dorsal and two
                                                  lateral). The crossbands are typically
Goals: The immediate conservation goal for        outlined with light yellow scales. A faint
the timber rattlesnake is to identify and         chestnut-brown, mid-dorsal stripe is often
maintain the rattlesnake populations that are     evident. The tail is black, both dorsally and
under greatest threat in Pennsylvania. The        ventrally, and in most specimens there is
long-term recovery goal is to increase            considerable darkening of the coloration and
viable, reproducing populations of timber         pattern in the posterior quarter of the body.
rattlesnake and ultimately, to remove the         The venter is lighter in color than the
timber rattlesnake from the lists of              dorsum, particularly anteriorly, and some
Pennsylvania endangered, threatened and           individuals have a white chin (Hulse et al.
candidate species (58 Pa Code §75).               2001). Newborns are always crossbanded
                                                  with dark markings on a light gray ground
                                                  color. At birth, rattlesnakes have a single
          Natural History
                                                  rattle segment (button) at the tip of their tail.
                                                  One additional segment is added to the base
Taxonomy: Class Reptilia, Order Squamata          of the rattle with each molting. It is common
(lizards and snakes), Family Viperidae (pit       for older (posterior) segments of the rattle to
vipers), Timber Rattlesnake (Crotalus             break off, and rattles rarely consist of more
horridus)                                         than 14 segments. Adults average 90-120
                                                  cm (35-47 inches) in total length with
Description: The general coloration consists
                                                  Pennsylvania specimens rarely exceeding
of dark brown or black crossbands on a
                                                  150 cm (60 inches). Adult males average
ground color of sulfur yellow, brown, gray,
                                                  greater lengths than adult females (Reinert
or black. The crossbands frequently take the

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               Species Action Plan                                            Timber Rattlesnake
               Natural Diversity Section                                              June 2011

                                                  sites that are used by snakes following
Habitat: In Pennsylvania C. horridus              spring emergence are typically located
inhabits deciduous, hardwood forest               within 200 m (~ 655 feet) of the
(Reinert, 1984a). Suitable habitat for C.         hibernaculum. The high visibility and
horridus in Pennsylvania consists of three        density of snakes at such sites have often
major components: 1) overwintering sites          caused basking sites to be mistakenly
(hibernacula), 2) gestation/basking sites, and    identified as hibernacula (dens) in
3) foraging areas.                                Pennsylvania.

Overwintering hibernacula are typically           Foraging habitat is typically composed of
located on forested, rocky hillsides having a     deciduous forest having canopy cover
southeastern to western exposure. However,        averaging nearly 70% closure (Reinert,
hibernacula are not restricted to such areas      1984b). Males and non-gravid females
and several hibernacula have been                 spend the bulk of their active season in such
discovered on north- facing slopes (H.            habitat. Rocks are not an essential structural
Reinert, pers. obs.). The area immediately        element of foraging habitat; however, the
surrounding most hibernacula is densely           availability of fallen logs that serve as
forested by a broadleaf, deciduous over           ambush sites for rodents may be an
story. The hibernaculum itself may consist        important characteristic of good foraging
of a single large rock isolated from other        habitat (Reinert et al., 1984). Radio
outcroppings or it may be a dispersed rocky       telemetry studies (Reinert and Rupert, 1999)
area of small to moderate boulders. In some       have found foraging animals in eastern
cases the hibernacula’s entrance is a single      Pennsylvania range an average of 1700 m
hole in the ground, resembling a small            (1.0 mile) from their hibernaculum over the
mammal burrow, appearing not to be                summer season, but may travel as far as
associated with any visible rock structure.       7000 m (4.3 miles). Complete season
In outward appearance these sites are             foraging ranges encompass an average of
usually indistinguishable from dozens of          105 ha (260 acres) for males and 50 ha (124
other similar areas on the slopes. However,       acres) for non-gravid females.
many hibernacula appear to be located near
topographic depressions that eventually lead      Life History: The timber rattlesnake is a
to spring seeps farther down slope (H.            long-lived (> 30 years), late-maturing (5-9
Reinert, pers. obs.).                             years) species with a low reproductive rate
                                                  (small litters produced at 3 year intervals).
In Pennsylvania most basking sites are            C. horridus is exothermic with low energy
rocky, open areas (< 20% over story canopy        requirements, and it remains inactive during
closure) and exposed rock ledges (Reinert,        a 5-6 month overwintering period annually
1984b). These areas typically have a              (Hulse et al., 2001).
southerly exposure, but this does not appear
to be an essential characteristic. Basking        Emergence from hibernation typically

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               Species Action Plan                                                  Timber Rattlesnake
               Natural Diversity Section                                                    June 2011

begins in April with a return to hibernacula            through September. Females produce broods
beginning in late September. Individual C.              of eight young on average once every three
horridus establish a strong affinity for a              to five years (Hulse et al., 2001).
particular hibernating site and will return to
the same site every winter, possibly for their               Distribution and Status
entire lifetime. Genetic studies indicate that
C. horridus exhibit a metapopulation
structure where hibernacula represent local             National Distribution: Crotalus horridus is
populations linked to nearby hibernacula                distributed widely from New Hampshire
through gene flow mediated by landscape                 southward through the Appalachian
features such as available basking sites                Mountains to northern Florida and westward
(Bushar et al., 1998).                                  along the Gulf Coast to eastern Texas,
                                                        Oklahoma, and Kansas. In the Midwest it is
In contrast to the rest of the population,              found as far north as Minnesota and
gravid female C. horridus will occupy                   Wisconsin within the Mississippi River
basking sites throughout most of the active             drainage and in southern Illinois, Indiana,
season. The movements of gravid snakes are              and Ohio (Ernst and Ernst, 2003).
not extensive because they do not forage
during the later periods of gestation
(Reinert et al., 1984).

The diet of C. horridus consists
predominantly of small mammals which
are captured by ambush. White-footed
mice (Peromyscus leucopus), Red-
backed Voles (Clethrionomys gapperi),
Meadow Voles (Microtus
pennsylvanicus), Pine Voles (Microtus
pinetorum), and Chipmunks (Tamias
striatus) form the bulk of the diet;
however, red squirrels, gray squirrels,
and small rabbits are also taken by the
larger males.

Mating occurs from mid-July through
September (Brown, 1995). Females store
sperm and ovulation occurs after                 Figure 2. Distribution of the timber rattlesnake
emergence from hibernation the                   (Crotalus horridus) in North America (Source:
following spring (Brown, 1991).                  NatureServe 2010).
Parturition may occur from mid August

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              Species Action Plan                                             Timber Rattlesnake
              Natural Diversity Section                                               June 2011

Pennsylvania Distribution: Presently,
C. horridus is restricted to the heavily
forested mountains that transverse the
central portion of the Commonwealth
in a wide band from northeast to
southwest. The leading ridge of the
Appalachian Mountains (the
Kittatinny Ridge) currently defines
the southern extent of the range with
the exception of the South Mountain,
which is an extension of the Blue
Ridge Mountain chain, entering           Figure 3. Distribution of the timber rattlesnake (Crotalus
southern Pennsylvania near Blue          horridus) in Pennsylvania (Source: PFBC 2010).
Ridge Summit and spanning northeast along
the Franklin/Adams, Cumberland/Adams,               Other States Legal Status: In the northeast,
Cumberland/York County boundaries, for              the timber rattlesnake is extirpated from
40 miles to US Route 15. Rattlesnakes are           Maine, Rhode Island, and Ontario. It is
now absent from all of the Piedmont and             listed as state endangered in New
Atlantic Coastal Plain Provinces in the             Hampshire, Vermont, Massachusetts,
southeast. The western slopes of the                Connecticut, Ohio, and New Jersey. It is
Allegheny High Plateau and Pittsburgh               listed as threatened in New York, and
Plateau Sections of the Appalachian Plateau         considered a species of concern in West
Province define the western edge of the             Virginia and Maryland.
                                                           Management Status
In comparison to many states within its
range, C. horridus continues to persist in
relatively large population densities across       The status of C. horridus was one of the first
some regions of Pennsylvania, though these         non-game issues addressed by the
populations are highly disjunct.                   Pennsylvania Fish and Boat Commission in
Consequently, Pennsylvania may function as         1974. The snake has remained a constant
a stronghold for the continued survival of         topic of discussion, controversy, and
this species (Reinert 2005).                       regulatory action within the Agency. With
                                                   the aid of the Pennsylvania Wild Resource
Pennsylvania Legal Status: Candidate (58           Conservation Fund, the PFBC had initiated
Pa. Code §75.3), Possession limits and             several projects in the past two decades that
permit (58 Pa. Code §79.6).                        provided information useful for the
                                                   conservation of C. horridus. These included
                                                   studies of organized rattlesnake hunts, the

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               Species Action Plan                                             Timber Rattlesnake
               Natural Diversity Section                                               June 2011

effect of translocation on C. horridus, the        2) Fragmentation of populations
genetic structure of selected C. horridus            a. New road construction
populations, and an assessment of the                b. High vehicular traffic on previously
characteristics of C. horridus hibernacula.              low volume roadways
The State Wildlife Grant Program currently           c. Other development
is funding ongoing research concerning the
status of historic rattlesnake sites, locating     3) Targeted mortality
new sites in gap areas by conventional on            a. Wanton killing and destruction of
the ground research teams, and the use of               rattlesnake habitat.
radio tracking of individual snakes in gap           b. Poaching of individual snakes, e.g.,
areas. Another State Wildlife Grant funded              timber rattlesnakes are sought in the
project is focused on the genetic aspects of            black market trade.
timber rattlesnakes in Pennsylvania. This
project’s goal is to identify the genetic              Conservation and Recovery
differences and the potential isolation of
metapopulations within the Commonwealth.
The Pennsylvania Department of                     1) Compile state-wide location data of
Conservation and Natural Resources                    viable timber rattlesnake populations.
(Bureau of Forestry) supported another                a. Complete the PFBC survey of
study to examine the impact of commercial                 historic timber rattlesnake sites.
timbering operations on rattlesnake                   b. Investigate statewide gap areas for
populations (Reinert 2008).                               the presence of timber rattlesnakes.

                                                   2)   Identify and prioritize timber
                                                        rattlesnake populations that are
                                                        currently being threatened by
                                                        anthropogenic activities.
1) Habitat
  a. Natural resource extraction and               3)   Analyze existing monitoring data to
     associated infrastructure development              assess both the short and long term
  b. Construction of residential and                    trends in timber rattlesnake populations.
     commercial developments
  c. Loss of gestation sites due to forest         4) Continue and expand ongoing protection
     succession                                       measures for timber rattlesnake
  d. Habitat destruction or disturbance in            populations.
     hibernacula areas                                a. Review and comment on permit
  e. Increase of human activity within                   applications that involve proposed
     habitat range                                       temporary and/or permanent
                                                         disturbances to known habitat areas.

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                Species Action Plan                                           Timber Rattlesnake
                Natural Diversity Section                                             June 2011

      i.     Mitigate for both direct and           7) Review the regulations and policies
             indirect impacts to the timber            concerning the timber rattlesnake and
             rattlesnake habitat.                      provide recommendations as deemed
     ii.     Spot check projects to confirm            necessary.
             adherence to recommended
             mitigation actions.                                 References
   b. Develop best management practices.
   c. Continue to manage/enforce the
         PFBC Venomous Snake and                    Brown, W. S. 1991. Female reproductive
         Organized Hunt Permits.                       ecology in a northern population of the
5) Maintain and expand cooperative                     timber rattlesnake, Crotalus horridus.
   working relationships with Federal and              Herpetologica 47: 101-115.
   PA State agencies regarding
   conservation practices of timber                 Brown, W. S. 1995. Heterosexual groups
   rattlesnake populations on public lands.            and the mating season in a northern
   a. Work with state and federal partners             population of timber rattlesnakes,
         to require the adoption of a no-kill          Crotalus horridus. Herpetological
         policy for contractors, sub-                  Natural History. 3:127-133.
         contractors, and their respective field
         employees while working on                 Bushar, L. M., H. K. Reinert, and L.
         publicly owned lands.                         Gelbert. 1998. Genetic variation and
   b. Assist with the development and                  gene flow within and between local
         implementation of habitat                     populations of the Timber Rattlesnake,
         maintenance and /or habitat                   Crotalus horridus . Copeia 1998:411-
         improvement programs for specific             422.
         management units, targeting existing
         gestation sites.                           Ernst, C. H. and E. M. Ernst. 2003. Snakes
   c. Work with supervising foresters on               of United States and Canada.
        public lands to notify PFBC                    Smithsonian Books, Washington, D. C.
        immediately if field crews encounter
        high concentrations of rattlesnakes         Galligan, J. H. and W. A. Dunson. 1979.
        (>4 rattlesnakes in 2 m2 area).                Biology and status of Timber
   d. Cooperate with design and review of              Rattlesnake (Crotalus horridus)
         timber rattlesnake research on public         populations in Pennsylvania. Biological
         lands.                                        Conservation 15:13-58.

6) Provide outreach to the public to provide        Hulse, A. C., C. J. McCoy, and E. Censky.
   information and promote tolerance of the            2001. Amphibians and Reptiles of
   timber rattlesnake.                                 Pennsylvania and the Northeast. Cornell
                                                       University Press, Ithaca, NY.

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              Species Action Plan                                            Timber Rattlesnake
              Natural Diversity Section                                              June 2011

NatureServe. 2010. NatureServe Explorer:           Reinert, H. K. 2008. The impact of
   An online encyclopedia of life [web                commercial logging operations on
   application]. Version 7.1. NatureServe,            timber rattlesnakes (Crotalus horridus)
   Arlington, Virginia. Available                     in Pennsylvania. Report submitted to               Pennsylvania Department of
   (Accessed: April 21, 2011 ).                       Conservation and Natural Resources.

Reinert, H. K. 1984a. Habitat separation           Reinert, H. K. and R. R. Rupert, Jr. 1999.
   between sympatric snake populations.               Impacts of translocation on behavior and
   Ecology 65:478-486.                                survival of Timber Rattlesnakes,
                                                      Crotalus horridus. Journal of
Reinert, H. K. 1984b. Habitat variation               Herpetology 33:45-61
   within sympatric snake populations.
   Ecology 65:1673-1682.                           Reinert, H. K., D. Cundall and L. M.
                                                      Bushar. 1984. Foraging behavior of the
Reinert, H. K. 1985. Timber Rattlesnake,              Timber Rattlesnake, Crotalus horridus .
   Crotalus horridus Linnaeus. Special                Copeia 1984:976-981.
   Publication of Carnegie Museum of
   Natural History Number 11:282-285.

Reinert, H. K. 1990. A profile and impact
   assessment of organized rattlesnake
   hunts in Pennsylvania. Journal of the
   Pennsylvania Academy of Science

Reinert, H. K. 1991. Translocation as a
   conservation strategy for amphibians and
   reptiles: some comments, concerns, and
   observations. Herpetologica 47:357-363.

Reinert, H. K. 2005. Timber Rattlesnake:
   CWCS priority species account.
   Pennsylvania’s Wildlife Action Plan
   version 1.0.a. Pennsylvania Game
   Commission and Pennsylvania Fish and
   Boat Commission, eds.

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