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 Radio tracking Eastern Diamondback Rattlesnakes, Crotalus adamanteus, in Francis Marion National Forest. (photo © Mike Martin)

The field of Herpetology was revolutionized in the early 1970’s through the use of radiotelemetry (Újvári and Korsós, 2000), which, for the first time, allowed biologists to gather long-term detailed data on animal life histories, including home range size, activity patterns, intraspecific interactions, hibernacula use, and thermoregulatory behavior (Nathan et al., 2008; Ward et al. 2013). Recent advancements in GPS technology, however, have provided biologists with an exciting new window into the lives of animals  (Cagnacci et al., 2010; Recio et al., 2011; Tomkiewicz et al., 2010; Urbano et al., 2010; Ward et al., 2013). Due to size issues, GPS tracking has typically been limited to use with large mammals (Recio et al., 2011), but new improvements in miniaturized thechnology has opened even more doors for novel applications.

Admittedly, the unique body shape of snakes (e.g. long, cylindrical body and absence of limbs) poses unique challenges in attaching any external unit. Even so, biologists are beginning to experiment with this methodology and are finding some success (Ciofi and Chelazzi, 1991; Madrid-Sotelo and García-Aguayo, 2008; Martin unpub., 2010; Wolfe unpub., 2016; Wylie et al., 2011). For example, Ernst (2003) used tape and 5-minute epoxy to attach transmitters to the rattles of Prairie Rattlesnakes. Other forms of attachment have been applied to the upper surface of snakes. However, no publications to date report the use of GPS tracking in any snake taxa even though this methodology has great potential to again revolutionize snake field studies, it just needs to be tested.

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A yellow-phase Timber Rattlesnake from Botetourt Co, Virginia

 

The Timber Rattlesnake, Crotalus horridus, has been a model organism in numerous studies (Clark, 2002). In fact, C. horridus was one of the first snakes species to be studied using radio-telemetry (Brown et al., 1982; Galligan and Dunson, 1979). This large-bodied pitviper snake is native to much of the eastern United States, and can be locally abundant sometimes occurring in great numbers at communal den and gestation sites. Throughout much of its’ range, individuals emerge from hibernation between the months of March and May, and remain active for five to seven months, with males spending their active season foraging for prey (mainly small mammals) and searching for mates. Females reproduce every three or four years (Martin, 1993) and during reproductive years they gather at gestation sites known as rookeries. These rookery sites, as well as hibernacula, are selected by snakes based on various geographical features such as aspect, slope, proximity to human disturbance, rock formations and more.

Researchers have found a high level of specialization in these snakes. For instance, individuals use chemical cues to track rodent movements and foraging locations (Clark, 2004; 2007). Furthermore, snake foraging positions and locations are specifically selected based on these chemical cues. So while most people think of snakes such as the Timber Rattlesnake as small-brained, “hard-wired” creatures, as we discover more about the complex functions and secretive lives it’s becoming clear that these snakes are highly sophisticated and specialized on many levels.

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An externally attached GPS transmitter being used by Ashleigh Wolfe of Curtin University to track Pseudonaja affinis. (Photo © Ashleigh Wolfe).

Moreover, C. horridus is a key stone species where it is found, playing a critical role in the ecological function of various habitats. Complex relationships have been noted between the presence of gypsy moths, cycles in oak mast production, variation in rodent populations, and Timber Rattlesnakes (McGowan and Martin, 2004). Crotalus horridus is an apex predator responsible for maintaining ecological equilibrium. A number of factors, including their ecological importance, physiological specialization, and relative wide spread abundance make the Timber Rattlesnake an appropriate organism for a wide range of ecological and biological studies. Furthermore, Crotalus horridus, should be an organism apt for testing the viability of GPS tracking in snakes.

Work Cited:

-Brown BS, Pyle DW, Greene KR, and Friedlaender JB (1982). Movements and temperature relationships of Timber Rattlesnakes (Crotalus horridus) in Northeastern New York. Journal of Herpetology. 16(2):151-161
-Cagnacci F, Boitani L, Powell RA, and Boyce MS (2010). “Animal Ecology Meets GPS-based Radiotelemetry: A Perfect Storm of Opportunities and Challenges.” Philosophical Transactions of the Royal Society B: Biological Sciences 365.1550: 2157-162. The Royal Society Publishing.
-Ciofi C and Chelazzi G (1991). “Radiotracking of Coluber Viridiflavus Using External Transmitters.” Journal of Herpetology 25.1: 37. JSTOR.
-Clark RW (2002). “Diet of the Timber Rattlesnake, Crotalus Horridus.” Journal of Herpetology 36.3: 494. BioOne.
-Clark RW (2004). “Timber Rattlesnakes (Crotalus Horridus) Use Chemical Cues to Select Ambush Sites.” J Chem Ecol Journal of Chemical Ecology 30.3: 607-17. Springer Link.
-Clark RW (2007). “Public Information for Solitary Foragers: Timber Rattlesnakes Use Conspecific Chemical Cues to Select Ambush Sites.” Behavioral Ecology 18.2: 487-90. Oxford Journals.
-Ernst R (2003). “Lethbridge Prairie Rattlesnake Conservation Project: 2002 …” Alberta Sustainable Resource Development, Fish and Wildlife Division, Alberta Species at Risk Report No. 64. Alberta Environment/ Alberta Sustainable Resource Development.
Galligan JH and Dunson WA (1979). Biology and status of Timber Rattlesnake (Crotalus horridus) populations in Pennsylvania. Biological Conservation. 17(1):13-58
-Madrid-Sotelo CA and García-Aguayo A (2008). A simple method for externally attaching radio-transmitters to snakes. North-Western Journal of Zoology. 4(2):335-338
-Martin M (2010) unpublished. Use of external, rattle attached radio transmitters to track juvenile and adult Eastern Diamondback Rattlesnakes, Crotalus adamanteus.                                                                                                                                                                                       -Martin WH (1993). “Reproduction of the Timber Rattlesnake (Crotalus Horridus) in the Appalachian Mountains.” Journal of Herpetology 27.2: 133.
-McGowan EM (2004). Reproductive Strategies of the Timber Rattlesnake.” PhD dissertation, Binghamton University.
-Nathan R, Getz WM, Revilla E, Holyoak M, Kadmon R, Saltz D, and Smouse PE (2008). “A Movement Ecology Paradigm for Unifying Organismal Movement Research.” Proceedings of the National Academy of Sciences 105.49: 19052-9059. Proceedings of the National Academy of Sciences of the United States of America.
-Recio MR, Mathieu R, Denys P, Sirguey P, and Seddon PJ (2011). “Lightweight GPS-Tags, One Giant Leap for Wildlife Tracking? An Assessment Approach.” PLoS ONE 6.12. PLoS ONE.
-Reinert HK, Gylla AM, Mackenzie E, Lauretta MB, and Robert TZ (2011). “Foraging Ecology of Timber Rattlesnakes, Crotalus Horridus.” Copeia. 3: 430-42. American Society of Ichthyologists and Herpetologists.
-Tomkiewicz SM, Fuller MR, Kie JG, and Bates KK (2010). “Global Positioning System and Associated Technologies in Animal Behaviour and Ecological Research.” Philosophical Transactions of the Royal Society B: Biological Sciences 365.1550 (2010): 2163-176. The Royal Society Publishing.
-Újvári B., and Korsós Z (2000). “Use of Radiotelemetry on Snakes: A Review.” Acta Zoologica Academiae Scientiarum Hungaricae 46.2: 115-46.
-Urbano F, Cagnacci F, Calenge C, Dettki H, Cameron A, and Neteler M (2010). “Wildlife Tracking Data Management: A New Vision.” Philosophical Transactions of the Royal Society B: Biological Sciences 365.1550: 2177-185. The Royal Society Publishing.
-Ward MP, Jinelle HS, and Weatherhead PJ (2013). “Evaluation of Automated Radio Telemetry for Quantifying   Movements and Home Ranges of Snakes.” Journal of Herpetology 47.2: 337-45. BioOne.
Wylie GD, Smith JJ, Amarello M, and Cassazza ML (2011). A taping method for external transmitter attachment on aquatic snakes. Herpetological Review. 42(2):187-191
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