Herpetology Notes, volume 8: 485-487 (2015) (published online on 03 October 2015)
Ploughshare Tortoise (Astrochelys yniphora) natural entrapment
Andrea Currylow1,*, Andrew D. Walde2, Fidelis Filazaha3, Angelo Mandimbihasina4 and Lance Woolaver4
The Ploughshare Tortoise (Astrochelys yniphora; Vaillant, 1885) is the largest extant endemic tortoise on the island of Madagascar. The species is isolated to a small area of mixed palm-savanna, bamboo-scrub, and dry deciduous forest of less than 160 km2 on the northwest coast (Mandimbihasina and Woolaver, 2014). Due to its rarity and attractive golden carapace, it has become an obsession among rare-wildlife collectors. This pressure from the international pet trade and its highly restricted distribution has given the Ploughshare Tortoise the unfortunate privilege of being the most endangered tortoise on the planet (Juvik et al., 1981; Hoogmoed and Vliet, 1985; Curl, 1986; Rhodin et al., 2011; Kiester et al., 2013). The greatest risk to the survival of a wild chelonian population is the loss of the adults, which solely contribute to the sustainability of a population (Congdon et al., 1993; 1994; Doak et al., 1994). Adults are now beginning to be more commonly found for sale in illicit online pet markets and recent population surveys have shown a significant decline of the wild adult population (Kiester et al., 2013; Mandimbihasina and Woolaver, 2014). Because the life-history of tortoises include delayed maturity coupled with an extremely long generation time equating to a slow reproductive rate, reproductive adults are critical to the recovery of the
Department of Biological Science, University of Southern California, Los Angeles, California, USA 2 Turtle Survival Alliance, Ft. Worth, Texas, USA 3 Comité Local du Parc, Baly Bay National Park, Soalala, Boeny Region, Madagascar 4 Durrell Wildlife Conservation Trust, ����������� Lot �������� IIY49 J Ampasanimalo, BP 8511 Antananarivo 101, Madagascar * Corresponding author e-mail:
[email protected] �������������������� 1
population (Pedrono et al., 2004). Therefore, it is crucial that adult animals remain in good health within the wild populations. Herein, we describe an adult Ploughshare Tortoise found in peril in the wild. As part of ongoing monitoring studies of Malagasy tortoises (Currylow, 2014; Mandimbihasina and Currylow, 2014; Walker et al., 2014), we have been conducting radiotelemetry tracking of wild Ploughshare Tortoises since early 2012. On 9 March 2014 at 16h30, we discovered an adult male Ploughshare Tortoise entrapped between two young Combretaceae trees, Terminalia boivinii. The animal had apparently attempted to traverse the gap when the width of its shell prevented clearance. Upon attempts to free itself, the animal scraped the earth away from under its feet, causing it to become suspended in place and hopelessly entrapped (Figure 1). We are unaware of how long the animal remained in that position before we found and freed it. At the time of discovery, the ground temperature was 32.2 °C, air temperature 31.2 °C, ground humidity 88.8%, cloud cover 10%, and canopy cover over the animal was estimated at 80%. The nearest conspecifics found that day were two adult females radio-tracked within one hour and which were no more than 200 meters from the entrapped male. All three animals were in microhabitat classified as dense bamboo and shrub thicket at the time of encounter. A growing urban-wildlife interface means it is not terribly unusual for wild animals to become inadvertently entrapped, especially due to anthropogenic habitat alterations or devices. For example, in 1992 dozens of the closely related Radiated Tortoise (Astrochelys radiata) succumbed to overexposure in southern Madagascar when they fell into an inadvertently created pitfall trap as part of new road construction (Goodman et al., 1994). Cattle grates along livestock fences also act as pitfall traps, trapping and killing Angulate Tortoises (Chersina angulata) and Padloper Tortoises
486
Andrea Currylow et al.
Figure 1. An adult male Ploughshare Tortoise (Astrochelys yniphora: AY0021M) found suspended between two small trees within its native range in northwest Madagascar. (Photographed by FF).
(Homopus sp.) in South Africa (J. Juvik pers. comm.). More exceptional however, are the instances such as that reported herein where herpetofauna may perish through becoming naturally entrapped. Rorabaugh (2003) described a Common Chuckwalla (Sauromalus ater) which became skewered by an agave plant after an apparent fall or leap from a nearby rock outcrop. Wilson and Topham (2009) report discovering two separate Mojave Desert Tortoise (Gopherus agassizii) carcasses wedged vertically (head-down) in basalt flow rock fractures, apparently having died from exposure after falling and becoming stuck in the rock crack. This latter observation is similar in nature to one made by Riedle et al. (2010), whereby two of 29 radio-tracked Desert Tortoises tumbled down a steep rocky hillside in the Sonoran Desert, leading to their eventual death from apparent overexposure as they were unable to right themselves in the rocky terrain. Like many tortoise species, the Ploughshare Tortoise has adapted to undergo months-long periods of inactivity during the dry season. However, because these animals live in extreme environments, entrapment in the wrong place has the potential to turn fatal within hours. Fortunately, the animal we discovered appeared to be in good health and was in an area of relatively high canopy cover, so was likely not at immediate risk of overexposure to direct sunlight. Acknowledgements. We thank Dr. Edward Louis, Jr. with Madagascar Biodiversity Partnership and Madagascar National Parks for local support of our fieldwork. Funding for associated
fieldwork has been awarded by the Turtle Conservation Fund, Conservation International, Turtle Conservancy, U.S. Fish & Wildlife Service, University of Southern California, and personally by the authors. Equipment donations were provided by IDEA WILD, the Turtle Survival Alliance, and Holohil Systems Ltd. We would like to thank the personal support of our efforts by Drs. A. Ross Kiester, James Juvik, and Craig Stanford.
References Congdon, J.D., Dunham, A.E., Sels, R.C.V. (1993): Delayed sexual maturity and demographics of Blanding’s Turtles (Emydoidea blandingii): implications for conservation and management of long-lived organisms. Conservation Biology 7: 826−833. Congdon, J.D., Dunham, A.E., Sels, R.C.V. (1994): Demographics of common snapping turtles (Chelydra serpentina): Implications for conservation and management of long-lived organisms. American Zoologist 34: 397−408. Curl, D.A. (1986): The rarest tortoise on earth. Oryx 20: 35−39. Currylow, A. (2014): No refuge at the end of the earth: beating hustlers, poverty, and disease to save the Ploughshares. In: The Tortoise magazine, vol. 1 p. 28−37. New York, New York, USA, the Turtle Conservancy. Doak, D., Kareiva, P., Klepetka, B. (1994): Modeling population viability for the Desert Tortoise in the western Mojave Desert. Ecological Applications 4: 446−460. Goodman, S.M., Pidgeon, M., O'Connor, S. (1994): Mass mortality of Madagascar Radiated Tortoise caused by road construction. Oryx 28: 115−118. Hoogmoed, M.S., Vliet, K.A. (1985): Two reptiles among the 12 most threatened animals of the world. Amphibia-Reptilia 6: 101−115. Juvik, J., Andrianarivo, A., Blanc, C. (1981): The ecology and status of Geochelone yniphora: a Critically Endangered tortoise
487
Ploughshare Tortoise natural entrapment in northwestern Madagascar. Biological Conservation 19: 297−316. Kiester, A.R., Mandimbihasina, A.R., Lewis, R.E., Goode, E.V., Juvik, J.O., Young, R., Blanck, T. (2013): Conservation of the Angonoka (Ploughshare Tortoise), Astrochelys yniphora. Chelonian Research Monographs 6: 162−170. Mandimbihasina, A.R., Currylow, A.F.T. (2014): New data on the naturally-occurring maximum sizes attained by Ploughshare Tortoises (Astrochelys yniphora). Herpetology Notes 7: 685−688. Mandimbihasina, A.R., Woolaver, L. (2014): Astrochelys yniphora Ploughshare tortoise. In: Tortoises of the Western Indian Ocean, p. 279−298. Mandimbihasina, A.R., Woolaver, L., Gerlach, J. Ed. Rochdale, UK, Siri Scientific Press. Pedrono, M., Smith, L.L., Clobert, J., Massot, M., Sarrazin, F. (2004): Wild-captive metapopulation viability analysis. Biological Conservation 119: 463-473. Rhodin, A.G.J., Walde, A.D., Horne, B.D., Dijk, P.P.v., Blanck, T., Hudson, R. (2011): Turtles in Trouble: The world’s 25+ most endagered tortoises and freshwater turtles−2011. Turtle Conservation Coalition. 54 pp.
Riedle, J.D., Averill-Murray, R.C., Grandmaison, D.D. (2010): Seasonal variation in survivorship and mortality of Desert Tortoises in the Sonoran Desert, Arizona. Journal of Herpetology 44: 164−167. Rorabaugh, J. (2003): Apparent accidental death: Chuckwalla meets Agave. Sonoran Herpetologist 16: 44. Walker, R.C.J., Rafeliarisoa, T.H., Currylow, A.F., Rakotoniainae, J.C., Louis Jr., E.E. (2014): Short term monitoring reveals the rapid decline of southern Madagascar’s Critically Endangered tortoise species. Herpetological Journal 24: 193−196. Wilson, J.S., Topham, S. (2009): Gopherus agassizii (Desert Tortoise). Mortality. Herpetological Review 40: 335−336.
Accepted by Gonçalo Rosa
