Bibliography - Nine Abstracts on the Impact of Collecting Herps on Wild Populations

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Cowboy_Ken

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Courtesy Shane de Solla,
Ecotoxicologist
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2a) Commercial harvesting of giant lizards: The biology of water monitors Varanus salvator in southern Sumatra
Biological Conservation
Volume 77, Issue 2-3, 1996, Pages 125-134
Shine, R. , Harlow, P.S., Keogh, J.S., Boeadi
Contact Rick Shine [email protected]
Abstract

The Asian water monitor Varanus salvator is the second-largest lizard species in the world (to > 1 m SVL, 2.5 m total, 20 kg), and is heavily exploited (> 1 million skins per annum). In the course of three trips between August 1993 and April 1995, we gathered information on 166 water monitors captured in southern Sumatra for the commercial skin trade. Relatively equal numbers of males and females were captured, but the males were almost all adults whereas half of the females were juveniles. Sex ratios and body sizes did not vary significantly among the three trips. Males grow larger than females, but the largest animals are not used in the leather trade. Males mature at around 40 cm SVL (= 1 m total, 1 kg), and females at around 50 cm. Maturation thus occurs at a small proportion of maximum size, as is typical for large species of reptiles. Adult males are more heavy-bodied than females, and have longer tails, but fat stores did not differ between the sexes. Prey items included crustaceans, rats and other varanids, but most lizards were kept for so long prior to slaughter that the stomach was empty of food. All adult-size males had active gonads, but testes were larger in April than in October. All adult females in the August and April samples were reproductively active, but less activity was evident in October. The egg-laying season extends from April to October. The egg-laying season extends from April to October (at least), and most female water monitors in southern Sumatra produce multiple clutches each year. Larger females began to breed earlier in the year than do smaller animals. Clutch sizes ranged from five to 22, and were positively correlated with maternal body size. We measured stretched and dried skins from processed lizards to establish a predictive equation linking lizard SVL to skin width. The persistence of water monitors in southern Sumatra, despite intense harvesting, reflects the large area of suitable habitat with low human densities, combined with the monitors' ecological flexibility (in habitat and diets), their high reproductive rate (early maturation and frequent reproduction), and (perhaps) the concentration of commercial harvesting on adult males. At current levels, the commercial trade may extirpate varanids from local areas but will not drive the species to extinction.

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2b) Collectors endanger Australia's most threatened snake, the broad-headed snake Hoplocephalus bungaroides
Webb, J.K. , Brook, B.W., Shine, R.
Oryx Vol 36 No 2 April 2002
Jonathan K. Webb1 (Corresponding author), Barry W. Brook, Key Centre for
Tropical Wildlife Management, Northern Territory University, Darwin 0909 NT, Australia. E-mail: [email protected]
Richard Shine School of Biological Sciences, The University of Sydney, NSW 2006,,
Present address: School of Biological Sciences, The University of Sydney, NSW, Australia.

Abstract

The collection of reptiles for the pet trade is often cited as a potential problem for threatened species, but quantitative data on the effects of this trade on wild populations are lacking. In south-eastern Australia the decline of the threatened broad-headed snake Hoplocephalus bungaroides has been blamed on habitat destruction and the collection of snakes for pets, but there was little evidence to support the latter hypothesis. During 1992-2000 we studied one of the last extant southern populations of broad-headed snakes in Morton National Park, New South Wales, where <600 individuals remain on an isolated plateau. Analysis of 9 years of mark-recapture data reveal that the activities of snake collectors seriously endanger the viability of this species. The study population of H. bungaroides was stable over 1992-1996, but declined dramatically in 1997, coincident with evidence of illegal collecting, possibly stimulated by a government amnesty that allowed pet owners to obtain permits for illegally held reptiles. Survivorship analyses revealed that 85% of adult females disappeared from the population in 1997. There was no such effect on male survivorship, suggesting that snake collectors selectively removed adult females, which are the largest snakes in the population. Humans caused significant damage to fragile rock outcrops in three of the 9 years of the study, and a second bout of habitat disturbance in 1999 coincided with a second decline in the H. bungaroides population. We recommend that locked gates be placed on fire trails to protect existing populations of broad-headed snakes

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2c) Reticulated pythons in Sumatra: biology, harvesting and sustainability
Biological Conservation 87 (1999) 349±357
Richard Shine a,*, Ambariyanto a,1, Peter S. Harlowa, Mumpunib
aSchool of Biological Sciences A08, The University of Sydney, Sydney, N.S.W. 2006, Australia
1 Present address: Dipenegoro University, JI. Imam Bardjo SH,
Semarang, Indonesia.
bCentre for Research in Biology, Museum of Zoology, LIPI, Bogor 16122, Indonesia
* Corresponding author. Fax: +61-2-9351-5609;
e-mail: [email protected]

Abstract

Hundreds of thousands of giant snakes (Python reticulatus) are taken from the wild to be killed for their skins each year, raising doubts about the longterm sustainability of this offtake. We visited four locations in northern Sumatra (Medan, Seisuka, Rantauprapat and Cikampak) at four times of year and gathered information on the sizes, sexes, reproductive status and food habits of 784 slaughtered pythons. Pythons in northern Sumatra mature at larger body sizes than do those studied previously in southern Sumatra (Palembang). Their seasonal timing of reproduction is shifted appreciably, presumably because the two areas lie on opposite sides of the equator. The slaughtered animals are mainly adult males and adult plus juvenile females. Females attain larger sizes than males, but very large females are rarely captured. This bias may reflect size-related shifts in habitat selection; smaller snakes (including adult males of all sizes, and recently-matured females) feed primarily on commensal rats and hence are abundant in disturbed (agricultural and village) habitats. Female pythons produce large clutches (mean = 24.2) of large eggs (mass > 250 g), but reproduce only once every 2 to 4 years. The apparent ability of reticulated python populations to withstand high levels of off take may reflect their demography (rapid growth rates, early maturation, high fecundity), their flexibility in diets and habitat use, and their ability to evade detection (because neither foraging nor thermoregulation require extensive movements).

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2d) Demonstrating decline of an iconic species under sustained indigenous harvest - The pig-nosed turtle (Carettochelys insculpta) in Papua New Guinea
Biological Conservation (2011) Volume: 144, Issue: 9, Publisher: Elsevier Ltd, Pages: 2282-2288
Carla C Eisemberg a, , Mark Rose b, M., Benedict Yaru, c., Arthur Georges, a
Contact Carla C. Eisenberg ([email protected])
a Institute for Applied Ecology, University of Canberra, ACT 2601, Australia
b Flora & Fauna International, Jupiter House, 4th Floor, Station Road, Cambridge, CB1 2JD, UK
c Oil Search Ltd., GPO Box 2442, Sydney, NSW 2001, Australia

Abstract

Papua New Guinea has astonishing biological and cultural diversity which, coupled with a strong community reliance on the land and its biota for subsistence, add complexity to monitoring and conservation and in particular, the demonstration of declines in wildlife populations. Many species of concern are long-lived which provides additional challenges for conservation. We provide, for the first time, concrete evidence of a substantive decline in populations of the pig-nosed turtle (Carettochelys insculpta); an important source of protein for local communities. Our study combined matched village and market surveys separated by 30. years, trends in nesting female size, and assessment of levels and efficacy of harvest, each of which was an essential ingredient to making a definitive assessment of population trends. Opportunities for an effective response by local communities to these declines needs to consider both conservation and fisheries perspectives because local communities consider the turtle a food resource, whereas the broader global community views it as a high priority for conservation. Our study in the Kikori region is representative of harvest regimes in most rivers within the range of the species in Papua New Guinea, and provides lessons for conservation of many other wildlife species subject to harvest.

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2e) Indigenous harvest, exotic pig predation and local persistence of a long-lived vertebrate: Managing a tropical freshwater turtle for sustainability and conservation
Journal of Applied Ecology Volume 45, Issue 1, pages 52–62, February 2008
Fordham, D.A., Georges, A. , Brook, B.W.
1 Institute for Applied Ecology, University of Canberra, ACT 2601, Australia;
2 School for Environmental Research, Institute of Advanced Studies, Charles Darwin University, Darwin NT 0909, Australia; and
3 Research Institute for Climate Change and Sustainability, School of Earth & Environmental Sciences, University of Adelaide, South Australia 5005, Australia
* Correspondence author. E-mail: [email protected]


Abstract

1. Until recently, the northern snake-necked turtle (Chelodina rugosa Ogilby, 1890) provided a seasonal source of protein for indigenous communities in tropical northern Australia. Today, feral pigs (Sus scrofa Linnaeus, 1758) exert a heavy predation pressure on C. rugosa, compromising subsistence harvest rates and threatening local persistence. 2. We investigated the influence of pig predation and harvest (subsistence and commercial) on C. rugosa persistence at discrete water holes using a stage-based matrix population model. Vital rates varied with wet season rainfall, pig predation and harvest. In addition, hatchling survival was density-dependent. 3. We show that field-based estimates of pig-related turtle mortality exceed levels that can be offset by increased hatchling survival, leading to predictions of rapid population decline and certain elimination of affected populations within 50 years. 4. Conversely, in the absence of pigs, compensatory increases in hatchling survival were sufficient to allow an annual harvest of up to 20% of subadult and adult C. rugosa without causing extirpation or substantial population suppression. 5. Synthesis and applications. This demographic modelling shows that periodic local culling of pigs, fencing of wetlands to exclude predators, and hatchling supplementation to offset losses from predation are all viable management strategies for ensuring ongoing turtle harvests. Such demonstrations of the potential resilience of long-lived vertebrates under a properly managed harvest regime is important to convince natural resource agencies that conservation management for long-term viability need not exclude some degree of consumptive use. These findings are broadly relevant to applied ecology, providing important implications for the management of wildlife species subject to competing ecological pressures, such as subsistence and commercial harvesting and predation by invasive species.

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2f) A 20-Yr Study Documenting the Relationship Between Turtle Decline and Human Recreation.
Garber, Steven D., and Joanna Burger. 1995.
Ecological Applications 5:1151â•„1162.
(Contact was not supplied by publisher on net, but Ms. Burger I think is still at Rutgers University, NJ)

This study documents the detrimental effects of human recreation on the North American wood turtle (Clemmys insculpta) in Connecticut. We chronicled the dynamics of two allopatric wood turtle populations in a protected southern New England wildlife reserve for 20 yr (1974-1993). Both wood turtle populations were reproductively isolated from one another, physically separated â≈√100 yr ago when a 1.5 km long human-made pond was constructed. We conducted a mark-and-recapture study on a 1000-ha section of a protected watershed in south-central Connecticut (New Haven County). During this study we monitored 133 different wood turtles, observing them a total of 1176 times. Human and wood turtle demographics were recorded throughout this period. The data support the following conclusions: (1) following a period of apparent stability, two populations of wood turtles declined; (2) the declines were more or less synchronous in both populations; (3) the beginning of each decline corresponded to the opening of the habitat for recreation; (4) an increase in mean turtle age suggests a failure of recruitment; however, (5) a simultaneous reduction in numbers of adult females suggests that the failure of recruitment alone is not sufficient to explain the declines. Throughout our study the size of the forest remained the same, road building was restricted, and the quality of the air and water were constant. The wood turtle populations remained stable when people were denied access to the property. When this area was opened to human recreation (hiking, fishing) the two discrete wood turtle populations declined steadily; the total number of turtles in both populations declined by 100% in 10 yr. As wilderness areas become mixed-use recreation areas, wood turtle populations may suffer. We conclude that without proper management, the increasing recreational use of parks, reservoirs, and wildlife reserves will adversely affect the long-term survival of the North American wood turtle.

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2g) Ecological attributes of two commercially-harvested python species in northern Sumatra
Richard Shine, Ambariyanto, Peter S. Harlow and Mumpuni
Journal of Herpetology
Vol. 33, No. 2 (Jun., 1999), pp. 249-257
Contact - Rick Shine [email protected]

Abstract

Examination of specimens collected for the international leather trade provided data on two species of large, heavy-bodied snakes: blood pythons (Python brongersmai) from northeastern Sumatra and short-tailed pythons (P. curtus) from northwestern Sumatra. Measurement and dissection of 2063 P. brongersmai and 181 P. curtus revealed broad interspecific similarities in morphology (size, shape, sexual dimorphism), food habits (feeding frequencies, dietary composition) and reproductive output (reproductive frequencies, egg sizes, and clutch sizes). Females of both species attain larger sizes than males, mature at larger sizes, and contain larger abdominal fatbodies. Python curtus is more heavy-bodied and longer-tailed than P. brongersmai, and more heavily infested with gut parasites. Both species feed almost exclusively on commensal rodents. Feeding rates increase with body size, and vary seasonally. Reproduction is highly seasonal. Adult females reproduce biennially, producing aby n average clutch of 12 to 16 large (mean = 83 to 90 g) eggs. The data also enable us to comment on the sustainability of the existing commercial trade, which is based mainly on adult males, and adult plus juvenile females. Anthropogenic habitat modification (especially, the establishment of oil-palm plantations) has increased the abundance of these taxa. Although neither species is likely to be extirpated by current levels of offtake, we need additional information to evaluate long-term sustainability of the commercial industry based on these snakes.
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2h) Exurban sprawl increases the extinction probability of a threatened tortoise due to pet collections
Ecological Modelling. Volume 245, 24 October 2012, Pages 19-30
Irene Péreza, b, , ,
Alicia Tenzab,
José Daniel Anadónb, c,
Julia Martínez-Fernándezb, d,
Andrés Pedreñoe,
Andrés Giménezb
a Center for the Study of Institutional Diversity, Arizona State University, Tempe, AZ, USA
b Departamento de Biología Aplicada, Ecología, Universidad Miguel Hernández, Elche, Alicante, Spain
c Department of Conservation Biology, Estación Biológica de Doñana (EBD-CSIC), Sevilla, Spain
d Departamento de Ecología e Hidrología, Universidad de Murcia, Espinardo, Murcia, Spain
e Departamento de Sociología y Política Social, Univeridad de Murcia, Espinardo, Murcia, Spain
Contact -Irene Perez - [email protected]

Abstract

Human behavior is an important factor in understanding the impact of exurban sprawl (i.e. low-density rural home development) on native species. We studied the long-term effect of pet collection on populations of the threatened spur-thighed tortoise by residents of exurban areas in southeastern Spain. We built a system dynamic model using authors' own data and bibliographic data about tortoise population dynamics, the housing development dynamics, and the behavior of local residents toward this species. The model includes two submodels (spur-thighed population dynamics and households dynamics) interconnected through a tortoise collection submodel. Simulations showed that exurban intensity (i.e. size of a housing development) is essential in determining the intensity and speed of tortoise population decrease. Populations may become extinct due to collection in areas around medium to large housing developments (above 650 houses). Low housing development causes a considerable reduction of original population levels (more than 14%). Environmental education program by itself, with the aim of reducing the willingness of new residents to keep tortoises in captivity, does not seem very effective. The quality and the speed with which the educational program is initialized are key factors in determining the effectiveness of the educational program. The scenarios simulation results suggest that the integration of policies of strong development constraints and educational programs are the most effective way in reducing the impact of exurban development on tortoise populations.

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2i) Non-commercial collection of spur-thighed tortoises (Testudo graeca graeca): a cultural problem in southeast Spain.
Biological Conservation 118 (2004) 175–181 Irene Pérez, Andrés Giménez, José Antonio Sánchez-Zapata, José Daniel Anadón, Marcelo Martı́nez, Miguel Ángel Esteve. 2004.
Contact -Irene Perez - [email protected]

Abstract

Collecting tortoises for the pet trade is one of the factors threatening species of Testudo in the Mediterranean area. The collection of Testudo graeca graeca for pets is described in southeast Spain, where the main European population of this subspecies coincides with an area where keeping tortoises in captivity is a long-established custom. This present paper, based on inquiries made to children, reveals that this practice continues to be a common activity, and estimates a captive population in the order of tens of thousand of tortoises. Tortoises are collected as a result of chance encounters with wild animals by local inhabitants, and without any commercial objectives. The captive breeding and the release of tortoises without any institutional control is also common. These activities could be an important threat for the species. Implications for conservation are discussed and a critical review of the conservation strategies developed in relation to this threat (trade control and re-introduction programmes) are presented. We suggest that environmental education programmes are necessary to reduce casual collection and to change the social perception of tortoises as pets.
 
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