Demographic Evidence of Illegal Harvesting of an Endangered Asian Turtle

Abstract

Harvesting pressure on Asian freshwater turtles is severe, and dramatic population declines of these turtles are being driven by unsustainable collection for food markets, pet trade, and traditional Chinese medicine. Populations of big-headed turtle (Platysternon megacephalum) have declined substantially across its distribution, particularly in China, because of overcollection. To understand the effects of chronic harvesting pressure on big-headed turtle populations, we examined the effects of illegal harvesting on the demography of populations in Hong Kong, where some populations still exist. We used mark-recapture methods to compare demographic characteristics between sites with harvesting histories and one site in a fully protected area. Sites with a history of illegal turtle harvesting were characterized by the absence of large adults and skewed ratios of juveniles to adults, which may have negative implications for the long-term viability of populations. These sites also had lower densities of adults and smaller adult body sizes than the protected site. Given that populations throughout most of the species' range are heavily harvested and individuals are increasingly difficult to find in mainland China, the illegal collection of turtles from populations in Hong Kong may increase over time. Long-term monitoring of populations is essential to track effects of illegal collection, and increased patrolling is needed to help control illegal harvesting of populations, particularly in national parks. Because few, if any, other completely protected populations remain in the region, our data on an unharvested population of big-headed turtles serve as an important reference for assessing the negative consequences of harvesting on populations of stream turtles. Evidencia Demográfica de la Captura Ilegal de una Tortuga Asiática en Peligro.

Diet of the endangered big-headed turtlePlatysternon megacephalum

“…In Hong Kong, Platysternon megacephalum is protected under the Wild Animals Protection Ordinance Cap. 170, which prohibits any collection or use, but turtle populations in protected areas have been subjected to illegal harvesting (Sung, Karraker & Hau, 2013). …”

“…Turtles were captured as part of a mark-recapture study (Sung, Karraker & Hau, 2013) carried out between September 2009 and June 2011, which included wet (April–September) and dry (October–March) seasons. We collected basic morphometric data on captured turtles, including straight-line carapace length (CL) using calipers, and body mass using a spring scale.…”

“…Populations of Platysternon megacephalum are declining at unprecedented rates across its distribution (Hendrie, 2000; Stuart & Timmins, 2000; Sung, Karraker & Hau, 2013; Tana et al, 2000; Wan et al, 2015), and thus it was recently proposed that its status be upgraded from Endangered to Critically Endangered (Horne, Poole & Walde, 2012). There is no evidence that harvesting is abating.…”

Conservation Status of Freshwater Turtles in Hainan Island, China: Interviews and Field Surveys at Yinggeling Nature Reserve

“…We installed traps made of wire mesh, measuring 45 3 20 3 15 cm, on the forest floor and placed partially submerged traps on the edge of streams. Traps were baited with salted fish, meat, or cattle viscera and checked at least every 3 d. The trap design and bait choice have proven to be effective throughout southern China (Gong et al 2005b;Sung et al 2013).…”

“…Identification of key conservation areas with the highest turtle diversity or abundance is crucial to maximize the effectiveness of patrols and, thus, can be an effective measure to tackle illegal turtle hunting (Sung et al 2013). In situ conservation actions, including setting up protected area with effective enforcement, have been recommended as crucial measures for conservation of freshwater turtles (Horne et al 2012).…”