Population demography of Oldham's leaf turtle (Cyclemys oldhamii) in protected and disturbed habitats in Thailand

This species is vulnerable to human impacts due to its life history traits, including delayed reproduction, delayed reproduction, and low fecundity. Freshwater turtle populations have undergone dramatic declines in recent decades due to collection for food, pet, and traditional medicine markets. A mark-recapture study was conducted at three sites in northeastern Thailand: a protected stream, a degraded stream, and human-constructed ponds. The study evaluated differences in survival, density, population structure, and sexual dimorphism between the sites. The results showed that survival was 12% lower and density was 35% lower in the constructed ponds compared to the protected stream. Size class structure was skewed towards smaller individuals at the constructed ponds, and both sites exhibited subadult-skewed age class structure. Sex ratios were not statistically different from 1:1 at either site, and did not differ between sites. The study suggests that collection for consumption or Buddhist prayer release locally, collection for illegal export from Thailand, predation by domestic dogs, and lower habitat quality may be responsible for the lower survival, lower densities, and skewed size class structure at the constructed ponds. The information gained from this study may contribute to a status assessment for C. oldhamii and development of conservation actions to protect populations in Thailand. Turtles exhibit life history traits that make their populations vulnerable to human impacts in their environments. Freshwater turtle species are characterized by delayed reproduction, delayed reproduction, and low fecundity, making them susceptible to anthropogenic impacts. These traits can lead populations into an extinction vortex from which they are unlikely to recover. Human activities have been associated with declines in freshwater turtle populations, including opening up protected areas for hikers, invasive activities such as sedimentation of aquatic habitats, predation by non-native predators, and direct removal of individuals for trade. Demographic traits may signal human-induced changes in populations, which could lead to declines over time. The demographic or ecological traits potentially shifted by human activities depend on the life history of the focal species and the particular type of perturbation. Asian turtle populations have been inordinately impacted by harvesting for markets, traditional Chinese medicine, and the international pet trade. The 'Asian turtle crisis' has resulted in 80% of Asian turtles being listed as threatened, with more than 50% being Endangered or Critically Endangered. For most species, there has been little research beyond the initial species description and taxonomic resolution on related species. Populations of many Asian turtle species have declined to such low levels that studying their ecology or population biology has become difficult. Quantifying the demographic structure of turtle populations is essential for understanding population trends and conservation needs, particularly in the context of rapid land use change in Southeast Asia. Despite some populations remaining in Southeast Asia, Asian leaf turtles (Cyclemys spp.) are of conservation concern. Three populations of Oldham's leaf turtle were studied to quantify the effects of human activities on survival, age class structure, size class structure, sex ratio, and degree of sexual dimorphism. The study tested hypotheses based on documented vulnerabilities of freshwater turtles to anthropogenic disturbance.