Movement ecology, animal personalities, and the conservation of endangered freshwater turtles

Abstract

Globally, freshwater turtles represent one of the most threatened vertebrate groups, with many populations experiencing significant declines due to a multitude of human-induced rapid environmental changes. Understanding species-specific ecology and developing tailored conservation strategies are paramount to safeguarding the long-term persistence of these species and the proper functioning of ecosystems. By integrating advanced biologging technologies with robust analytical frameworks, this thesis provides detailed insights into animal movements and behaviors in two sympatric species of freshwater turtles in Hong Kong: the Beale’s eyed turtle (Sacalia bealei) and the big-headed turtle (Platysternon megacephalum). Through biotelemetry, I characterized the spatial behaviors and habitat use in a population of S. bealei. I demonstrated that both home range sizes and displacement distances vary substantially among reproductive classes, and in response to changing seasonal environmental conditions. Specifically, as influenced by differing reproductive roles, male exhibits larger home range and greater displacement distance than female. Analyses of habitat and microhabitat uses demonstrated a strong dependence on aquatic environments in S. bealei, with specific preferences for deep pools interspersed between repeating sequences of riffles and pools. S. bealei preferentially selects spatial elements that likely confer concealment advantages. These selections demonstrate behavioral flexibility in response to changing seasonal environmental conditions. Through the development of an accelerometer tailored to small- to medium-sized animals, I quantified activity profiles of P. megacephalum. This approach provides a numerical quantification of activity budgets, suggesting generally low activity rates across individuals of P. megacephalum. The species exhibits different activity profiles between sexes, with males demonstrating peak activity early in the day and females showing crepuscular activity around dawn and dusk. This research further illuminates the positive influences of temperature and precipitation on the time activity budgets of P. megacephalum, with possible ramifications for future climatic scenarios. Using an individualistic perspective on animal behaviors, I examined how poaching may unevenly influence the behavioral characteristics of wild populations of freshwater turtles. Through a series of standardized behavioral tests, I explored animal personalities in wild populations of S. bealei. Leveraging recent advances in computer vision models, I presented a methodological approach to collect behavioral data from freshwater turtles in a semi-automatic fashion. The results demonstrated that S. bealei presents with personality traits along both the bold-shy and exploration-avoidance continuums. Contrary to expectations, boldness and exploration do not explain trappability in S. bealei. Instead, the lack of clear links between animal personality and trappability challenges a common view on sampling bias in animal behavioral research. By weaving together the threads of animal movement and animal personality, my thesis fosters a holistic understanding of the intricate connections that shape the movement and behaviors of two endangered freshwater turtles within the movement ecology framework. Furthermore, by advancing our understanding of Chelonian ecology and their resilience to rapidly changing environmental conditions, this study provides implications for developing effective conservation strategies that consider the influences of various intrinsic and abiotic factors on space use and activity budgets across the two species.