Fine scale behaviour and time-budget in the cryptic ectotherm European pond turtle Emys orbicularis

Abstract

For ectotherms, behaviour and associated energetic costs are directly related to thermal conditions. In the present context of global change, estimating time-budget for these species is relevant to assess and predict their capacity to adapt to near future. We tested the hypothesis that in ectotherms where reproduction is highly energy consuming, energy expenditure should vary throughout the breeding season with a maximum around nesting events. To test this hypothesis, we assessed the fine-scale behaviour, time-budget and estimated energetic costs in eight adult female European pond turtles Emys orbicularis equipped with data-loggers recording ambient temperature, pressure, light and the animals’ 3-axis acceleration. Deployments occurred over four months throughout the nesting season 2017 in semi-natural captive conditions in Alsace, France. All study turtles showed a clear daily pattern over the 24h cycle, with four distinct phases (referred to as Night, Morning, Midday and Evening), associated with different behaviours and activity levels. Before oviposition, turtles were mostly active during Morning, and activity was positively driven by ambient temperature. Activity levels doubled during the nesting period, mostly due to the increased activity in the Evening, when nesting events occurred. Throughout the active season, basking occurrence at Midday was related to air temperature but cloud coverage was an even more important factor. Our results are a first step in predicting the seasonal time and energy budgets of the European pond turtle, and demonstrate the usefulness of animal-borne accelerometers to study free living freshwater turtles over extended periods of time.

Developing a classification system to assign activity states to two species of freshwater turtles

“…Our results demonstrate high accuracy in classifying simple activity states as well as cross-species transferability of classification models among closely-related species in similar environments. Our research adds to other accelerometer-based behavioural identification studies, such as those by Marchand et al [ 52 ] and Lagarde et al [ 53 ], which describe fine-scaled behaviour in European pond turtle ( Emys orbicularis ) and Greek tortoises ( Testudo graeco ), respectively. Our research expands on these studies by characterising activity in two species of free-ranging turtles in their wild, native environment, which may be more representative of and transferable to real-life behavioural data collected by many researchers.…”

“…Even though in our study system differences in threshold values between species due to turtle body shapes and sizes did not impact transferability of classification models between species, our findings highlight the need for careful placement of sensors, especially where accurate separation between aquatic and terrestrial activity is a high priority. Arguably, attaching the device on the top of the carapace would produce more accurate sensor readings [ 52 ], and could ultimately improve classification performance. However, this option would likely increase the risk of device loss (A. Auge, unpubl.).…”

“…Our study provides a robust framework for rigorously testing the suitability of accelerometers for behavioural research in ecology. We conclude that accelerometers and other bio-logging tools hold much promise for characterising activity levels in free-ranging animals as well as developing behavioural profiles of cryptic and elusive species [ 22 , 52 , 63 ]. Accordingly, with proper validation measures such as those outlined herein, we expect accelerometry to become increasingly valuable as a tool for tracking animal behaviour across a variety of research and conservation or management contexts [ 64 ].…”

European Pond Turtle (Emys orbicularis) Nest Predation: A Study with Artificial Nests

“…It is possible that most of the nests which remained intact, were made by turtles at the beginning of the egg-laying period when the predators had not yet started to search for nests. The nesting period is a turning point in turtle activity, it is more limited to the noon and evening hours and does not show temperature dependence [ 58 ]. Before egg-laying, their activity is greatest in the morning due to food acquisition and linearly follow the temperature change.…”

“…Before egg-laying, their activity is greatest in the morning due to food acquisition and linearly follow the temperature change. During egg-laying, their activity has two peaks, as they dig nests in the evening [ 58 ]. In this period, changing from an aquatic to a terrestrial environment [ 59 ] can be a significant signal for predators, which presumably start searching for nests based on the change in the turtles’ daily activity.…”