Correlation Between Individual Body Condition and Seasonal Activity in Buresch’s Crested Newt, Triturus ivanbureschi

Body condition is a standard measure of the individual fitness and health status in many animal species and is typically estimated by calculating the body condition indices (BCIs). The present study used capture/recapture data and the BCIs to test whether the activity (number of times an individual has been recaptured) of adult T. ivanbureschi was related to individual body condition. For three consecutive seasons, we set funnel traps in a temporary pond near Sofia, Bulgaria. A ventral pattern was used for individual identification, and the linear regression of lnMass/lnSVL was used for BCI calculation. The overall recapture rate for the population was 52.52%, with males recaptured more often than females. Activity and estimated population size varied across seasons. Body condition generally decreased towards the end of the aquatic phase in all years, with females consistently maintaining higher BCIs than males. There was no relationship between mean BCI per session and population activity for either sex, but individual BCI scores were correlated with individual activity, and this relationship was independent of both sex and temperature. The results suggest that winter activity may carry energetic costs later in the season and highlight potential sex-based differences in aquatic behavior.