Résumé
1. Most studies on the effect of drought on the biodiversity of freshwater systems have focussed on natural droughts. We sought to assess the effects of artificial drainage on the population dynamics of the European pond turtle (Emys orbicularis). We investigated whether the probability of survival and emigration/immigration was affected by short-term drawdown (for a few months over winter) or long-term habitat drainage (a full year of drying out) in this long-lived species of low dispersal ability.
2. The study was replicated in two different areas using a Capture-Recapture monitoring programme over 5 years. In the two areas, we marked 1412 and 282 individuals, respectively. Short-term drawdown had no impact on the vital rates of this species, while long-term drainage promoted greater mobility among the ponds in both areas. This increase in movement might reduce survival, due to road mortality, or result in turtles leaving the study area.
3. Moreover, as the transition probability between ponds was higher when ponds were close together and directly connected, for instance by a ditch, the construction and maintenance of ditches might reduce the effects of drainage. To implement effective conservation plans, studies that aim to assess the effect of human disturbance should monitor population dynamics and vital rates to allow a more complete picture of the real impacts.