Nest site selection and fidelity of European pond turtle (Emys orbicularis) population of Babat Valley (Gödöllő, Hungary)

Abstract

The conservation of aquatic and semiaquatic turtles requires knowledge of the area and vegetation structure of habitat used for nesting, and nesting migration route. We aimed to survey the effects of habitat features to the nest site selection, nesting success, and test the possibility of nest site fidelity. Our study was carried out at 10 different nesting areas, with special emphasis on data from returning females in a pond system in Hungary between 2014 and 2017. Most nesting attempts were found in closed sand steppes, uncharacteristic dry and semi-dry grasslands habitat patches. The principal component analysis (PCA) showed that increased sandy soil cover, sunlight and slope were important variables in nest site choice. The increasing PCA first axis score significantly increased the chance of an emergence. The degradation of open steppe vegetation, occurrence of weeds, invasive and disturbance tolerant species have a negative effect on the selection of nest sites. We observed that 96.55% of nests were located within 20 m south of a pine forest at preferred nest site at pond 5, which provided the right incubation temperature through partial shading. The returning females nested significantly closer to the northern pine forest than the single clutch females. Most probably the returning females already has the necessary experience to select the right nesting site. The individually marked females did not choose new nesting areas during the monitored years which suggests nesting area fidelity, but we did not find nest site fidelity. The maintenance of mosaic habitat structure, slowing down the succession process at the nesting area should be basic priorities in European pond turtle conservation programs. We suggested a spatial and temporal scheduling of land management and agricultural work to the local farmers. If the actual nest site is in an agricultural area, all work should be avoided throughout the year. Agricultural machinery should avoid the migration routes of adult turtles and emerged hatchlings during the concerned period. Under strong predation pressure, predator control should be carried out, and use nest protection.