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

Simple Summary Habitat loss and nest predation significantly threaten European pond turtle (Emys orbicularis) populations. To reveal predation pressure in a protected area (Kis-Balaton marshland, Hungary) we conducted an artificial nests experiment. We used real nests which had been predated, and near each of them we created a new artificial nest. In each nest hole we put one quail egg, one plasticine egg and turtle egg shells and then covered them and sprayed the surface with water-diluted turtle urine. The majority of the nests were depredated in the first three nights, mostly by red foxes (Vulpes vulpes), confirmed by the bite marks preserved on the plasticine eggs, by footprints and excrements found near the nests and by camera recordings. Daily survival rates of quail eggs in artificial nests established in both real and in new nests were similar, suggesting that estimates obtained with artificial nests reflect the degree of predation pressure on real nests. Scattered nests had a lower survival rate than partly scattered and partly linear or only linearly arranged nests. We proved that spraying the nests with diluted turtle urine and marking them with a flag did not affect their survival. The results support turtle nest protection and selective predator control. Nest predation significantly impacts the population decline of the long-living European pond turtle (Emys orbicularis). Kis-Balaton is one of the most important habitats of this species in Hungary, and in May 2017 more than 400 damaged nests were counted. To reveal predation pressure, we conducted a study with artificial nests on three sites in this area. On each site, we used 11 depredated real nests, and near each of them, we created new artificial nests; then in every nest we put one quail egg, one plasticine egg and several turtle egg shells. After that, we sprayed the smoothed surface of the covered holes with water-diluted turtle urine, imitating the turtle's behaviour. Already in the first three nights, 94% of all nests were depredated by the red fox (Vulpes vulpes) and in one case by the European badger (Meles meles), which was confirmed by the bite marks preserved on the plasticine eggs, by the footprints and excrements found near the nests, as well as by camera recordings. Only 6% of the nests survived during the three weeks of our study. Daily survival rates of quail eggs in artificial nests established in both real (damaged) and in new nests were similar, suggesting that estimates obtained with artificial nests reflect the degree of predation pressure on real nests. On the site where the nests were scattered, their daily survival rate (33%) was significantly lower than on the sites where their arrangement was partly scattered, partly linear (83%), or only linear (76%). On two additional sites, by using simulated turtle nests we showed that spraying the nests with diluted turtle urine and marking them with a flag did not affect their survival, although further methodological testing is needed. The information obtained with artificial nests enables the organization of the protection of the nests of the European pond turtle and selective predator control.