HABITAT DISTRIBUTION AND VOCAL ACTIVITY OF THE MARSH FROG (PELOPHYLAX RIDIBUNDUS), THE EUROPEAN GREEN TOAD (PSEUDEPIDALEA VIRIDIS) AND THE EASTERN SPADEFOOT (PELOBATES SYRIACUS) (ANURA: RANIDAE, BUFONIDAE, PELOBATIDAE) IN THE PROTECTED AREA OF RUPITE
Natural & Mathematical science
The habitat distribution and vocal activity of three anuran species were studied in three localities in the protected area of Rupite. The heavy-built terrestrial species P. viridis and P.syriacus were found only in ponds, while the semi-aquatic P. ridibundus also occupied flowing waters. We observed increased nocturnal activity in the area around the thermal springs. This probably was due to the higher and relatively constant water temperature. We did not observe any activity of P.syriacus,
... of P.syriacus, however, in one pond we found numerous dead specimens. The reasons for the observed ecological and behavioral characteristics are discussed. INTRODUCTION Nearly every aspect of amphibian physiology and behavior is affected by temperature. While locomotion in some species is relatively temperature independent over a narrow range of temperatures , aerobic metabolism is temperature dependent in all amphibians and generally increases in a linear fashion as temperature increases . Body temperature is close to that of the immediate surroundings, especially the substrate. The amount of metabolic heat produced is so small that it is lost to the environment . In warm environments most amphibian behavior seems to be associated with maintaining low body temperatures, but cryptic and nocturnal is likely a response to problems of water economy than to temperature . Amphibians as a group have a wide range of thermal tolerances. However, preferred body temperatures usually are nearer the upper than the lower extremes of temperatures tolerated [3, 4]. By habits of postmetamorphic stages outside the breeding season  divides the amphibian species into terrestrial and semi-aquatic. Despite the existence of some papers  the scientific data on the ecology of Bulgarian amphibians is still insufficient. This research aimed to establish the level of activity and the character of habitat distribution of three anuran species-the marsh frog Pelophylax ridibundus (Pallas 1771), the eastern spadefoot Pelobates syriacus (Boettger 1889) and the European green toad Pseudepidalea viridis (Laurenti 1768)-in the beginning of their breeding seasons in an area near the village of Rupite. All three are included in the Biodiversity Act-the marsh frog in appendix IV and the green toad and the eastern spadefoot in app. III, and the BERN convention-the marsh frog in app. III, the green toad and the eastern spadefoot in app. II. The green toad and the eastern spadefoot are terrestrial species with cryptic/nocturnal activity, while the marsh frog is a semi-aquatic species with twenty-four-hour activity . Due to the fact that no terrestrial species lays its eggs in ponds where the marsh frog is by all means absent, the former two species could come in contact with the marsh frog during the breeding season, when they enter ponds to lay their eggs . The chosen area included both ponds and slow-flowing canals formed by thermal springs. We expected a higher level of activity near the thermal springs compared to other localities.