Seasonal variation in anuran diversity and activity in the Vredefort Dome conservation area

Abstract

On 14 July 2005 the Vredefort Dome was declared the 7th world Heritage Site of South Africa. Today it is generally accepted to be the oldest and largest meteorite impact site in the world. It was formed about 2020 million years ago when a meteorite as big as Table Mountain struck the earth at great speed, creating a crater of about 250 km in diameter and 40 km deep. Today, only the eroded remnants are visible northwest of the impact site. The geology and geography of the area has been studied in great detail, but we know relatively little about the ecology and animal diversity of the Vredefort Dome area. Of the chordates, the amphibians are the least-known group of organisms in the area. The aims of the present study were to determine the species diversity, seasonal activity patterns, breeding behaviours, interaction of amphibians, and to verify the status of the amphibian chytrid, Batrachochytrium dentrobatidis in the Vredefort Dome area. Historical data collected during the South African Frog Atlas Project and other surveys indicated that the following species were present in this area: Afrana angolensis, A. fuscigula, Breviceps adspersus, Bufo gutturalis, B. rangeri, B. poweri, Cacosternum boettgeri, Kassina senegalensis, Phrynobatrachus natalensis, Pyxicephalus adspersus, Schismaderma carens, Semnodactylus wealii, Strongylopus fasciatus, Tomopterna cryptotis and Xenopus laevis. As the study area covers only two quarter-degree grid cells it was decided to conduct this study on a finer scale to ensure a better resolution. Frogs were identified on the male chorus during the breeding season and on visual encounters. Tadpoles were also used to identify anuran species and to determine the presence of the amphibian chytrid. This monitoring stretched over a period of one year. The following species were identified during the monitoring period: Afrana angolensis, A. fuscigula, Breviceps adspersus, Bufo gutturalis, B. rangeri, B. poweri, Cacosternum boettgeri, Kassina senegalensis, Schismaderma carens, Strongylopus fasciatus, Tomopterna cryptotis, T. natalensis and Xenopus laevis. Chytridiomycosis was identified in Afrana angolensis during the dry months of August, September, October and November.