Thank you for your thoughts. I live about 16 km. from the centre of Johannesburg, in a suburb called Rivonia, Sandton. There are a few known, small wetland areas around Johannesburg that support Bullfrogs, but most of these are being threatened by the inevitable development that is going on.

Are there any other sound recordings of different frog species on Frog Forum? If there are, I would be grateful for a link to them. The mystery continues, but I am enjoying my nameless frog - he was calling as I typed my first post last night.!