Hi, and thank you so much for your reply - I think that you have solved my query!

Since my first post, I have decided that the call I hear is definitely not that of a Bullfrog. I have just 'googled' the 3 Toad varities you mentioned, and found a sound clip for the Guttural Toad, and that is EXACTLY what this one in my garden sounds like - it is a loud, hollow, rattling, popping sound.

A website I found in Cape Town, calls it an 'aggressive invader' and one to get rid of?? I am quite distressed to have one living here! I have lived in Rietfontein Road, Rivonia since 1966 - have always had what I call 'ordinary little, green/brown garden frogs hopping about and calling on Summer evenings, HOWEVER, this Summer there have been no frogs at all. I put it down to the many Hadedas that feed here, and thought they had eaten all the froglets, but could it be that this wretched Toad has eliminated them??

Thanks again for you input.