When I drove to Florida recently, one of my target species to record was the Southern Toad. I hadn't really learned the call in advance but I figured I would recognize it when I heard it since I knew most of the other species in the state. On the way, we stopped one evening in southern Mississippi to do some herping and I heard a long trilling call. At first I thought it was an American Toad and recorded it without thinking. A few minutes later we found a toad on the road, but it was a Southern Toad. That's when I realized I was too far south for American Toads...so what was that call? I pulled up my Lang Elliott recording of US Anurans on my Ipod and listened. It was indeed, the Southern Toad. I had no idea they sounded like American Toads!
Actually, there are several species of similar looking Anaxyrus species in the Southeastern US; Fowler's Toad, American Toad, and Southern Toad.
Fowler's Toad (Anaxyrus fowleri) looks similar to the American Toad (Anaxyrus americanus) but is easily separated by call. I have dealt with those two species in a separate blog post. Southern Toad (Anaxyrus terrestris) is easily separated from American and Fowler's Toads by the enlarged posterior extensions on its cranial crests.
Where they do come near each other, the American Toad is found in the mountains and Southern Toad is found in the below the fall line in the Coastal Plain. But there are areas where both toads can be found in the same areas. Here is an approximate range map for the two species in the Southeastern US showing the possible areas of overlap (this map is not meant to be accurate county by county, just an approximation). Red represents the range of American Toad, yellow represents Southern Toad and the orange the possible zone of overlap.
Both species have a call that is a long high pitched trill.
Here is the American Toad (Anaxyrus americanus)
and here is the Southern Toad (Anaxyrus terrestris)
Looking at the spectra of the two calls, we see that the Southern Toad call is a noticeably higher in pitch than the American Toad. In this example we see the American Toad with a peak frequency of around 1900 Hz while the Southern Toad is visibly (and audibly) higher with a peak of 2350 Hz.
So although these toads barely overlap in range, their calls are similar enough sounding that in the zones of overlap, it might be worth listening carefully or recording the call just to be sure.
© Chris Harrison 2018