This species has a huge vocal sac that comes out from the front of the throat but inflates to almost 50% of the toad's total size. The call produced by this large vocal sac is probably best described as a shrill trilling.
This is the recording of the male seen in the photo (Karnes County, Texas)
The sonogram looks like this. This sonogram just shows two calls from the above recording.
A chorus of these frogs can make an extraordinary racket. Here's a large chorus from Wilson County, Texas in June of 2009.
Here a video of an individual calling in Duval County, Texas (along with a loud chorus of Sheep Frogs (Hypopachus variolosus)).
and another short video of one calling from Frio County, Texas.
© Chris Harrison 2012