The American Bullfrog (Lithobates catesbeianus) is probably one of the best known anurans in North America. It was a wide range across North America, as a native in some areas and an introduced pest in others.
It's call has been various described as resonant "rah-uhm" or as "jug-o-rum". The general sound of its call is fairly consistent and different than other native species although there is some variation in the type of call, even within a single pond.
Bullfrogs typically call from the shallow edge of a pond. They are notoriously shy about calling compared to other species and I have had a hard time getting a photo of their vocal sac. You can just see it extended in this individual.
All of these Bullfrogs were photographed and recorded at a single pond at Aransas National Wildlife Refuge, Texas.
The basic call is a two part "rah-uhm" call with the first pitch higher than the second -
Although there are variations that have more syllable, some of which can increase in pitch -
© Chris Harrison 2012