Excerpt from the 1926 History of the Okefenokee Swamp by AS McQueen and Hamp Mizell:
“The alligators, especially at mating season, keep in touch with each other by ‘bellowing’ which sounds very much like a bull, except the last part of the ‘bellow’ has a growling sound. When bellowing, the alligator holds his head level with the water, which gives added force and pitch to is voice, and on a still day in the Swamp a large alligators bellowing is heard for miles.”
iNaturalist observation: https://www.inaturalist.org/observations/32689299
Okefenokee Photography Project by William Wise 