Being born directly into the aquatic environment presents unqiue challenges for the breathing muscles of neonatal dolphins and manatees. Not only must these muscles function from the moment of birth to allow gas exchange, but their activities must also be coordinated such that breathing occurs at the surface. However, the breathing muscles of dolphin and manatee neonates are able to deal with these demands. Thus, I hypothesize that these muscles are well-developed at birth, as demonstrated by the histohcemical and biochemical activities of their component muscle fibers.