Commonly referred to as “pec slapping,” this is when a whale lying on it’s side repeatedly raises a long pectoral fin into the air and slams it back to the surface with a loud splash. It’s another way the whales communicate with each other. For example females may slap their fins provocatively to attract males or pairs of whales may pec slap as part of their mutual flirtation.
Humpback whales have a powerful ball and socket joint where the fins attach to their bodies. It’s similar to a human shoulder and gives them a remarkable range of motion. Sometimes the whale will simply drop their fin lazily, or slam it down with great force. They may also lie on their back and slap both fins, alternately.
Reaching up to 15′ in length a good pec slap makes for quite a show and you’ll this behavior almost every day on the Silver Bank.