Pectoral Slapping and Surface Displays from Nine Humpbacks

Calm, glassy conditions greeted us across Monterey Bay this morning aboard Sanctuary. Out on the water, we observed pronounced surface activity from several of the nine humpback whales logged during the trip, including repeated pectoral fin slaps, tail slaps, and slow barrel rolls at the surface.

Pectoral slapping—striking their elongated flippers against the water—and tail lobbing produce acoustic signals that carry well through the water column. In calm conditions like today's, these percussive strikes resonate audibly above the surface as well, serving communicative and social functions among dispersed individuals.

In addition to the nine humpbacks, we observed approximately forty California sea lions resting and traveling through the area. The low swell and glassy surface provided clean visibility of the whales' movements, including the distinct white undersides of their flippers turning just below the water line during each roll.

Observing such energetic surface displays in flat conditions offers a detailed look at the physical coordination and behavioral repertoire of these animals on the bay.