Lobtailing is when a whale lifts its fluke (tail fin) out of the water and brings it down forcefully to slap the surface of the water with a big splash and loud report. Lobtailing is most likely a form of non-verbal communication, like breaching or pectoral fin slapping, and can be used to call attention to an individual, to impress a potential mate or intimidate a foe.
The slap can be heard from great distances above the ocean’s surface and below. On the Silver Bank it is not unusual for one lobtailing whale to be “answered” by another in the area or to see a pair of whales lobtailing together.
Humpback whales will frequently lobtail repeatedly and for several minutes at a time, and can lobtail both dorsally and ventrally (right side up and upside down), sometimes stopping just long enough to take a breath before rolling over to continue on the other side.