Another of the humpback whale’s showy surface behaviors is a powerful maneuver known as a peduncle throw. The peduncle on a whale is the muscular rear flank and attachment point where the tail fluke connects to the body. A peduncle throw, sometimes called a tail breach, is a maneuver where a humpback pivots its head downward and uses its large pectoral fins for leverage to execute a quick, powerful upward and sideways thrust of the fluke and peduncle: the whale throws its peduncle sideways, landing with a huge splash of water.
As with most humpback whale behaviors, peduncle throws likely have different meanings in different contexts. It is generally regarded as an aggressive or defensive action and is frequently seen employed between whales in a competitive rowdy group, as either an escort fighting off a primary challenger or as a female fending off unwanted advances of an unfavored escort. In other instances between a mother and a calf, peduncle throws seem to be used as a form of discipline for a wayward calf, and can also be used defensively to ward off a threat to the calf, but as mothers and calves can be seen performing throws together, it may also be for teaching self defense or simply for fun.