Marine biologists have yet to determine exactly why whales breach.
While marine biologists have recently paid attention to endangered whale species, they haven’t done enough research to know exactly why whales breach. A rupture occurs when a whale, especially a humpback, launches itself fully out of the water, writhes in the air, and lands noisily on its side. Tourists on whale-watching tours might think the hopping mammals make a break just to create photogenic moments, but it probably has more to do with communication, comfort, defense, or predatory behavior.
It is possible for whales to make a breach to scrape barnacles.
One theory suggests that whales breach as an alternative method of communication instead of their underwater sonar noises. The slap can probably be heard by other whales at a very long distance. However, what the whales are saying to each other can only be guessed at. Are they warning friends about plentiful food sources? Seductive companions? Or just announcing your presence?
Another theory is based on the fact that, after a breach, a large amount of dead skin and barnacles are released with the impact of the landing. Scientists who have tried to track individual whales based on their DNA have noticed this convenient way of collecting genetic material. Whether whales intentionally breach to scrape the top layer of skin, water lice, or barnacles, in the same way humans scratch with their fingernails, is unknown, but it seems plausible.
Perhaps whales have recently developed their frequent breaches in response to so many barges, boats, ships and people in the water. As they have adequate eyesight, they are believed to jump out of the ocean to see and be seen by human-powered craft. This gives them time to prepare for a moving ship and also warns the ship not to get too close to the area where the whales are gathering. This prevents injuries to both parties.
Two lesser-known theories have to do with traveling fast and attacking fish. Aerodynamically, briefly letting water into the air can help a whale swim fast over long distances. The breach may have energy efficiency aspects. Second, whales may purposely land on prey that they would not otherwise be able to consume without being bitten. The strong impact is known to render the prey unconscious long enough for the whale to swallow it.