Sperm whale foreheads may be specialized for ramming
© Peabody Essex Museum, Salem, Massachusetts/Bridgeman Images

Sperm whale foreheads may be specialized for ramming

Ever since a sperm whale (Physeter macrocephalus) head-butted and sunk a whaler’s ship in 1821, whalers and scientists have theorized that the mammals’ uniquely boxy foreheads might be adapted for use as battering rams—possibly for male-on-male battles over access to females. But not everyone agrees, especially because the structures that would be front and center in an impact are important for producing the whale’s clicking communication. In a new study, researchers tested the idea by running virtual crash tests: Using a model of a sperm whale skull constructed using already published data, they simulated ramming impacts, and recorded where in the skull these impacts produce the most mechanical stress. To examine the role of internal structures, the researchers also removed the vertical tissues that divide up the large, oil-filled organ called the “junk” in some models. The simulations showed that these junk compartments help spread the force of impact over the skull, and removing the compartments increased overall stress on the skull by 45%. Plus, the compartment tissues are thickest near the front of the skull—the same area where impact forces are the most intense, the authors report today in the journal PeerJ. Male ramming behavior has only been observed once in sperm whales. But based on their ram-ready skulls, the authors say, these contests may be occurring below the surface.