Old seafaring tales of ships being sunk by sperm whales have been given scientific support by research showing that the leviathans’ huge heads are built, at least in part, for ramming.
“The idea that sperm whales use their foreheads as battering rams was first introduced by whalers after the sinking of two whaling ships, the Essex in 1821 and the Ann Alexander in 1851,” said Olga Panagiotopoulou of the University of Queensland. “After the Essex was sunk, Owen Chase, the ship’s first mate, proposed that ‘the whale’s head is admirably designed for this mode of attack’.”
Until now, however, scientists who study whales have not taken the idea seriously.
But by analysing the mechanical properties of the sperm whale’s head, Panagiotopoulou’s team has shown that a huge, fluid-filled chamber called the junk sac can absorb energy from forceful impacts that would otherwise fracture the skull.
“It often pays to listen to people who make their living working with animals,” Panagiotopoulou said of the finding.
The scientists argue that because the males’ heads are much bigger than females’, they are designed for ramming rivals when competing for females. A report of males ramming each other in the Gulf of California in 1997 bolsters the theory.
But why do females also possess the distinctive, bulbous forehead if only the males wield them aggressively? Panagiotopoulou said that the forehead has multiple functions – it is also important in echolocation, communication and buoyancy control, for example.
“The structural components within the forehead of both sexes are potentially adapted to all of these functions,” she added.
But there might be other reasons, too. Because males and females share almost all of their genes, features that are useful for one sex are often also found in the other.
In mammals, for example, only females nurse young, said Panagiotopoulou, “but male mammals have both mammary glands and nipples”.