Sperm whales' heads are perfectly evolved for ramming ships, suggests a new modelling study.
Whales' foreheads contain two sacs filled with oil. In male sperm whales, these sacs are especially massive. But quite what their purpose is not clear. Some biologists think they play a role in sound production or controlling buoyancy, but another theory is that the sperm whale's massive oil-filled sac cushions the animal's head during fights.
While there are a handful of anecdotal accounts of such contests between males, evidence has been scarce.
Now Stephen Deban and his team at the University of Utah have modelled how the fluid-filled sacs would behave in a collision. They found the organ acts like a damper, cushioning the impact. It is a bit like a syringe, says Deban, you do not need much force to push the water out slowly, but you need to squeeze much harder to push it out faster.
That means an attacking whale could smash into an opponent's side - or a ship - and come out of the encounter unscathed. What's more, whale species in which the males engage in more intense competition for mates also tend to have larger oil-filled sacs.
Whalers in the 19th century were all too aware of the dangers. The sinking of the Ann Alexander in 1851 - the year Herman Melville's Moby Dick was published - is one example.
Two head-on charges from a harpooned whale were enough to send the crew to a watery grave. But the sperm whale's weapon was also its downfall. It was the oil that made the creatures so highly prized in Melville's time.
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