Built-in shock absorbers suggest that sperm whales could use their heads as battering rams to fight other whales or perhaps sink a ship—just like the whale in Herman Melville’s Moby Dick.
“The forehead of the sperm whale is one of the strangest structures in the animal kingdom,” says Olga Panagiotopoulous, lecturer in the school of biomedical sciences at the University of Queensland.
“The forehead of the sperm whale is one of the strangest structures in the animal kingdom.”
“Internally, the whale’s forehead is composed of two large oil-filled sacs stacked on top of each other, known as the spermaceti organ and the junk sacs. The oil in the upper spermaceti organ was the main target of the whaling industry in the early 19th century.”
Male sperm whale heads are much larger than those of the females. “Such difference between the sexes are commonly found in species in which males fight to compete for females,” Panagiotopoulou says.
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The battering ram function of sperm whale heads was first proposed by a 19th-century whaler.
“After a large male rammed and sank his ship in the Pacific in 1820, whaler Owen Chase described the whale’s head as admirably designed for this mode of attack. The theory was instrumental in inspiring Herman Melville’s novel Moby Dick, but until our research, its mechanical feasibility had never been addressed.”
The ramming theory has, until now, been met with some skepticism from scientists, Panagiotopoulou says, largely because the front part of the sperm whale head houses sensitive anatomical structures that are essential for sonar communication between whales, that could be harmed by ramming.
The sperm whale head has an important role in transmitting sonar clicks and potentially assisting in communication and buoyancy, says David Carrier, a professor at the University of Utah.
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But there is no explanation of how the sperm whale head could function as a weapon capable of sinking ships that are four to five times the mass of the whale, so researchers used structural engineering principles and computer models to test how the sperm whale’s head might withstand ramming impacts.
The findings, published in the journal PeerJ, show that while whale ramming can potentially could cause fatal fractures, “connective tissue partitions within the junk of the sperm whale forehead may function as a shock absorber,” Panagiotopoulou says.
“This mechanism is important to reduce impact stress and protect the skull from failure. The mechanical advantage of the junk’s structure may be the result of selection and acquired traits related to male-to-male aggressive behavior.
“Male sperm whales may not fight frequently, but we know that aggressive ramming behavior is a common characteristic in bottle nosed whales, killer whales, narwhals, pilot whales, and the group of mammals from which whales are derived—the even-toed ungulates, such as goats.
“A closer look into the anatomy of the heads of other species that ram (such as monkeys and hippopotamuses) may reveal a variety of protective mechanisms. Our study has limitations but we hope it might stimulate future research to unravel the mechanical function of the head during head-butting events in other species, where aggressive behavior has been observed but remains unmodeled.”
Source: University of Queensland