Sperm whales head-butting was captured on camera for the first time. The fearsome head-butting that even inspired novels about 19th-century whaling ships sinking has been confirmed as a natural whale behavior, not sailors tall tales. Why whales head-butt each other remains unknown. Scientists plan to determine through further research whether it is a kind of play that forges social bonds or an intense hierarchy contest among males.
A team led by Alec Burslem of the University of St Andrews said in Marine Mammal Science on the 23rd that "between 2000 and 2002, we filmed sperm whales bumping heads with drones in the Azores and the Balearic Islands in the North Atlantic." This is the first scientific confirmation of head-butting in sperm whales.
◇The first sighting of ship-sinking heading
The sperm whale is a large whale that reaches 15 meters in length and weighs 50 tons. It is the largest of the toothed whales, which bite prey with teeth like orcas and dolphins. It also has by far the largest brain volume among whales. Since the 19th century, sperm whales have been known as terrifying animals that ram and sink ships. The protagonist of Herman Melville's 1851 novel "Moby-Dick" is a sperm whale.
The St Andrews team worked with the University of the Azores in Portugal and Association Tursiops, a whale research institute in Spain, to track sperm whales in the North Atlantic with drones. After three years of research, they captured three instances of sperm whales ramming each other. Two cases are presumed collisions between individuals thought to be juvenile males, and in one case a male rammed a female's torso with his head.
The force was greatest in the case of the male attacking the female, at about 200 kilonewtons. It was enough to visibly displace the female's body centerline. A newton is the force needed to accelerate a 1-kilogram mass at 1 meter per second squared. When a 1.5-ton car hits a wall at 100 kilometers per hour, the force—considering 0.2 seconds for the airbag to deploy and the body to crumple—comes to about 200 kilonewtons. That gives a sense of how powerful a sperm whale's heading can be.
In fact, the American whaling ship Essex, a 27-meter sailing vessel, sank in the South Pacific on Nov. 20, 1820, after an attack by a sperm whale. It was the incident that inspired Moby-Dick. According to a record left by the first mate, the whale charged from 500 meters away at twice its usual speed and rammed the ship. There have been several other cases of sperm whales sinking ships besides the Essex.
The researchers did not clearly determine why sperm whales head-butt. There are two hypotheses. One is male-male competition. In fact, most of the whales that head-butted this time were males. However, heading in whales is unlikely to have been advantageous in evolution. That is because whales emit ultrasound from the head to navigate and communicate with companions.
Another possibility is that whales do head-butting as play. It may be a process of practicing and preparing for competition, courtship, or sexual behavior that young whales will face as they mature. This is common behavior in other mammals as well. In fact, the observation of juvenile males exposing their genitals while head-butting suggests a possible connection to a sexual context. The team also explained that the head-butting itself appears more like extending the head to make contact rather than full-power, head-on collisions.
The researchers said more observation is needed to understand why sperm whales head-butt. Fortunately, unlike in the past, the advent of new technology such as drones is expected to yield many more observations.
◇A mysterious animal that sleeps upright
The sperm whale is an endangered species whose numbers plummeted after rampant overhunting for ambergris and whale oil. Ambergris is a mass of intestinal secretions expelled by sperm whales and was used as a fixative in top-tier perfumes. Even in the 18th century, more than 1.1 million sperm whales lived worldwide, but with the rise of commercial whaling, their population is estimated to have fallen to 29% by 1880.
To save the sperm whale, we must first understand what it is. Yet despite its massive size, much remains unknown. One prime example is sleeping upright with the head pointed toward the surface in the water. Whales and dolphins are known to keep one hemisphere of the brain awake even during sleep. The idea is that they cannot fall into deep sleep for fear that predators may approach. They keep one eye open, swim, and breathe. But sperm whales showed the entire brain entering a fully resting state, with no sign of movement.
A team led by Patrick Miller of the University of St Andrews first reported in Current Biology in 2008 that sperm whales sleep upright. Observations showed that sperm whales descend vertically from the surface, then reverse direction by 180 degrees and drift upward with their heads pointed toward the surface, relaxing their bodies and falling asleep.
The time spent sleeping upright was very short. Measurements showed it accounted for only 7.1% of total time. It lasted as little as 6 minutes to as long as 24 minutes. That is far shorter than the 32% for belugas or 42% for gray whales. The researchers estimated that a fully deep sleep across the entire brain could allow recovery of vigor even in a short period.
References
Marine Mammal Science (2026), DOI: https://doi.org/10.1111/mms.70153
Current Biology (2008), DOI: https://doi.org/10.1016/j.cub.2007.11.003