As early as the 19th century, whalers repeatedly reported that sperm whales attacked their ships with headbutts and sometimes even sank them. The novel “Moby Dick” also takes up this motif. For a long time, however, such stories were considered unbelievable. But now researchers have documented on video how young male sperm whales use their heads as battering rams against members of their own species of both sexes – sometimes with considerable force. It is still unclear what function the behavior fulfills.
In 1820, the 27 meter long whaling ship “Essex” sank off the Galapagos Islands. According to reports from the first mate, the ship was head-rammed several times by a huge sperm whale and thus destroyed. This event, as well as other anecdotes of similar events, inspired the American author Herman Melville to write his book “Moby Dick,” published in 1851, in which the white sperm whale of the same name sinks a whaling ship.
But do sperm whales really use their heads as a weapon? Scientists had doubts about this for a long time, especially since the head of sperm whales contains sensitive organs with which the animals produce sounds for communication and echolocation. “Although mathematical modeling has shown that the anatomical structures of the sperm whale’s head can probably withstand the large forces of a headbutt, this is not proof that this behavior actually occurs in nature,” explains a team led by Alec Burslem from the University of St. Andrews in Scotland.
Headbutts filmed by drone
But now Burslem and his colleagues have actually observed and filmed sperm whales headbutting each other. Between 2020 and 2022, the researchers observed sperm whales off the Azores and Balearic Islands using drones. They happened to record three cases in which the animals used their heads as battering rams. “It was really exciting to observe this behavior that had been suspected for so long but not yet systematically described,” says Burslem.
While anecdotal reports attribute the behavior to adult males, the researchers’ videos always showed male juveniles headbutting others. In two cases, two young males repeatedly rammed each other’s heads, sometimes head to head, sometimes with their head to the side of the other’s body. At one point, a third, larger whale happened to be nearby and the researchers had previously equipped it with a microphone. This meant that Burslem and his colleagues were also able to eavesdrop on the wrestling young bulls. Accordingly, the two participants communicated actively with the clicking sounds typical of whales.
Another case involved two young males with erect penises and a smaller female. The two males initially swam around each other before one of the two attacked the female with a strong push in the side. “This impact appeared to be targeted and occurred with considerable force, as the female’s body was clearly pushed to the side,” report the researchers. The female then swam away without being chased by any of the males.
Function remains a mystery
To understand the social function of these shocks, more extensive observations are needed, according to Burslem and his team. It is possible, they write, that the observed activities between young bulls are a kind of combative game that prepares the animals for later battles for rank. Aggressive attacks against females, who are actually higher-ranking whales in the social system, could lead to young males being expelled from the family group when they reach puberty.
Since all three observations now published were collected by chance within just two years, the researchers assume that the behavior occurs more frequently than previously assumed. As drone-based wildlife observation capabilities continue to expand, they expect to soon be able to capture more footage of sperm whale head-butting and other behaviors. “It’s exciting to think about what previously unknown behaviors we might soon discover and how further observations of head impacts might help us shed light on the functions this behavior serves,” says Burslem.
Source: Alec Burslem (University of St. Andrews, Scotland) et al., Marine Mammal Science, doi: 10.1111/mms.70153