A group of sperm whales did something scientists had never seen this clearly before. Off Dominica in July 2023, two family groups came together and took turns helping a calf be born, then kept the newborn at the surface so it could breathe.
The event is described in a new study published in Science Advances. Researchers say it is the first detailed record of this kind of coordinated birth support in sperm whales.
Over several hours on July 8, 2023, scientists recorded two sperm whale family groups in the Caribbean Sea off Dominica. The groups were unrelated matrilines that usually forage separately.
“Our results suggest that kin and non-kin engaged in sustained, cooperative postnatal care, taking turns to support the newborn and maintain group cohesion, in contrast to historical kin-segregated foraging patterns,” wrote a cross-disciplinary team led by computer scientist Alaa Maalouf of MIT’s Project CETI.
“These findings provide rare quantitative evidence of direct allocare [caring for non-biologically related offspring] in cetaceans and can lend support to the hypothesis that transient, structured cooperation during birth is a key mechanism sustaining complex sociality in sperm whales.”
Sperm whales are highly social animals and live in groups. Their smallest clan units can include up to 10 individuals and are matrilineal, led by a mother and made up of her daughters. Adult males usually live separately and only visit female groups for reproduction.
Scientists do not know much about how that social structure works during births. Before this event, only four sperm whale births had been reported in the past 60 years, and all were either anecdotal or observed in whaling contexts. Those reports suggested some level of group support, but it had not been documented in detail.
Maalouf and his colleagues were already in the field off Dominica in July 2023 as part of Project CETI, which is trying to decipher sperm whale communication using recordings and machine learning.
At 9:50 am local time, researchers came across a group of 11 sperm whales gathered at the surface. The behaviour was unusual enough that the team stopped and deployed observational tools including hydrophones for audio and drones for overhead video.
At 11:12 am, a pregnant whale known as Rounder began delivering her calf. The birth took 34 minutes. Other adult females positioned themselves around her in a tight, synchronized formation. At 11:46 am, scientists saw plumes of blood and the newborn calf.
What followed lasted about an hour. According to the study, newborn sperm whales are likely unable to stay afloat on their own, so members of the extended group took turns lifting and pushing the calf to the surface to breathe.
“The group rapidly transitioned to cohesive and highly active behavior; individuals took turns lifting the newborn, physically supporting and pushing it to the surface, consistent with supporting a negatively buoyant neonate. This phase continued for about an hour, during which time the entire unit remained tightly grouped,” the researchers wrote.
The study also recorded other cetaceans nearby during the birth.
“In addition, there were close passes by Fraser’s dolphins (Lagenodelphis hosei) and brief interactions with pilot whales (Globicephala macrorhynchus), which encompassed the sperm whale cluster and occasionally dove beneath them.”
To work out exactly what happened, the team used machine learning and computer vision to identify individual whales, track their movements and examine how they interacted during and after the birth.
That analysis found all 11 whales in the group took at least one turn supporting the calf in the hour after birth. About 96 percent of that support time came from four whales: Rounder, the mother; Aurora, her half-sister; Ariel, a juvenile unrelated to Rounder; and Atwood, an older relative of Rounder.
Researchers also recorded an active acoustic environment throughout the birth, but the new study did not analyse what the whales were vocalising. It focused on their actions.
Still, the team says the observations add to the understanding of sperm whale social behaviour.
“Our results provide quantitative evidence for the paradigm that calf survival, particularly around births, drives selection for the social bonds underpinning the complex social organization that has evolved in sperm whales,” the researchers wrote.
“These findings place the complexity of sperm whale birth behavior and coordination in comparative context with terrestrial mammals, including primates and humans, raising questions about the cognitive architectures and communication systems that support and mediate these behaviors.”
📸credit: Project CETI
