Birth of a sperm whale: eleven females from two unrelated families take turns keeping the newborn at the surface

On 8 July 2023, off Dominica, a drone filmed the birth of a sperm whale. Around the mother, eleven animals belonging to two maternal lines with no kinship between them, which do not normally associate, took turns for an hour supporting and lifting the newborn towards the surface. Published on 26 March 2026 in Science, the analysis constitutes the first quantified demonstration of birth assistance outside humans and a few primates.

What was observed

Births of wild cetaceans have been observed in fewer than 10% of species. In the sperm whale, an animal of the open sea and of great depth, they were until now practically unknown.

That day, the team spotted eleven members of a known social unit, gathered unusually close to the surface. The birth lasted 34 minutes. In the hour that followed, the females surrounded the mother and took turns physically carrying the newborn towards the open air, a gesture that in all likelihood helps it to breathe. The group remained tightly organised throughout this phase, then dispersed several hours later into the usual small foraging groups. Fraser’s dolphins passed nearby, and pilot whales interacted briefly.

Long-term monitoring gives the scene an unusual depth. The mother, known to researchers as Rounder since 2005, was accompanied by her own mother, Lady Oracle, and by her daughter, Accra: three generations of females present at the birth.

The result: kinship stops counting

This is the heart of the paper, and it is worth understanding why it is surprising.

Sperm whale societies rest on stable matrilines: grandmothers, mothers, sisters and daughters that live together. When two unrelated lineages share a single unit, they usually remain distinct in their associations and in their foraging activity. Mutual aid between relatives is readily explained in evolutionary biology: helping a close relative amounts to favouring genes one shares.

Here, however, the kinship barrier dissolved. A relative of the mother appears to have led the assistance during labour, but after the delivery every individual in the unit, related or not, turned towards the newborn and took part in the carrying, each in turn.

The interpretation advanced by the authors is that of reciprocity: helping an unrelated companion today encourages being helped tomorrow. These brief and intensely coordinated episodes would consolidate the bonds on which their whole society rests. Our pages on the social cohesion of cetaceans and on sperm whale culture set this social architecture in context.

How mutual aid is quantified

Describing a scene is one thing, measuring it another. The set-up combines four elements.

Raw data	more than six hours of aerial drone video and underwater audio
Extraction	computer vision, with a software tool developed for this analysis
Analysis	multi-scale networks, to describe who interacts with whom and when
Context	twenty years of individual monitoring and genealogy of this unit

Diana Reiss, of Hunter College, stresses a point that the technical papers rarely mention: an observation of this kind presupposes that the animals tolerate the close presence of observers, something gained only after years of familiarity. The scientific result therefore rests as much on the technology as on two decades of fieldwork led by Shane Gero and the Dominica Sperm Whale Project.

The second paper: the voice changes during the event

A companion paper appeared the same day in Scientific Reports. It gives the minute-by-minute sequence and turns to the soundtrack.

Sperm whales communicate through codas, short rhythmic sequences of clicks. The analysis reveals clear shifts of vocal style at the key moments of the birth, as well as structures that the authors describe as comparable to vowels. This vocabulary calls for caution: it designates an acoustic organisation of the signal, not an articulate language. Our page on the acoustic profile of cetaceans distinguishes these levels, and our sound library makes it possible to hear codas.

A behaviour perhaps 36 million years old

The authors go further by placing this behaviour in the evolutionary tree. A phylogenetic analysis suggests that the collective carrying of newborns could predate the last common ancestor of the toothed whales, that is, more than 36 million years.

In other words, it would not be a cultural invention peculiar to one unit off Dominica, but an ancient trait of the group. The approach consists in comparing the distribution of the behaviour among related species and inferring its antiquity from that: it is a reconstruction, sound in principle, but one that remains an inference. Our page on the evolution of cetaceans gives the temporal framework.

The limit, which is also the strength

It has to be said plainly: this is a single event. One birth, one unit, one day. However finely documented it may be, a single observation does not establish a rule for a species, and nothing guarantees that all sperm whale births unfold in this way.

But that is precisely the nature of the subject. In an animal that gives birth on the open sea, once every four to six years, waiting for a statistical sample would amount to never publishing anything. The value of this work lies in the density of the documentation: where only occasional descriptions were available, there are now measurements, temporal sequences and a named network of interactions.

Two years earlier, a humpback whale birth filmed by drone in Australia had already shown what this tool brings to the study of a moment that had been invisible until then. Our pages on life cycles and lactation detail what follows the birth.

References: Maalouf A., DelPreto J., Lucas M. et al., “Cooperation by non-kin during birth underpins sperm whale social complexity”, Science, 391, pp. 1355-1360, 26 March 2026; Aluma Y., Baron Z., Barrett R. et al., “Description of a collaborative sperm whale birth and shifts in coda vocal styles during key events”, Scientific Reports, 26 March 2026. Releases from the AAAS and from Project CETI. Fieldwork carried out by the Dominica Sperm Whale Project.