First recording of a sperm whale ‘delivering a baby’ to its fellow species

A team of scientists from CETI, an international project aimed at understanding how whales communicate, released footage of sperm whales (Physeter macrocephalus), belonging to the suborder Whales, gave birth off the coast of Dominica island, Caribbean Sea, July 8, 2023. New research published in two journals Scientific Reports and Science this week, showing an extremely rare sight in the history of science.

Rounder, a 19-year-old female sperm whale, was surrounded by the remaining 10 members of the herd to help her as she prepared to give birth. For nearly five and a half hours, scientists observed and recorded their behavior from the boat, filming with a drone and recording sounds under the waves.

Of the 93 species of whales, to date only 9 have been observed reproducing in the wild. Rounder’s case is even more rare when individuals unrelated to it also come to help. “This is the first evidence of assisted birth in a non-primate species,” CETI Project team member Shane Gero told New Scientist.

The birth process lasts about 34 minutes. During this time, other adult females dive under the Rounder’s dorsal fin, often tilting their heads up and looking toward the spot where the young emerged.

Soon, they gather and take turns keeping the juvenile afloat on the water’s surface to breathe and have time for the tail to fully spread. During the first few hours, a newborn sperm whale cannot float or swim on its own, so this support is especially important to keep it from sinking. They are also born with their tails first instead of their heads like other mammals to avoid drowning.

The team of scientists also recorded many of the sounds of sperm whales, including significant changes in “vocal style” at key moments, for example when Rounder began labor and when a group of short-finned pilot whales approached, triggering a defense response. The research team said the changes in vocalizations show that the sperm whales are coordinating to support the birthing process or protect the young.

After filming Rounder’s calf being born in 2023, scientists did not see the sperm whales again for more than a year. On July 25, 2025, they encountered this juvenile with Accra and Aurora – two other young members of the herd. The CETI Project team said that surviving its first year is a good sign that the sperm whale will reach adulthood.

Sperm whales have the longest gestation period in the animal world, lasting up to 16 months. At birth, the calf is up to 4 m long. They depend on mother’s milk for at least two years. During development, they are central to the social structure of the group, assisted by other members in looking after them while the mother sperm whale goes out to forage.