Male Franciscana Dolphins Babysit Calves Near Ubatuba, Brazil

Male franciscana dolphins babysit calves, and nobody expected to write that sentence. Marine biologist Marcos Cesar de Oliveira Santos of the University of Sao Paulo and his team recorded males caring for calves almost 300 times over a year and a half near Ubatuba, Brazil, and they published the findings in the journal Marine Mammal Science.

The pattern showed up in threes. Drones over the pods kept catching a mother, her calf and a smaller adult the team identified as male traveling together while the mother searched for food. When the mother dove, the calf and the male surfaced without her, and the male stayed close to the calf until she came back up for air.

He didn't just wait nearby. The male often helped guide the baby back to its mother once she resurfaced, Santos reported. That's active care, not coincidence of position, and it's why the team calls the behavior babysitting rather than escorting. The researchers describe it as the first documentation of male babysitting in dolphins.

Franciscanas are hard animals to learn this from. They're small, about five feet long, they live in murky coastal waters off Argentina, Uruguay and Brazil, and most of what science knew about them came from animals found dead in fishing nets. A living pod that tolerates a drone overhead is a rare window into how the species actually raises its young.

The open question is kinship. Santos wants DNA samples to learn whether the babysitting males are related to the calves they tend, because a father minding his own calf and an unrelated male minding someone else's point to different explanations. Until that work is done, the motive stays unproven, and the team says so.

The stakes aren't academic. Franciscana dolphins are classified as vulnerable, and their numbers are falling, largely because they get scooped up in fishing nets. A species that loses adults to bycatch can't spare caregivers, and a calf-minding system that depends on extra males is one more thing a shrinking population has to keep intact.

Other researchers urge the same caution the team applies to itself. Hal Whitehead of Dalhousie University, who wasn't involved in the study, has observed male pilot whales tending calves that may not be their own, so the franciscana pattern may belong to a wider, poorly watched set of behaviors in whales and dolphins. The difference here is the record: almost 300 drone-documented cases in one species, in one place, over 18 months, is harder to dismiss as an anecdote.