A new study adds Atlantic spotted dolphins to the list of animals that show nurturant behavior toward dead offspring.

Filipe Alves of the University of Porto in Portugal and colleagues observed two instances off Madeira Island. In the first event, recorded by a tourist boat operator, four adult dolphins were supporting a dead calf at the water's surface with their heads and backs. After about 30 minutes, the entire group of dolphins moved on, leaving the dead calf behind. In the second event, observed by a research vessel, one adult, presumably the mother, was supporting a dead calf at the surface.

In both cases, the highly fresh condition of the calves suggested they had died recently. The research team reported collecting two other dead calves, seen floating with no other dolphins nearby. Both carcasses were fresh, suggesting they had died recently and were abandoned after a short period of time.

NOAA Southeast Fisheries Science Center, via Wikimedia Commons.

Behavior like supporting dead calves at the surface has been documented in several other dolphin species, including bottlenose dolphins and long-beaked common dolphins. "The difference is that our study suggests that the adult Atlantic spotted dolphins tend to abandon the carcasses after a short-term period (minutes to a few hours)," says Alves. "There are records of other dolphin species carrying carcasses for several days, even after they begin to decompose."

Attention and supportive behavior toward dead offspring has also been observed in toothed whales, sea otters, harbor seals, monkeys, apes, and elephants. What these species have in common is they are all mammals.

While it is difficult to interpret what exactly this behavior means, Alves believes we can say that dolphins grieve for their dead.

"Species that live in a matrilineal system, such as killer whales and elephants; species that live in pods of related individuals, such as pilot whales whose pods can comprise up to four generations of animals—when they spend a lifetime together, sometimes 60 years or more, yes, I believe they can grieve."

Reference:

Alves, F., Nicolau, C., Dinis, A., Ribeiro, C., and Freitas, L. (2014). Supportive behavior of free-ranging Atlantic spotted dolphins (Stenella frontalis) toward dead neonates, with data on perinatal mortality. Acta Ethologica. doi: 10.1007/s10211-014-0210-8.