Ecology
Adult Amazonian dolphins are capable of killing newborn babies, new research has shown. For the first time, infanticide was reported among members of the dolphin species.
Although infanticide is common among many mammal species, it is quite rare among cetaceans, a group of marine animals that includes whales and dolphins.
So far, this behavior has been seen only twice among bottlenose dolphins, but new episodes may suggest that this phenomenon is more widespread than previously thought.
The Sotalia guianensis species of the long-billed dolphin genus can live both in fresh water in the Amazon basin and in salt water off the coast of Brazil and Nicaragua. Adult male Amazon dolphins are known to be aggressive towards each other during mating season, but they have never been seen to be aggressive towards young dolphins members of their own species.
Scientists from Chile's Southern University in Valdivia and the Federal Agrarian University of Rio de Janeiro, Brazil, studied dolphins in Sepetiba Bay in Brazil. On a December morning, when the sea was calm, they spotted a group of 6 Amazon dolphins approaching a mother with her newborn baby.
Two adult dolphins removed the baby from its mother. The mother took diversion maneuvers to get the intruders away from the cub, but the other 4 dolphins surrounded her, hit her with fins and ran into her. Any attempt by the mother to save the baby was thwarted by a pack that did not allow her passage.
Two adult dolphins began to take the cub to the depth, then threw it on the surface of the water and pushed it back to the bottom. After that, the cub lost its orientation and had difficulty moving. Although scientists saw the mother again a few days later, they did not see a baby near her.
“We think the cub suffered injuries from which it was unable to recover,” the researchers said.
It is difficult to say whether these were deliberate attempts to kill the baby or whether it was a strange playful behavior, but the fact that the cub then disappeared is disturbing. Scientists believe that dolphins also practice infanticide like some other animals.
In some animal species, males may kill cubs whose fathers they are not to encourage the female to become sexually receptive again. “Female dolphins can reconceive a few days after they lose their baby,” the researchers say. “This may be why the baby is killed so that the female becomes sexy again,” the researchers say. active.”