Costero - Behavior

Behavior

This species forms small groups of about 10-15 individuals, occasionally up to 30, and swim in tight-knit groups, suggesting a highly developed social structure. They are quite active and may jump clear of the water (a behavior known as breaching), somersault, spy-hop or tail-splash. They are unlikely, however, to approach boats. They feed on a wide variety of fish. Studies of growth layers suggest the species can live up to 30 years.

In December 2006, researchers from the Southern University of Chile and the Rural Federal University of Rio de Janeiro witnessed attempted infanticide by a group of costero dolphins in Sepetiba Bay, Brazil. A group of six adults separated a mother from her calf, four then keeping her at bay by ramming her and hitting her with their flukes. The other two adults rammed the calf, held it under water, then threw it into the air and held it under water again. The mother was seen again in a few days, but not her calf. Since females become sexually receptive within a few days of losing a calf, and the group of attacking males was sexually interested in the female, it is possible that the infanticide occurred for this reason. Infanticide has been reported twice before in bottlenose dolphins, but is thought to be generally uncommon among cetaceans.