Behavioral observations of the marine tucuxi dolphin (Sotalia fluviatilis) in Sao Paulo estuarine waters, Southeastern Brazil

The marine tucuxi (Sotalia fluviatilis) is one of the lesser-known delphinids. Many aspects on this species' natural history and behavior remain unknown. Herein, we present some behavioral observations of tucuxis found in Sao Paulo State estuarine waters, Southeastern Brazil. Three observations took place at the Cananeia Estuary (25 degree 00'S, 48 degree 55'W), and the other one at the Santos estuarine and nearby coastal waters (23 degree 58'S, 46 degree 21'W). These observations were reported from 1995 until 1999 and lasted from 2 h to 24 months. Behavioral aspects were reported through the ad. libitum (sensu Altmann, 1974) sampling method. At the Cananeia estuary, the marine tucuxi epimeletic or care-giving behavior was noticed in 1995. A dead calf was carried for about 2 h by an adult dolphin, probably its mother. This notification adds tucuxi to the list of cetacean species in which carrying dead calves in the wild has been described. In the same estuarine waters and in 1996, we reported an individual tucuxi that was hand-fed by local fishermen. Tourists noticed other observations and some photographs showed that more than one dolphin had been hand-fed in local estuarine waters. From 1996 to 1998, tucuxis were observed spontaneously swimming with 2 domestic dogs (Canis familiaris) at a local beach placed at the same estuarine connection with the sea. These interactions occurred because local tucuxis approach sand banks close to that beach to prey on fishes. A case of a lone and sociable tucuxi was reported at the Santos estuary from 1998 to 1999. A 160 cm long male interacted with boats and bathers for about 10 months, then it disappeared. This is the first known case of a lone and sociable marine tucuxi.