The occurrence of Pontoporia blainvillei (Gervais & d'Orbigny) (Cetacea, Pontoporiidae) in an estuarine area in southern Brazil

Abstract

The toninha, or franciscana, Pontoporia blainvillei (Gervais & D'Orbigny, 1844), is an endemic species of cetacean of the southwestern Atlantic Ocean. There is little information on the occurrence of this species in its natural environment due to the great difficulty in sighting it. Systematized and non-systematized observations of franciscanas were made from December 1996 through November 2001 at Babitonga Bay, on the northern coast of Santa Catarina State, southern Brazil. The observations were made from small motorboats. A total of 79 observations were made, totaling 561 individuals. Up to 59.5% of the groups consisted of over four individuals and the average group size was seven. Calves were present in 30.4% of the observations. The species was found throughout the year within the bay and preferential areas were identified. Calves were registered during all seasons. Data are presented on the behavior (feeding, traveling, aerial behavior and behavior relating to the boats) and on inter-specific interactions with terns, cormorants [Phalacrocorax brasilianus (Gmelin, 1789)] and brown boobies [Sula leucogaster (Boddaert, 1783)]. The species is sympatric with the estuarine dolphin Sotalia guianensis (P. J. Van Bénéden, 1864) in the bay, but there was no record of interaction between them. The area of the bay represents an important refuge for the franciscana species.