Diurnal and seasonal behavior patterns of Tursiops-truncatus and Stenella-attenuata (Mammalia : Delphinidae) in Golfo Dulce, Costa Rica

From July 1996 to June 1997, 123 sightings of bottlenose dolphins and 17 si ghtings of spotted dolphins were made in Golfo Dulce, south Pacific of Cost a Pica. Behavioral patterns of both bottlenose and spotted dolphins were an alyzed, classifying behavior in five categories such as travelling, feeding , passive socializing, active socializing and milling. Instantaneous data r ecording was used, and only sightings equal or longer than 15 minutes were considered. Correspondence Analysis revealed differences in diurnal pattern s between the two species while seasonal patterns showed important similari ties. Diurnal differences were explained in terms of external aspects (i.e. prey) instead of internal requirements due to time proportions for each ac tivity were similar. Coincidence of time proportion spent on feeding activi ties during dry season (January-April) as well as coincidence of time propo rtion invested on active social activities during late wet season (Septembe r-December) in the two species were explained on a survival basis.