Abstract

The Chilean dolphin, Cephalorhynchus eutropia, is an endemic species distributed along the central-southern coast of Chile. Biological and ecological knowledge about this species is insufficient; it is catalogued as Data Deficient "DD" by the World Conservation Union. This study provides information on the species' occurrence and distribution along the central Chilean coast from January 2000 to March 2001. Monthly land-based surveys were performed within the study area, which was divided by the Maule River outlet, with the northern area more influenced by an estuarine system than the southern one. Chilean dolphins were sighted in 83% of surveys. The relative abundance was significantly higher in the northern than the southern area (13.6 dolphins/h versus 3.5 dolphins/h). Three behaviour categories were recorded (feeding, socialising, and travelling) in both areas, however, these were more frequently observed in the northern area. We suggest that the area located north of Maule River is the preferred zone for Chilean dolphins within the study area. This study shows a year-round occurrence of Chilean dolphin in the study area which is possibly a critical habitat for this species. Further research focused on population structure assessment and residence patterns of the species in the study area is required. © The Royal Society of New Zealand 2007.