Behavior and seasonal variation in the relative abundance of Commerson's dolphins Cephalorhynchus commersonii in northern Patagonia, Argentina

COSCARELLA, MARIANO ALBERTO; PEDRAZA, SUSANA NOEMÍ; CRESPO, ENRIQUE ALBERTO

Journal of Ethology

Sringer-Japan

Lugar: Tokio; Año: 2010 vol. 28 p. 463 - 470

0289-0771

Commerson´s dolphins (Cephalorhynchus commersonii) along the Patagonian coast of South America suffer incidental mortality in fisheries and are the target of a dolphin-watching industry. We describe the daily activity patterns and assess the variation in the relative abundance of the species near the northern boundary of its range. Information was gathered with a spotting scope from a clifftop vantage point applying the method of scan sampling. Behaviors were categorized as individual feeding, cooperative feeding, directional swimming, socializing and resting. These behaviors are similar to those observed in other species of small cetacean but differences were found regarding the patterns of directional swimming and feeding techniques. Hunting tactics favored the association of terns with dolphin groups. No clear dial behavioral pattern was observed, but seasonal changes in the frequency of behaviors were recorded. Group and school sizes were larger during periods with colder sea surface temperature (SST). Seasonal abundance was correlated with SST, suggesting that at higher SST the species forsakes the area, probably in favor coastal areas to the south with lower SST.