Diurnal behavior of dusky dolphins, Lagenorhynchus obscurus, in Golfo Nuevo, Argentina

MARIANA DEGRATI,; SILVANA DANS; SUSANA PEDRAZA; ENRIQUE CRESPO; GRISELDA GARAFFO

JOURNAL OF MAMMALOGY

Allen Press

Año: 2008 vol. 89 p. 1241 - 1247

0022-2372

Standardized measures of behavior can be powerful tools for predicting effects of human activities on natural populations of mammals. This study quantifies the diurnal activity budget of dusky dolphins (Lagenorhynchus obscurus) in Golfo Nuevo, Argentina, by examining variation in activity as a function of season and age composition of social groups. Observations were made from a research vessel during summer and autumn from 2001 to 2005. Focal group follow methodology was used. The predominant activity in each social group was recorded using instantaneous sampling, with a 2 minute inter-scan interval. The main daytime activity of dusky dolphins was traveling, followed by milling and feeding. Mother and calf pairs spent more time milling and resting, while larger groups of adults and juveniles as well as mixed age class groups spent more time traveling and feeding. Although a seasonal pattern of variation in group size and composition was found, little seasonal variation was found in activity budget, which was almost constant during daylight hours. The activity budget generated by this study provides a baseline for detection of behavioral differences associated with tourism and other human activity in the region.