Group dynamics and activity patterns of two dolphin species, the Common Dolphin (Delphinus delphis) and Dusky Dolphin (Lagenorhynchus obscurus) in direct sympatry.

This article examines the co-occurrence, group dynamics, and activity budgets of two sympatric dolphin species—the Common Dolphin (Delphinus delphis) and Dusky Dolphin (Lagenorhynchus obscurus)—in the San Matías Gulf, Northern Patagonia, Argentina. Based on nautical surveys conducted from 2006 to 2018, the study found that Common Dolphins are present year-round in larger groups, while Dusky Dolphins mainly occur in spring and summer in smaller groups, with multispecies groups forming primarily during these seasons. Activity budgets differed between species, with Dusky Dolphins spending more time feeding, and multispecies groups exhibiting longer feeding bouts, suggesting cooperative foraging benefits. Seasonal and diel variations in group size and behavior indicate niche segregation beyond spatial and dietary dimensions, facilitating coexistence through temporal and behavioral partitioning in response to environmental conditions.