Seasonal Occurrence and Behavior of an Endangered Franciscana Dolphin ( <scp> <i>Pontoporia blainvillei pukusi</i> </scp> ) Population

ABSTRACT The franciscana dolphin ( Pontoporia blainvillei ) is a threatened cetacean whose northernmost population (Franciscana Management Area Ia)—part of the recently described subspecies P. b. pukusi— faces significant anthropogenic pressures, including impacts from a major mining dam collapse. However, fundamental data on its seasonal ecology remain scarce. This study aimed to investigate the seasonal variation in occurrence, group composition, and behavior of this isolated population. Over 5 years (2018–2023) we conducted 1440 systematic drone surveys across three coastal sites in Espírito Santo, southeastern Brazil. Our results revealed a significant seasonal pattern, with franciscana sightings, particularly of calves, being more frequent during the summer ( p &lt; 0.05) and concentrated in nearshore estuarine zones. No dolphins were recorded at the southern reference site, reinforcing the hypothesis of the population's restricted distribution. Foraging was the predominant behavior observed (81% of behavioral records), also peak during the summer. The spatiotemporal overlap of this critical period for feeding and calf‐rearing with known threats, such as intensified artisanal gillnetting, highlights the vulnerability of this population. These findings provide key evidence for implementing targeted, seasonal management strategies to mitigate threats and enhance conservation outcomes for this unique and endangered dolphin population.