Social and environmental drivers of foraging behavior in Guiana dolphins (Sotalia guianensis) in Northeastern Brazil

Abstract

Understanding how environmental and anthropogenic factors influence foraging behavior is essential to assess the vulnerability of coastal dolphin populations. We investigated the foraging dynamics of Guiana dolphins (Sotalia guianensis) in Praia do Madeiro Bay (Northeastern Brazil), focusing on both the frequency and collective structure of foraging events in relation to temporal, spatial, and boat-related variables. A total of 488 foraging events were recorded between March and June 2008, covering all daylight hours, tidal stages, and bay zones. A negative binomial model showed that foraging frequency was significantly lower under engine-on conditions, decreased seasonally from March to June 2008, and peaked during early morning hours. A complementary binomial model revealed that the probability of collective foraging decreased in some zones and later in the season, but increased when prey performed escape jumps. Boat presence also tended to enhance group coordination when engines were turned off. Together, these results indicate that S. guianensis flexibly adjusts its activity and coordination patterns in response to environmental cues and local vessel dynamics. The strong influence of boat traffic on both foraging frequency and coordination underscores the species’ sensitivity to human disturbance and highlights the need to regulate tourism activities within key feeding habitats.