Stay here, but keep quiet: the effects of anthropogenic noise on Guiana dolphins (Sotalia guianensis) in southeastern Brazil

Abstract

Shipping is the principal source of anthropogenic noise in the aquatic soundscape of coastal areas.Noise can have temporary or permanent effects on the physiology, behavior, and ecology of the marine mammals and, as noise pollution is considered to be an important threat to Guiana dolphins (Sotalia guianensis), we focused on this question in the present study. We modeled the impacts of anthropogenic noise on the acoustic behavior and distribution of these dolphins. We considered the acoustic parameters and occurrence of Guiana dolphins as the response variables and Sound Exposure Levels (SEL) and environmental factors as the explanatory variables. The dolphins used noisier areas but communicated mainly in less noisy areas, given that anthropogenic noise levels induced a reduction in whistle rates.Although the dolphins did not appear to avoid the noisiest areas, their communication was impaired, and there may be areas in which communication is impracticable in this species.

Assessment of Body Condition in a Threatened Dolphin Population in an Anthropized Area in Southeastern Brazil

“…Foraging in areas occupied by vessels may mask dolphin communications, which are essential for the coordination of the group's movements when catching prey [55]. A previous study in Sepetiba Bay [17] found that Guiana dolphins communicated significantly less in noisier areas. Dolphins in poor condition may prefer to conserve energy by avoiding communication rather than spending more energy to increase vocalization emission rates, even if this may affect their feeding success [43].…”

“…The large proportion of individuals photo-identified in a poor condition is a preoccupying reflection of the health status of this dolphin population [3]. The poor condition of the dolphins is likely a consequence of the cumulative impacts on these animals over the past decade in Sepetiba Bay, resulting from overfishing, excessive tourism, and noise, chemical, and organic pollution [17,37]. It is important to note, however, that this dataset includes transient individuals, which may be less exposed to these impacts than the resident dolphins.…”

“…In general, this species does not form large aggregations over the long term, but rather at specific events, such as feeding at concentrated resources. Social groups range in size from two to 300 individuals, depending on the circumstances, such as prey availability, habitat quality, and intraspecific competition, which vary considerably among the habitats occupied by this species [10,[14][15][16][17].…”

Scientific communication and scientific literacy for the public perception of the importance of environmental quality for public health

“…In this scenario, strategic approaches that link science to aspects of daily life can be a powerful and useful instrument. Some basic examples include framing or relating climate change to air pollution (Hart and Feldman, 2021) or exploring how noise and water pollution affect the lives of marine animals, such as dolphins and other mammals inhabiting ecosystems near urban centers (Maciel et al, 2023;Alzola-Andres et al, 2024). Thus, incorporating media literacy and emphasizing real-world connections offers a pragmatic pathway forward.…”