Abstract
Social organization is an important feature of the behavior of most delphinids, including the rough-toothed dolphin (Steno bredanensis), although, even in social dolphins, specific circumstances may lead to solitary behavior. In these situations, a solitary dolphin may shift to interacting with humans. Between November 2018 and April 2019, we obtained seven records of the occurrence of a solitary juvenile rough-toothed dolphin in Sepetiba Bay, southeastern Brazil, within an area inhabited by a resident population of Guiana dolphins, Sotalia guianensis. The solitary dolphin occupied a small home range located in an inner area of the bay, close to a port and industrial installations. This area is known to be inhabited by shoals of mullet (Mugilidae) and is not visited frequently by the resident Guiana dolphins. The solitary rough-toothed dolphin emitted three types of vocalization: pulsed calls (N = 9), echolocation click trains (N = 12), and whistles (N = 3), and spent most of its activity time interacting with humans (42%) and foraging (32%). The area occupied by this dolphin, together with its low vocalization rate, suggest the avoidance of agonistic interactions with local Guiana dolphins. The behavior pattern presented by the solitary rough-toothed dolphin indicates the third stage of development of friendly solitary dolphin behavior. At this stage, a management plan is urgently required to avoid the negative consequences of the human-dolphin interaction.
Best,
Israel Maciel