Abstract
Research on the ecology of sympatric dolphins has increased worldwide in recent decades. However, many dolphin associations such as that between common dolphins (Delphinus delphis) and dusky dolphins (Lagenorhynchus obscurus) are poorly understood. The present study was conducted in the San Matías Gulf (SMG) ecosystem (North Patagonia, Argentina) where a high diet overlap among both species was found. The main objective of the present work was to explore the niche overlap of common and dusky dolphins in the habitat and temporal dimensions. The specific aims were (a) to evaluate the habitat use strategies of both species through a comparison of their group attributes (social composition, size and activity), and (b) to evaluate their habitat preferences and habitat overlap through Environmental Niche modeling considering two oceanographic seasons. To accomplish these aims, we used a historic database of opportunistic and systematic records collected from 1983 to 2011. Common and dusky dolphins exhibited similar patterns of group size (from less than 10 to more than 100 individuals), activity (both species use the area to feed, nurse, and copulate), and composition (adults, juveniles, and mothers with calves were observed for both species). Also, both species were observed travelling and feeding in mixed-species groups. Specific overlap indices were higher for common dolphins than for dusky dolphins, but all indices were low, suggesting that they are mainly segregated in the habitat dimension. In the case of common dolphins, the best habitats were located in the northwest of the gulf far from the coast. In the warm season they prefer areas with temperate sea surface and in the cold season they prefer areas with relatively high variability of sea surface temperature. Meanwhile, dusky dolphins prefer areas with steep slopes close to the coast in the southwestern sector of the gulf in both seasons.
Highlights
Research on the ecology of sympatric dolphins has increased worldwide in recent decades [1– 3]
The environmental niche overlap was higher for common dolphins than for dusky dolphins, and they were more overlapped in the warm season than in the cold one
From previous studies we knew that common dolphins and dusky dolphins presented a considerable but asymmetrical diet overlap in the San Matías Gulf (SMG)
Summary
Research on the ecology of sympatric dolphins has increased worldwide in recent decades [1– 3] This is in part because dolphins, together with primates, are the mammalian groups with the most highly elaborated brains and with most ecologically and socially complex populations [4, 5]. The estimation of overlap indices through the outputs of Environmental Niche Models (ENMs) allows to take advantage of historical and/or occasional data of species presence [6–8]. This is important considering the complexity and coast of data collection for dolphin ecology in marine environments (the main reason of information gaps about dolphin associations in many world regions) [1, 9, 10]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
