Spatio-Temporal Patterns and Limited Co-Occurrence Among Dolphin Species in the Bay of Algeciras–Gibraltar

This study examines spatio-temporal patterns of dolphin species in a coastal ecosystem located in the Bay of Algeciras–Gibraltar (southern Spain), a highly anthropogenic coastal system influenced by a submarine canyon and exposed to intense anthropogenic pressure. Between 2017 and 2020, spatial and temporal relationships between short-beaked common dolphins (Delphinus delphis), striped dolphins (Stenella coeruleoalba), and bottlenose dolphins (Tursiops truncatus) were analysed. A solitary female bottlenose dolphin (Billie) was considered separately as an individual case due to its distinct behavioural patterns. Georeferenced data showed that distances between sightings of T. truncatus and subsequent observations of the other species ranged from 261 to 12,000 m, with temporal intervals spanning from 33 s to 5 h 38 min. Short temporal overlaps (≤300 s) were infrequent. These results indicate limited spatio-temporal overlap between D. delphis, S. coeruleoalba, and T. truncatus within the study area. While no statistically significant relationships were detected in the applied models, the observed patterns provide a descriptive quantitative characterisation of species distribution and co-occurrence in a highly anthropogenic coastal system. Given that D. delphis is classified as Endangered in the western Mediterranean and that both D. delphis and S. coeruleoalba are frequently observed with calves, these patterns may be relevant for understanding habitat use and potential implications for conservation. Overall, this study provides a detailed empirical characterisation of spatio-temporal patterns among sympatric dolphin species in this coastal system, highlighting the need for further research using targeted analytical approaches to assess interspecific dynamics.