Site Fidelity and Residency Patterns of Rough‐Toothed Dolphins ( Steno bredanensis ) in Madeira Island Using Photo‐Identification

ABSTRACT

The rough‐toothed dolphin ( Steno bredanensis ) is distributed in warm waters worldwide, yet its spatial ecology remains poorly understood, especially in the Eastern North Atlantic. This study presents the first assessment of site fidelity and residency patterns for the species in this region, using year‐round photo‐identification data collected in Madeira Island between 2016 and 2024. A total of 1092 captures from 637 individuals showed that 62.5% were captured only once. The remaining individuals showed that 26.1% were recaptured intra‐annually and 19.6% interannually (mean = 3 captures, SD = 1, range = 2–10), with a maximum recapture interval of 8 years. The proportion of distinctive marked dorsal fins was 51.1% (SD = 6.4%). Lagged Identification Rates, based on a model incorporating emigration and reimmigration, estimated that 28 individuals were present in the study area during the summer (July–August), with a mean stay of 6.4 days and an absence of 626 days. The Standardized Site Fidelity Index indicated low association (mean = 0.0057, SD = 0.0065) with the area. Overall, rough‐toothed dolphins appear to be mainly transients or occasional visitors, suggesting high mobility and limited temporal association with the southern waters of Madeira, mainly during the summer. These findings provide new insights for guiding conservation strategies for rough‐toothed dolphins in the Macaronesia biogeographic region.