UNVEILING THE ENIGMATIC NATURAL HISTORY OF MEDITERRANEAN COMMON DOLPHIN (DELPHINUS DELPHIS, LINNAEUS 1758): INSIGHTS FOR CONSERVATION CHALLENGES

The common dolphin (Delphinus delphis, Linnaeeus, 1785) is one of the most enigmatic species in the Mediterranean Sea. Once widely prevalent, it faced a significant decline across most of the basin by the late 1960s. The precise reasons and mechanisms behind this decline remain largely unknown or poorly understood. However, a range of potential causes has been identified, encompassing deliberate culling, accidental deaths in fishing gear, reduced prey availability, and habitat degradation. Present estimates derived from surveys and monitoring campaigns suggest either a complete absence or a near disappearance of common dolphins from areas historically known to harbor substantial populations. The International Union for Conservation of Nature has designated the Inner Mediterranean subpopulation of common dolphin as “Endangered”. We reconstructed the little-known natural history of this species using osteological museum finds from the last two centuries. The multidisciplinary approach consisting of genetic analysis on ancient DNA, geometric morphometry on skulls, and collagen stable isotope analysis, has enabled a better understanding of the ecology of the historical Mediterranean common dolphin population. The main findings of the research include: i) Incorrect taxonomic attributions in museum collections and historical literature represent a bias in the identification of Mediterranean dolphin species and in the knowledge of their demographic and ecological history over the past decades and centuries; ii) the molecular/morphometrical integrated approach permitted the successful species-specific identification of museum specimens and to highlight misidentifications and potential interspecific hybridization events between the rare Delphinus delphis and other more common species in the basin, such as Stenella coeruleoalba and Tursiops truncatus; iii) Results from stable isotope analysis (δ13C and δ15N) show different ecological and/or trophic patterns of Mediterranean common dolphin over time, indicating a possible shift in the ecological niche across the past centuries.