Social and community structure of striped dolphins in a semienclosed Mediterranean embayment

Abstract

Descriptions of social structure of a species or population help to understand the processes that shaped its social system, and such knowledge can be valuable in terms of conservation planning. While striped dolphins Stenella coeruleoalba are among the most abundant cetacean species worldwide, and the most abundant in the Mediterranean Sea, their social and community structure is poorly known. This study investigates the association patterns of a population inhabiting the Gulf of Corinth, Greece. A total of 501 individuals were photo-identified across 7 years (2011–2017). Groups were significantly larger (M = 44.7, SD = 46.3) than those studied to date in other Mediterranean areas. Association analyses in SOCPROG relied on the time and position metadata of dorsal fin photographs. Results indicated a single community characterized by nonrandom associations and a loose clustering of individuals (best division into clusters corresponded to an association index of 0.02). The high degree of social cohesion may result in part from geographic isolation within a semienclosed basin. This information can inform management action to protect a demographically isolated population classified as Endangered in the IUCN Red List, within a European Union Site of Community Importance regarded as an Important Marine Mammal Area (IMMA).