Dolphins have long-lasting friendships and form cliques while shunning other groups. This is according to observations of bottlenose dolphins in the Gulf of Trieste in the northern Adriatic sea over a period of 9 years.
The dolphins formed mixed-sex clusters, including two main groups that enjoyed stable membership and long-lasting friendships. Both groups contained a core membership with extra tiers, while dolphins in one of the groups sometimes formed smaller factions.
Each group was connected by several dolphins which acted as social brokers, preventing complete cluster isolation. Overall the groups tended to avoid each other but shared particular areas of water by using them at different times.
“We were quite surprised by this. It is not uncommon for dolphins to segregate into different parts of the sea, but to have certain times of the day in which they gather is unusual,” says Tilen Genov at the University of St Andrews, who led the study.
The team believes that ecological constraints, such as the availability of prey, could explain the inclusion of older-looking dolphins into the social groups.”These animals may possess long-term knowledge needed to tackle such constraints and thus play a key role in their community,” wrote the researchers.
Journal reference: Marine Biolog, DOI: 10.1007/s00227-018-3450-8
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