Home Sweet Home? Wide-Ranging Movements of Socially Stable Resident Delphinids (Globicephala macrorhynchus)

Abstract

 Movement patterns of delphinid populations are generally known to occur within specific geographical areas; with the exception of the killer whale (Orcinus orca). Additionally, knowledge of wide-ranging migrations in these animals are mainly attributed to individual records with limited information on their social structure, residency status or purpose of migration. Here, a comparison of photographic-identification catalogues of short-finned pilot whales (Globicephala macrorhynchus) from the two most isolated archipelagos of the North Atlantic (Madeira and Azores) shows that five well-marked adult animals have made a round-trip movement, of no less than 2000 km. These delphinids belong to the main resident pod in Madeira, where they present long-term site fidelity and were photographed in the Azores during an apparent stop (of at least 10 days), most likely for breeding or feeding purposes. The analysis of the association patterns of these individuals shows that they were sighted together on multiple occasions during the entire study period, suggesting that they are members of a cohesive unit. These findings broaden our understanding on these animals’ home ranges and suggest caution when establishing residency status in delphinids