The long-beaked common dolphin of the eastern Pacific Ocean: Taxonomic status and redescription of Delphinus bairdii

Neritic, long-beaked common dolphins have been described as species distinct from the more oceanic and globally distributed short-beaked species, Delphinus delphis, although recent molecular studies have challenged this view. In the eastern North Pacific (ENP), the taxonomic status of the long-beaked (bairdii) form has been controversial since its original description in 1873, and has vacillated between species, subspecies, and geographic forms several times. It is currently provisionally viewed as a subspecies of Delphinus delphis, D. d. bairdii. To clarify this situation, we reviewed the literature and conducted additional analyses using both newly obtained genetic and cranial morphometric data sets. The results indicate that there are diagnostic differences in skull morphology and coloration between the eastern Pacific long-and short-beaked forms, and near-perfect diagnosability in mitochondrial DNA. These differences, along with indications of ecological distinctions, including important differences in life history parameters and reproductive timing, indicate that these forms are well on their way down separate evolutionary pathways. As such, we consider them to be distinct species in the eastern Pacific. The long-beaked species is referable to Delphinus bairdii Dall, 1873, and is redescribed as such herein.