American Cetacean Society - Los Angeles Chapter 
FREE Monthly Speaker Series 
Tuesday, September 25
at 7:30 p.m.

The long-beaked common dolphin of the eastern North Pacific: Is it a separate species or what?
by Thomas A. Jefferson, Clymene Enterprises

Part of the reason that the two forms of common dolphin are so difficult to tell apart in the field is that they are so closely related. Coastal, long-beaked common dolphins have been described as species that are distinct from the more oceanic, globally-distributed short-beaked species, Delphinus delphis, although recent studies have challenged this view. The taxonomic status of the long-beaked form found in the eastern North Pacific has been controversial since its original 1873 description, and has vacillated frequently among species, subspecies, and geographic forms. It is currently viewed as a subspecies of D. delphis, though the need for further work has been acknowledged. Tom Jefferson and colleagues reviewed the literature and analyzed relevant extensive molecular and cranial morphometric datasets. The preliminary results support previous findings of diagnostic differences in skull morphology and mitochondrial DNA (mtDNA) sequences between the long-and short-beaked forms in the eastern Pacific. These differences, along with evidence of ecological distinctions (including important differences in life history parameters, reproductive timing, and acoustics), indicate that the long-beaked form is on an evolutionary pathway independent of other common dolphins. This talk will discuss the latest research investigating the status of long- and short-beaked common dolphins off our coast.

Tom has been studying marine mammals since 1983, when he was an undergraduate student. His main interests are the development of marine mammal identification aids, and the systematics and population ecology of the more poorly-known species of dolphins and porpoises. Essentially all of his work since the 1980s has been related to conservation and management of marine mammals threatened by human activities. Since 1995, he has been working in Southeast Asia, and has traveled widely in the region. Tom’s primary research focused on the conservation biology, systematics, and ecology of Indo-Pacific humpback dolphin (Sousa chinensis) and Indo-Pacific finless porpoise (Neophocaena phocaenoides) populations and related species in Hong Kong and surrounding waters. He is involved in the conservation of the critically-endangered vaquita (Phocoena sinus), and on the taxonomy and population ecology of common dolphins (Delphinus spp.) among other projects. Tom co-authored Marine Mammals of the World: A Comprehensive Guide to Their Identification (2nd edition, Academic Press) with Marc Webber and Robert Pitman. His other interests include mountain biking, hiking, drums and percussion, outdoor photography, and wildlands preservation.