The taxonomy and distribution patterns of the common dolphins (genus Delphinus) are problematic among cetaceans and particularly complicated in the south-western Atlantic Ocean. On the basis of national collections, we found ten adult skulls of the genus Delphinus of Uruguayan origin. The two currently recognized species for the genus were identified based on craniometric measurements: the pelagic short beaked form (Delphinus delphis, N = 3) and the coastal long beaked form (Delphinus capensis, N = 4), although previous studies only recognized D. capensis for Uruguay. Three specimens could not be identified (Delphinus sp.) because of broken skull (2) and intermediate measures (1). This result is consistent with a recent review on the biogeography of the genus in the south-western Atlantic Ocean.

The short-beaked common dolphin (Delphinus delphis) is regarded as notably rare or absent from the northern North Sea, but recent evidence suggests a rising frequency of the species in these waters with increasing regional sea temperatures. The following paper documents the presence of D. delphis in the Moray Firth in north-east Scotland and provides the first evidence for the sustained occurrence of these delphinids in this region during the warmer summer months at least. Sightings were collated during systematic surveys of the outer Moray Firth between 2001 and 2009 by independent research teams from the CRRU and WDCS. A total of 13 encounters (with group sizes ranging from 2 to 450+ animals) were recorded with the species across this period, the first of which was in June 2006, with annual encounters being logged thereafter between the months of May and August from 2007 to 2009 inclusive. The animals were recorded in water depths of 51 to 209 m (mean depth: 88.6±42.2 m) and at a distance from shore of 5 to 32 km (mean distance: 16.6±8.0 km). New born calves were observed in June and July, and photographic recaptures of identifiable ‘marked’ adults were determined in 2009. The consistent presence of common dolphins in the outer firth post 2005 and the recapture of recognizable individuals suggest a comparatively recent colonization of these waters by the species over a relatively short period of time. The impacts resulting from such a range expansion upon the existing cetacean community and the subsequent implications for management are discussed.