Southernmost records of bottlenose dolphins, Tursiops truncatus

Abstract

Bottlenose dolphins (Tursiops spp.) are cosmopolitan animals widely distributed in waters of both hemispheres. The taxonomy of Tursiops has long been controversial, with over 20 specific names being published, and subspecies and inshore/offshore forms being proposed. In the southwestern South Atlantic, subspecies T. truncatus truncatus and T. truncatus gephyreus were proposed for specimens along the coasts of Brazil, Uruguay, and Argentina. Sightings of bottlenose dolphins are common along the coast of Argentina as far south as the Province of Chubut (ca. 46°S). Here, we summarize and discuss the southernmost records of bottlenose dolphins. We cannot make inferences about the species or subspecies to which these animals belong given the small number of specimens.Future studies of external measurements, pigmentation, DNA, and isotopes from both sides of the continent should help clarify the situation off southern South America. Furthermore, research is needed to explore a possible link between an effect of general global warming and the Tursiops specimens found this far south. The sighting and specimens described here, at 53°S-nearly 55°S, are the southernmost records for the genus and extend the range of the species in the southern South Atlantic.

Report of the Working Group on the Distribution of Tursiops truncatus in the Southwest Atlantic Ocean

“…Bottlenose dolphins have been observed from Samborombón Bay (province of Buenos Aires) to the southern province of Chubut, although occasional records exist further south in the provinces of Santa Cruz and Tierra del Fuego (Goodall, 1989;Bastida et al, 2007;Goodall et al, 2011). The earliest record of bottlenose dolphins for this region was based on the capture of two individuals reported by Lahille (1908) in the La Plata River.…”

“…The common bottlenose dolphin (Tursiops truncatus Montagu, 1821), hereafter bottlenose dolphin, is a cosmopolitan species distributed throughout tropical and temperate coastal and pelagic waters, between 45°N and 54°S 1 (Goodall et al, 2011). Studies on this species in the Southwest Atlantic Ocean (SWAO) have intensified in the last two decades, albeit with irregular effort.…”

Report of the Working Group on Taxonomy and Stock Identity of bottlenose dolphins in the Southwest Atlantic Ocean

“…Cremer et al, 2009) and Argentina (Vermeulen and Cammareri, 2009;Goodall et al, 2011), also revealed that the genus Tursiops presents a more complex variation than a simple latitudinal differentiation in the SWAO.…”

“…A comprehensive understanding of the taxonomic status and population structure of bottlenose dolphins in this region depends on a more detailed analysis of individuals from coastal and oceanic zones along different latitudes. In addition, for a complete understanding of taxonomy and stock discreteness of bottlenose dolphins in the southernmost areas of Argentina (between 53°S and nearly 55°S), future genetic studies on both ocean basins off South America will be necessary, since a connection between Atlantic and Pacific animals is possible via the southern fjords and channels of South America (Olavarria et al, 2010;Goodall et al, 2011).…”

“…This is almost the same size of the largest skulls reported from the coasts of Uruguay (564.0 to 607.0mm, n=6) and Buenos Aires Province, Argentina (565.0 to 607.0mm, n=8) (Barreto, 2000). In addition, the CBL of the animals from the provinces of Chubut and Tierra del Fuego (Argentina), in the southernmost areas, varied from 564.0 to 584.0mm (n=2) and from 509.0 to 524.0mm (n=5), respectively 9 (Goodall et al, 2011).…”