As like as two peas in a pod
(28-01-10) Peale’s dolphin and dusky dolphin are two very similar species that are often mistaken. They only differ from the fact that dusky dolphin has a greyish white stripe on both sides, which separates into two to the anterior part of body. Its face is not dark and the back of its dorsal fin is whitish.
There are many examples of animal very alike in Nature, so it is easy to mistake them. It is the case of these two dolphins of the same family: Lagenorhynchus australis or Peale’s dolphin, and Lagenorhynchus obscurus or dusky dolphin, whose habitats coincide in South America.
The scientific name Lagenorhynchus australis comes from the Greek word lagenos (bottle or flask) and rhynchos (nose or beak), referring to dolphin’s little defined nose. The word australis comes from Latin and refers to the southern geographical distribution. 
The English name Peale’s dolphin refers to Titian Peale, the first one to describe this species in 1848, from a picture made during a North American expedition to the Patagonia. In Spanish it is known as “delfín de Peale”, among other names, and the same happens in German (Peale Delphin) and in French (Dauphin de Peale).
Peales’s dolphin is the biggest and strongest dolphin of the genus Lagenorhynchus. Males can be 2.18 m. long and females 2.10 m. When they born, the can be almost one meter long. Their average weight is 100 kg.
They are grey or black in their back, pectoral, dorsal and caudal fins, as well as the head, lips and throat. Their breast and belly are pale, although is becomes darker in the genital area. A white area in the insertion of the pectoral fins stands out. They have a short beak not very well defined.
Peale’s dolphin’s calves are lighter 
From the caudal peduncle and forward they have a light gray band tapering when it reaches the dorsal fin and which ends in a thin line that stretches almost to the vent.
Dorsal fin, well developed and slightly falcate is inserted in the middle of the body. Calves are lighter and their colour is more uniform, light grey.
The skull of species Lagenorhynchus that inhabit our seas are similar to each other. Peale’s dolphin has between 27 and 33 pairs of teeth in each jaw.
Its distribution is restricted to waters in thee south of South America. The northern limit of the area is Valparaiso (33° S) in the Pacific coasts and to 38° S in the Atlantic coasts. To the south they are found until Cape Horn and the Burdwood Bank (around 57°). A specimen of Peale’s dolphin has been found in the southern town of Miramar, in Buenos Aires province (38 ° 17'S).
The further north sightings in the Atlantic were recorded at 42° S, however, Peale’s dolphins are more common in the south of Caleta Olivia and Cape Blanco (47° S). They are often observed in the province of Santa Cruz, Tierra del Fuego, Magellan Strait, Beagle Channel and waters near the Falkland Islands.
They shelter and eat in algae forests
Their habitat is basically in the coasts, frequenting capes, creeks, bays, channels and fjords (such as the ones in Tierra del Fuego and south of Chile), and they are associated to algae forests (Macrocystis pyrifera) where they find shelter and food.
Food is usually coastal, generalist and possibly opportunistic. The records show that they usually hunt fishes like the Tapole codling (Salilota australis), the pink cusk-eel (Genypterus blacodes), the haddock (Merluccius hubssi), the blue grenadier (Macroronus magellanicus), the silverside (Austroatherina sp.), the Patagonian blennie (Eleginops maclovinus), as well as squid (Loligo gahi), octopus (Enteroctopus megalocyathus), shrimp (Pleoticus muelleri) and small mysidacea crustaceans.
Clear migrations have not been recorder. We know very little about the reproduction of this species: births occur during the spring, and females come into sexual maturity when they reach 1.90 m in length.
In the area of Cabo Vírgenes the group composition varies between 1 and 13 individuals. However, in other areas bigger groups up to 30 and 100 animals were observed. They have been recorded breathing and dive frequency from 3 to 4 per minute with an interval of apnoea of 1 to 130 seconds.
It is very common to see interactions among these dolphins with other species, such as the Commerson's dolphins (Cephalorhynchus commersonii), the southernrRight whale (Eubalaena australis), the great grebe (Podiceps major), the Magellanic penguin (Spheniscus magellanicus), the rock shag (Phalacrocorax magellanicus), the Kelp gull (Larus dominicanus) and the South American sea lion (Otaria flavescens).
Community hunting techniques
Peale’s dolphin use different cooperative food techniques, and it is common to see fast swimming on the surface with many water displacement, specimens swimming in a circle, high, low, sideways jumping, and tail strikes that are for stunning preys and forcing them to move in a certain direction, and this way round them up.
During the 70’s and the 80’s there were important catches of the Peale’s dolphin to use it as bait for traps of king crabs (Lithodes antarctica) and false king crabs (Paralomis granulosa), in the South of Argentine and Chile. Between 1977 and 1979 iit is estimated that in that area they were caught more than 4,000 dolphins for traps, mainly Commerson's dolphins and Peale’s dolphin. In Chile some specimens were used for human consumption.
Fortunately, conservation measures were taken in both countries to reduce catches. Some specimens of this dolphin have been caught incidentally in gill nets or trammel nets used for fishing bass and other species.
Main threats for this species are overexploitation, mortality in fishing nets, the increasing petroleum activity and ignorance. Peale’s dolphin is included in Appendix II in CITES (Convention on International Trade in Endangered Species of Wild Fauna and Flora), and the IUCN (the International Union for Conservation of Nature) considers it an insufficient recognised species. The Argentinian Libro Rojo considers it of low risk (RB), conservation dependent.
The dusky dolphin has a pale face
The dusky dolphin (Lagenorhynchus obscurus), also belongs to the family Delphinidae and within the genus Lagenorhynchus. In Spanish it is known as “delfín oscuro”, and “delfín de Fitzroy”, in French “dauphin sombre”, in German “schwarzdelphin”. It can reach up to 2.1 meters and size up to 90 kg.
It is often mistaken for the Peale’s dolphin (Lagenorhynchus australis), but, unlike this one, the grayish white stripe on the flanks has splits in two peaks to the anterior part of body, its face is dark and the back of its dorsal fin is whitish.
Its distribution is only in the Southern Hemisphere. It can be seen in South America, New Zealand, Kerguelen Islands and South Africa. In South America, it is more frequently observed from the Peninsula Valdes to Buenos Aires province, in the Atlantic, and from Valparaiso (Chile) to Peru in the Pacific.
It is a gregarious species with coastal habits. It is extremely acrobatic: jumps over 4 meters tall that can be repeat again and again (up more than 15 consecutively) have been observed. These jumps can be clean or dolphins can hit water with body parts when re-entering the water.
They can be seen associated with other cetacean species (such as southern right whale and common dolphin), with a hair sea lions and several species of seabirds.
The dusky dolphin is accidentally caught in fishing nets and illegally harpooned (in Peru) to use their meat and blubber as bait in shark fishing. IUCN considers it as Data Deficient (DD), and this species is included in Appendix II of CITES.
Text: Guadalupe Romero
