Lagenorhynchus australis (Peale, 1848)

Russell A. Mittermeier & Don E. Wilson, 2014, Delphinidae, Handbook of the Mammals of the World – Volume 4 Sea Mammals, Barcelona: Lynx Edicions, pp. 410-526 : 490

3.

Peale’s Dolphin

Lagenorhynchus australis

French: Dauphin de Peale / German: Schwarzkinndelfin / Spanish: Delfin austral

Other common names: Black-chinned Dolphin, Southern White-sided Dolphin

Taxonomy. Phocaena australis Peale, 1843 ,

“South Atlantic Ocean, off the coast of Patagonia,” Argentina.

Taxonomy of Lagenorhynchus is currently in dispute. Recent molecular analyses have revealed that the genus is not monophyletic. L. australis and L. cruciger appear to be most closely related to dolphins in the genus Cephalorhynchus and may be reassigned to Cephalorhynchus or to another genus ( Sagmatias ) in the near future.

Monotypic.

Distribution. Coastal waters of S South America from ¢.33° S in the Pacific Ocean and c.38° Sin the Atlantic Ocean, and S into Drake Passage (c.59° S) and Falkland Is.

Descriptive notes. Total length up to 220 cm (males) and up to 210 cm (females); weight up to 115 kg. Neonates are 98-130 cm long. Peale’s Dolphin has robust body shape and short, poorly defined beak. Dorsal fin and flippers are falcate with pointed tips. Dorsal area is dark gray to black, and most of the belly is white. There is pale grayto-white patch on upper posterior flanks stretching from base of flukes along tailstock to just in front of dorsal fin. This patch tapers anteriorly and fades into the dark color of back. There is another pale gray-to-white patch on lower anterior flanks extending from eye to middle body, tapering and fading posteriorly. Most of face is dark gray to black. A black band distinguishes white belly from rest of body. Ventral white area on chest extends onto flanks, slightly behind flippers in a manner reminiscent of “armpit” patches on species of Cephalorhynchus . Young Peale’s Dolphins are paler and more muted in color than adults. There are up to 37 pairs of teeth on upper jaw and up to 34 pairs on lower jaw.

Habitat. Most abundant in coastal waters, particularly around islands and over continental shelves. Peale’s Dolphins are also common in sheltered near-shore areas such as bays, inlets, and fjord entrances. Waters less than 20 m deep are preferred, but they have been observed in waters up to 300 m deep. In some areas, Peale’s Dolphins are closely association with coastal kelp beds. Several sightings of what appeared to be Peale’s Dolphins have been made in the Indo-Pacific Ocean, and these may be an undescribed form, subspecies, or species.

Food and Feeding. Stomach contents of only a few Peale’s Dolphins have been examined, and what is known of preferred prey comes mostly from kelp habitats. Documented prey species include pink cusk-eel (Genypterus blacodes), Argentine red shrimp (Pleoticus muelleri), Patagonian squid ( Doryteuthis gahi), hagfish (Myxine australis ), Patagonian cod (Salilota australis ), Patagonian grenadier ( Macruronus magellanicus), and southern red octopus (Enteroctopus megalocyathus). Peale’s Dolphin is known to feed among kelp beds, sometimes picking small cephalopods directly off the kelp fronds.

Breeding. Little is currently known about the life history and reproductive biology of Peale’s Dolphin. Breeding peaks during southern summer and autumn in October-April. Female sexual maturity is reached when individuals are 193-210 cm in length and c.13 years old.

Activity patterns. Dives of Peale’s Dolphin typically last between three seconds and 1-5 minutes and average 28 seconds. A typical dive pattern consists of one longer dive followed by three shorter dives. Peale’s Dolphins will bow-ride and behave energetically, frequently breaching acrobatically and playing in coastal surf. Echolocation clicks can be either broadband (5-12 kHz) or narrowband (1-2 kHz).

Movements, Home range and Social organization. Groups of Peale’s Dolphin usually consist of 2-30 individuals, but group sizes of more than 100 individuals have been seen. Peale’s Dolphin has been observed in mixed-species groups with Commerson’s Dolphin ( Cephalorhynchus commersonii ) and Risso’s Dolphin ( Grampus griseus ). They appear to be year-round residents in near-shore waters of the Strait of Magellan, but in the southern reaches of the Strait, they may be slightly more abundant during summer, a pattern possibly related to birthing. There are seasonal inshore—offshore movements off Tierra del Fuego; Peale’s Dolphins move inshore during summer, likely following migrating prey species, and move offshore during winter.

Status and Conservation. CITES Appendix II. Classified as Data Deficient on The IUCN Red List. There are currently no abundance estimates or population trend data for Peale’s Dolphin, and there are no data on stock or subpopulation structure. Peale’s Dolphins are harpooned in unknown numbers throughout Chilean waters for use as bait in crab traps, particularly in the Strait of Magellan and Tierra del Fuego. Target species of these traps, the southern king crab (Lithodes santolla) and false southern king crab (Paralomis granulosa), have been overfished, so fewer dolphins may be killed for bait. Crabbing companies also now supply bait to fishermen. Nevertheless, there has been no formal assessment on the impact of this fishery on Peale’s Dolphins. Small cetaceans have been protected from direct catch in Chile since 1977, but enforcement is poor. Direct catch in Argentine waters was stopped in the 1980s. Peale’s Dolphins are occasionally entangled in fishing nets throughout the southern parts of their distribution in Chile and Argentina. In the northern Pacific Ocean, incidental catch appears to be minimal, but there are reports of entanglement in nets that are set to deter pinnipeds (seals) from salmon and mussel farms around Isla Chiloe. Association of Peale’s Dolphins with kelp forests may also make them vulnerable to habitat loss and degradation, particularly from aquaculture development.

Bibliography. Boy et al. (2011), Brownell, Crespo & Donahue (1999), Goodall (2009a), Hammond et al. (2008c), Jefferson et al. (2008), May-Collado & Agnarsson (2006), Pinedo et al. (2002), Schiavini et al. (1997), Viddi & Lescrauwaet (2005).

Figures

On following pages: 3. Peale’s Dolphin (Lagenorhynchus australis); 4. Hourglass Dolphin (Lagenorhynchus crucigen; 5. Pacific White-sided Dolphin (Lagenorhynchus obliquidens); 6. Dusky Dolphin (Lagenorhynchus obscurus); 7. Irrawaddy Dolphin (Orcaella brevirostris); 8. Australian Snubfin Dolphin (Orcaella heinsohni).

Distribution. Coastal waters of S South America from ¢.33° S in the Pacific Ocean and c.38° Sin the Atlantic Ocean, and S into Drake Passage (c.59° S) and Falkland Is.