The hourglass dolphin (''Lagenorhynchus cruciger'') is a small dolphin in the family

Delphinidae Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the ...

that inhabits offshore

Antarctic The Antarctic ( or , American English also or ; commonly ) is a polar region around Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica, the Kerguelen Plateau and other ...

and

sub-Antarctic The sub-Antarctic zone is a region in the Southern Hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° and 60° south of the Equator. The subantarctic region includes many islands ...

waters. It is commonly seen from ships crossing the

Drake Passage The Drake Passage (referred to as Mar de Hoces Hoces Sea"in Spanish-speaking countries) is the body of water between South America's Cape Horn, Chile and the South Shetland Islands of Antarctica. It connects the southwestern part of the Atla ...

, but has a

circumpolar distribution A circumpolar distribution is any range of a taxon that occurs over a wide range of longitudes but only at high latitudes; such a range therefore extends all the way around either the North Pole or the South Pole. Taxa that are also found in isolat ...

. The species was identified as a new species by

Jean René Constant Quoy Jean René Constant Quoy (10 November 1790 in Maillé, Vendée, Maillé – 4 July 1869 in Rochefort, Charente-Maritime, Rochefort) was a French naval surgeon, zoologist and anatomist. In 1806, he began his medical studies at the school of naval ...

and

Joseph Paul Gaimard Joseph Paul Gaimard (31 January 1793 – 10 December 1858) was a French naval surgeon and naturalist. Biography Gaimard was born at Saint-Zacharie on January 31, 1793. He studied medicine at the naval medical school in Toulon, subsequent ...

in 1824 from a drawing made in the South Pacific in 1820. It is the only

cetacean Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel them ...

to have been widely accepted as a species solely on witness accounts.

Description

The hourglass dolphin is colored black on top and white on the belly, with white patches on the sides and sometimes variations of dark grey. For this reason, it was colloquially known by whalers as a "sea cow" (although it does not belong to the taxonomic order Sirenia) or "sea skunk". Each flank has a white patch at the front, above the beak, eye and flipper, and a second patch at the rear. These two patches are connected by a thin white strip, creating, loosely speaking, an hourglass shape; hence the common name of the dolphin. The scientific name ''cruciger'' means "cross-carrier" and refers to the area of black coloration, which, viewed from above, vaguely resembles a

Maltese cross The Maltese cross is a cross symbol, consisting of four " V" or arrowhead shaped concave quadrilaterals converging at a central vertex at right angles, two tips pointing outward symmetrically. It is a heraldic cross variant which developed f ...

or cross pattée. There have been no verified sightings of calves and their coloration remains unknown. In its usual range the dolphin is easily identifiable. The

southern right whale dolphin The southern right whale dolphin (''Lissodelphis peronii'') is a small and slender species of cetacean, found in cool waters of the Southern Hemisphere. It is one of two species of right whale dolphin (genus ''Lissodelphis''). This genus is char ...

is the only cetacean of comparable size and comparable coloration with overlapping distributions that lives as far south. The absence of a dorsal fin in right whale dolphins, in contrast to the generally tall and curved dorsal fin of hourglass dolphins makes confusion of the two species very unlikely. The dorsal fin in hourglass dolphins is variable and the curvature may be particularly pronounced in older animals. The hourglass dolphin has disk-shaped vertebrae and other inclined processes which gives them higher stability. An adult male is about 1.8 meters (5.9 ft) in length and weighs over 90 kilograms (about 200 lbs). Juvenile females range from 1.6 to 1.8 meters (5.2–5.9 ft) in length and weigh from 70 to 90 kilograms (154–200 lbs). Males are thought to be slightly smaller and lighter than females, although the small number of specimens does not permit a firm conclusion. Like all species of dolphins, they use echolocation to find food.

Geographic range and distribution

The range is

circumpolar Circumpolar may refer to: * Antarctic region ** Antarctic Circle ** the Antarctic Circumpolar Current ** Subantarctic ** List of Antarctic and subantarctic islands ** Antarctic Convergence ** Antarctic Circumpolar Wave ** Antarctic Ocean * Arctic ...

from close to the Antarctic

pack ice Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.).Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag. Unlike fast ice, which is "fasten ...

to about 45°S. The northernmost confirmed sightings are 36°S in the South Atlantic Ocean and 33°S near

Valparaíso Valparaíso (; ) is a major city, seaport, naval base, and educational centre in the commune of Valparaíso, Chile. "Greater Valparaíso" is the second largest metropolitan area in the country. Valparaíso is located about northwest of Santiago ...

, Chile, in the Pacific. Sightings have been made most commonly from the south of

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

, around the

South Shetland Islands The South Shetland Islands are a group of Antarctic islands with a total area of . They lie about north of the Antarctic Peninsula, and between southwest of the nearest point of the South Orkney Islands. By the Antarctic Treaty of 195 ...

and off

Tierra del Fuego Tierra del Fuego (, ; Spanish for "Land of the Fire", rarely also Fireland in English) is an archipelago off the southernmost tip of the South American mainland, across the Strait of Magellan. The archipelago consists of the main island, Isla G ...

, Argentina.

Behavior

Hourglass dolphins are often seen in smaller groups up to 10–15 individuals, though groups of up to 100 have been observed. They share feeding grounds with other cetaceans such as

pilot whales Pilot whales are cetaceans belonging to the genus ''Globicephala''. The two extant species are the long-finned pilot whale (''G. melas'') and the short-finned pilot whale (''G. macrorhynchus''). The two are not readily distinguishable at sea, ...

minke whales The minke whale (), or lesser rorqual, is a species complex of baleen whale. The two species of minke whale are the common (or northern) minke whale and the Antarctic (or southern) minke whale. The minke whale was first described by the Danish na ...

and

s and are regularly seen with

fin whale The fin whale (''Balaenoptera physalus''), also known as finback whale or common rorqual and formerly known as herring whale or razorback whale, is a cetacean belonging to the parvorder of baleen whales. It is the second-longest species of cet ...

s. Hourglass dolphins frequently bow-ride waves from ships and baleen whales. Examinations of the stomach contents of the few specimens indicate they eat

mantis shrimp Mantis shrimp, or stomatopods, are carnivorous marine crustaceans of the order Stomatopoda (). Stomatopods branched off from other members of the class Malacostraca around 340 million years ago. Mantis shrimp typically grow to around in lengt ...

polychaete worms Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are m ...

, and various (unrecorded) species of

squid True squid are molluscs with an elongated soft body, large eyes, eight arms, and two tentacles in the superorder Decapodiformes, though many other molluscs within the broader Neocoleoidea are also called squid despite not strictly fitting t ...

and small fish.

Taxonomy

The species was first named ''Delphinus cruciger'' by Quoy and

Gaimard Joseph Paul Gaimard (31 January 1793 – 10 December 1858) was a French naval surgeon and naturalist. Biography Gaimard was born at Saint-Zacharie on January 31, 1793. He studied medicine at the naval medical school in Toulon, subsequent ...

(1824) after their sighting in January 1820. Lesson and Garnot (1827) named another dolphin with two white patches on the sides ''Delphinus bivittatus''. Throughout the 19th and early 20th centuries, scientists have given the hourglass dolphin various synonyms, including ''Phocoena crucigera'' (Philippi, 1893), ''Electra crucigera'' (Gray, 1871), and ''Lagenorhynchus clanculus'' (Gray, 1846; 1849; 1850; 1866). Though it is traditionally placed in the genus ''

Lagenorhynchus ''Lagenorhynchus'' is a genus of oceanic dolphins in the infraorder Cetacea, presently containing six extant species. However, there is consistent molecular evidence that the genus is polyphyletic and several of the species are likely to be move ...

'', molecular analyses suggest the species is more closely related to the right whale dolphins and dolphins of the genus ''

Cephalorhynchus ''Cephalorhynchus'' is a genus in the dolphin family Delphinidae. Extant species It consists of four species: The species have similar physical features—they are small, generally playful, blunt-nosed dolphins—but they are found in distin ...

'' and it has been suggested that it should be moved to a new genus ''

Sagmatias ''Sagmatias'' was a genus of Dolphin, dolphins, defined in 1866 by Edward Drinker Cope with Peale's dolphin as type species, described as ''Sagmatias amblodon''. It has been proposed to resurrect the genus to include four species of oceanic dolph ...

''. The taxonomic relationship with the genus ''Cephalorhynchus'' (which includes, among others,

Hector's dolphin Hector's dolphin (''Cephalorhynchus hectori'') is one of four dolphin species belonging to the genus '' Cephalorhynchus''. Hector's dolphin is the only cetacean endemic to New Zealand, and comprises two subspecies: ''C. h. hectori'', the more n ...

) is further supported by the similarity of the echolocation signals to the signals used by ''Cephalorhynchus''-species.

Population status

Sighting surveys were conducted in 1976–77 and 1987–88. Abundance was estimated to be 144,300 individuals, based on line transect sightings in January 1977 and January 1988 in northern Antarctic waters. This is the only abundance estimate of hourglass dolphins to date.

Conservation status

The hourglass dolphin is covered by the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region ( Pacific Cetaceans MOU). They are also listed in Appendix II of the

Convention on International Trade in Endangered Species CITES (shorter name for the Convention on International Trade in Endangered Species of Wild Fauna and Flora, also known as the Washington Convention) is a multilateral treaty to protect endangered plants and animals from the threats of interna ...

(CITES). Although they have not been studied extensively, there are no known major threats to hourglass dolphins, and the species is listed as

Least Concern A least-concern species is a species that has been categorized by the International Union for Conservation of Nature (IUCN) as evaluated as not being a focus of species conservation because the specific species is still plentiful in the wild. T ...

on the

IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biol ...

References

External links

*
''Lagenorhynchus cruciger'' – Hourglass Dolphin
Species Profile and Threats Database, Australian Government Department of the Environment and Energy
OBIS SEAMAP hourglass dolphin species profile
Duke University {{Taxonbar, from=Q301018 Mammals of Argentina Mammals of Chile Mammals of Patagonia Fauna of Antarctica Cetaceans of the Southern Ocean

hourglass dolphin The hourglass dolphin (''Lagenorhynchus cruciger'') is a small dolphin in the family Delphinidae that inhabits offshore Antarctic and sub-Antarctic waters. It is commonly seen from ships crossing the Drake Passage, but has a circumpolar dis ...

Lagenorhynchus