Due to its pelagic habits and its distribution in the southern oceans, not much is known about the life history of L. cruciger. To date little research has been done on this species. The measurements used in this account are from a small sample size. Future research will undoubtedly shed some light into the habits and life history of this mysterious dolphin.
There is no documentation of predation on these dolphins, however, they are likely preyed upon by killer whales, Orcinus orca. Like many aquatic animals, these dolphins are countershaded. Countershading is widely thought to be an antipredator adaptation, as a light underbelly is difficult to see from below, and a darker dorsal surface is less readily detected from above.
Known Predators:
Hourglass dolphins are small, robust, dolphins with a unique black and white color pattern. Pigmentation patterns vary greatly among L. cruciger individuals, but the sexes are monomorphic.
Hour glass dolphins have highly recurved, falcate dorsal fins with highly keeled tailstocks. The color pigmentation resembles that of an hourglass pattern for which the species gets its common name. It was first described by Qouy and Gaimard in 1824 and was called “cross bearer”.
These dolphins have homodont dentition with 53-69 conical-shaped teeth. The dental formula is 26-34 teeth in the upper jaw with 27-35 teeth in the lower jaw.
The dorsal side is all black with the white flank patches extending up to the keel of the tailstock. The sides are mostly black, marked with two variable white patches. The first (thoracic) patch begins behind the rostrum, extending above the eye and ends mid flank just before the dorsal fin. The rear (flank) patch starts behind the dorsal fin and extends to the tailstock. The two patches may or may not connect below the dorsal fin. The ventrum is mostly white from the rostrum to the tail flukes, which are black. The beak and eyes are outlined with black pigmentation.
The maximum length for L. cruciger is not known, as there are only nine records for this species. The average length of five females was 157.1 cm; 174.5 cm for three males and a third specimen of unknown gender was 155 cm. This measurement was taken from the snout to the tail fluke notch. These records would suggest that males are larger, however not enough data have been recorded to make such an assessment.
The weights of three specimens were recorded. One male weighed 94.0kg and two females weighed 73.5kg and 88.2kg. These data are also consistent with the notion that males of the species are larger than females, but with a sample of so few individuals, no generalizations can be drawn.
These dolphins can easily be distinguished south of the Antarctic convergence. They are the only small dolphin species with a dorsal fin found below this point. Above the convergence they may be confused with dusky dolphins, L. obscurus, and Peale's dolphins, L. australis
Range mass: 73.5 to 94 kg.
Average length: 157.1-174.5 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
The lifespan of L. cruciger is not known, however it may be similar to other species within its genus. The Atlantic white-sided dolphin, L. acutus, can live 27 years and the Pacific white-sided dolphin, L. obliquidens, can live up to 46 years in the wild.
Widely distributed throughout their range, L. cruciger is rarely seen near shore and prefers the colder waters of the open ocean. Surface water temperatures range between -0.3 degrees Centigrade (C) and 7.0 degrees C with 71% of the sightings occurring between 0.1 degrees C and 0.3 degrees C. The warmest recorded surface temperature associated with this species was 13.4 degrees C
Habitat Regions: temperate ; polar ; saltwater or marine
Aquatic Biomes: pelagic
Hourglass dolphins, Lagenorhynchus cruciger, are a truly pelagic species of dolphin. They are found throughout the southern oceans of the world and are circumpolar in their distribution. They range between 43 degrees south (S) and 67 degrees S and are most often associated near the Antarctic convergence. The farthest northern sighting of this species was off of the coast of Chile, 33 degrees 40' S
Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )
Hourglass Dolphins feed primarily on fish, squid (Onychoteuthidae and Enoploteuthidae), and crustaceans. Squid beaks from these families were found in the stomach of one specimen, and the remains of Krefftichtys andersonii, a mesopelagic lantern fish were found in another. They are often seen feeding in large congregations near the surface, which attract albatross, petrels and other sea birds. Researchers will often focus in on these large aggregations of birds to locate L. cruciger.
Animal Foods: fish; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )
The niche of hourglass dolphins is not known. They are social animals and will often travel and feed with other whales and dolphins. Based upon their diet, L. cruciger are most likely secondary or tertiary level consumers. They therefore may play some role in regulating prey populations.
Hourglass dolphins are not commercially harvested, but some are taken annually along with Dusky Dolphins, to be used as crab bait by local fishermen in Chile. Increasing ecotourism in the Antarctic also allows for further observations of this species.
Positive Impacts: ecotourism ; research and education
There is no known negative impact of this species on humans.
Currently L. cruciger is not listed as threatened or endangered; rough population estimates for the species are greater than 140,000. They are not exploited commercially and attempts to bring them into captivity have never been made. This is most likely due to the distribution of the species and the remoteness of the species' range. A few specimens were collected during commercial whaling operations for scientific research. Accidental by-catches from commercial fisheries are limited. Only four dolphins have been reported as having been caught in fish nets, and an additional three specimens were found stranded with severe net scars on their bodies.
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: least concern
There are no recorded data on communication for this species. However, it is likely that like all odontocetes that have been studied, they communicate with high frequency sounds. They are likely to have some tactile and visual communication as well.
Communication Channels: visual ; tactile ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
The mating behavior of these animals is not known.
There are very limited data on reproduction for this species. One female that was 183 cm in length was nearing sexual maturity. Two males that measured 174 cm and 187 cm in length were sexually mature. The age of these animals was not known.
There is some information on reproduction in other memebers of the genus Lagenorhynchus. Study of L. obscurus females killed in Peruvian fisheries indicates that the gestation period is about 12.9 months, and that most births occur late in the Southern Hemisphere winter (August-October). A lactation period of 12 months and an interbirth interval of 28.6 months are also recorded. In L. acutus, nursing last for about 18 months, and young become independant around the age of two years. There is generally only one offspring per pregnancy, but one female of this genus was recorded as having two embryos. Young are 90 to 125 cm in length at birth.
Breeding season: The breeding season of this species has not been recorded.
Average number of offspring: 1.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous
Females nurse their young, who are able to swim along with their mothers from birth. In other memebers of the genus for which data have been collected, lactation can last from 12-18 months. Other information on parental care is lacking for these animals.
Parental Investment: precocial ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female)
The Hourglass Dolphin – so named after the white hourglass pattern along its sides.This small, robust dolphin was first described in1824by Quoy and Gaimard and was also called ‘cross bearer’.For the Latin aficionados, it is calledLagenorhynchus cruciger.
Hourglass dolphins occupy the surface waters of the Antarctic and sub-Antarctic.This dolphin is sorarethat it is the only cetacean to be described solely on feedback from witnesses.From the dozen of hourglass dolphins that have been formally examined, these dolphins grow up to 1.8 meters in length and weigh between90 – 120 kgs.
Hourglass dolphins typicallyfeedon fish, squid and crustaceans.The stomach contents of one specimen even had lantern fish.Hourglass dolphins are often seen feeding in large congregations near the surface.These congregations attract seabirds and researchers typically locate these dolphins by focusing on large groups of seabirds.
These dolphins are social animals.They are typically travelling in a small or large group.Hourglass dolphins are known to change course to bow ride along ships and large whales.There are no records of predation on this species but it is assumed that orcas are most likely to prey on them.It is thought that thecounter-shadingof hourglass dolphins protects them from predation – their lighter coloured belly blends in with the light when viewed from below and their dark back blend with the dark water when viewed from above.
According to theIUCN Red List, hourglass dolphins are a species of Least Concern. This species is widespread and abundant.No threats for this species have been identified for hourglass dolphins.
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The hourglass dolphin (Lagenorhynchus cruciger) is a small dolphin in the family Delphinidae that inhabits offshore Antarctic and sub-Antarctic waters.[3] It is commonly seen from ships crossing the Drake Passage, but has a circumpolar distribution.
The species was identified as a new species by Jean René Constant Quoy and Joseph Paul Gaimard in 1824 from a drawing made in the South Pacific in 1820.[4] It is the only cetacean to have been widely accepted as a species solely on witness accounts.
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.[5] For this reason, it was colloquially known by whalers as a "sea cow"[6] (although it does not belong to the taxonomic order Sirenia) or "sea skunk".[5] 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 or cross pattée.[5] 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 is the only cetacean of comparable size and comparable coloration with overlapping distributions that lives as far south.[7] 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.[8]
An adult male is about 1.8 meters (5.9 feet) in length and weighs over 90 kilograms (about 200 lbs).[4][9] Juvenile females range from 1.6 to 1.8 meters (5.2 to 5.9 ft) in length and weigh from 70 to 90 kg (150 to 200 lb).[4] 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.[10]
The range is circumpolar from close to the Antarctic pack ice to about 45°S.[3] The northernmost confirmed sightings are 36°S in the South Atlantic Ocean and 33°S near Valparaíso, Chile, in the Pacific.[11] Sightings have been made most commonly from the south of New Zealand, around the South Shetland Islands[12] and off Tierra del Fuego, Argentina.[11]
Hourglass dolphins are often seen in smaller groups up to 10–15 individuals,[7] though groups of up to 100 have been observed.
They share feeding grounds with other cetaceans such as pilot whales, minke whales and southern right whale dolphins and are regularly seen with fin whales.[7] 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, polychaete worms, and various (unrecorded) species of squid and small fish.[13]
The species was first named Delphinus cruciger by Quoy and Gaimard (1824) after their sighting in January 1820.[4] Lesson and Garnot (1827) named another dolphin with two white patches on the sides Delphinus bivittatus.[4] 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).[4] Though it is traditionally placed in the genus Lagenorhynchus, molecular analyses suggest the species is more closely related to the right whale dolphins and dolphins of the genus Cephalorhynchus[14][15] and it has been suggested that it should be moved to a new genus Sagmatias.[16][15] The taxonomic relationship with the genus Cephalorhynchus (which includes, among others, Hector's dolphin) is further supported by the similarity of the echolocation signals to the signals used by Cephalorhynchus-species.[10]
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.[17] This is the only abundance estimate of hourglass dolphins to date.
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).[18] They are also listed in Appendix II of the Convention on International Trade in Endangered Species (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 on the IUCN Red List.[1]
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 distribution.
The species was identified as a new species by Jean René Constant Quoy and Joseph Paul Gaimard in 1824 from a drawing made in the South Pacific in 1820. It is the only cetacean to have been widely accepted as a species solely on witness accounts.
