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Overview

Brief Summary

The Hourglass dolphin according to MammalMAP

The Hourglass Dolphin – so named after the white hourglass pattern along its sides.   This small, robust dolphin was first described in 1824 by Quoy and Gaimard and was also called ‘cross bearer’.  For the Latin aficionados, it is called Lagenorhynchus cruciger.

Hourglass dolphins occupy the surface waters of the Antarctic and sub-Antarctic.  This dolphin is so rare that 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 between 90 – 120 kgs.

Hourglass dolphins typically feed on 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 the counter-shading of 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 the IUCN 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.

For more information on MammalMAP, visit the MammalMAP virtual museum or blog.

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Distribution

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 )

  • Goodall, R. 1997. Review of Sightings of the Hourglass Dolphin, *Lagenorhynchus cruciger*, in the South American Sector of the Antarctic and Sub-Antarctic. Report of the International Whaling Commission, 47: 1001-1013.
  • Leatherwood, S., R. Reeves. 1983. The Sierra Club Handbook of Whales and Dolphins. San Francisco, CA: Sierra Club Books.
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Range Description

Hourglass dolphins are distributed in a circumpolar pattern in the higher latitudes of the southern oceans (Goodall 1997; Goodall et al. 1997; Brownell and Donahue 1999). They range to the ice-edges in the south, but the northern limits are not well-known (they are found to at least 45°S, although some occasionally reach 33°S). The most southerly sightings are from near 68°S, in the South Pacific (Goodall 1997; Brownell and Donahue 1999). This is the only small delphinid species regularly found south of the Antarctic Convergence.
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Southern ocean to ice-edge in the south
  • UNESCO-IOC Register of Marine Organisms
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Physical Description

Morphology

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

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Ecology

Habitat

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

  • Brownell Jr., R., M. Donahue. 1999. Hourglass Dolphin, *Lagenorhynchus cruciger*. Pp. 121-135 in S Ridgeway, H Harrison, eds. Handbook of Marine Mammals: Vol. 6: The Second Book of Dolphins and Porpoises. San Diego: Academic Press.
  • Goodall, R., A. Baker, P. Best, M. Meyer, N. Miyazaki. 1997. On The Biology of the Hourglass Dolphin, *Lagenorhynchus cruciger* (Quoy and Gaimard, 1824). Report of the International Whaling Commission, 47: 985-999.
  • Klinowska, M. 1991. Dolphins, Porpoises and Whales of the World. The IUCN Red Data Book. Gland, Switzerland and Cambridge, U.K.: IUCN.
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Habitat and Ecology

Habitat and Ecology
Normally seen far out to sea, L. cruciger has also been observed in fairly shallow water near the Antarctic Peninsula and off southern South America. It occurs within 160 km of the ice edge in some areas in southern part of the range (Jefferson et al. 1993). Most sightings of these dolphins are in an area around the Antarctic Convergence, between South America and Macquarie Island. The species seems to prefer surface water temperatures between 0.6° - 13°C (mean 4.8 °C; Goodall 1997) or even down to -0.3°C (Goodall 2002).

The stomach contents of the five specimens of hourglass dolphins that have been examined contained small fish (including myctophids), squids, and crustaceans. They often feed in aggregations of seabirds and in plankton swarms.

Systems
  • Marine
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oceanic
  • UNESCO-IOC Register of Marine Organisms
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Depth range based on 42 specimens in 1 taxon.
Water temperature and chemistry ranges based on 42 samples.

Environmental ranges
  Depth range (m): 0 - 0
  Temperature range (°C): -1.400 - 10.570
  Nitrate (umol/L): 9.068 - 30.310
  Salinity (PPS): 33.336 - 34.425
  Oxygen (ml/l): 6.247 - 8.077
  Phosphate (umol/l): 0.730 - 2.064
  Silicate (umol/l): 2.365 - 62.240

Graphical representation

Temperature range (°C): -1.400 - 10.570

Nitrate (umol/L): 9.068 - 30.310

Salinity (PPS): 33.336 - 34.425

Oxygen (ml/l): 6.247 - 8.077

Phosphate (umol/l): 0.730 - 2.064

Silicate (umol/l): 2.365 - 62.240
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Trophic Strategy

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 )

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Associations

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.

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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:

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Known predators

Lagenorhynchus cruciger is prey of:
Orcinus orca

This list may not be complete but is based on published studies.
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Known prey organisms

Lagenorhynchus cruciger preys on:
non-insect arthropods
Actinopterygii
Mollusca
Crustacea

This list may not be complete but is based on published studies.
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Life History and Behavior

Behavior

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

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Life Expectancy

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.

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Reproduction

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)

  • Goodall, R., A. Baker, P. Best, M. Meyer, N. Miyazaki. 1997. On The Biology of the Hourglass Dolphin, *Lagenorhynchus cruciger* (Quoy and Gaimard, 1824). Report of the International Whaling Commission, 47: 985-999.
  • Nowak, R. 1999. Walker's Mammals of the World, Vol. 2, Sixth edition. Baltimore and London: The Johns Hopkins University Press.
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Conservation

Conservation Status

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

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IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B.

Reviewer/s
Rojas-Bracho, L. & Smith, B.D. (Cetacean Red List Authority)

Contributor/s

Justification
The species is widespread and abundant and no threats have been identified.

History
  • 1994
    Insufficiently Known
    (Groombridge 1994)
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Population

Population
In the only abundance estimate for this species, Kasamatsu and Joyce (1995) combined data gathered in sighting surveys conducted from 1976/77 to 1987/88 to produce an abundance estimate of 144,300 (CV =17%) for waters south of the Antarctic convergence.

Population Trend
Unknown
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Threats

Major Threats
There are no known major threats to this species.
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Management

Conservation Actions

Conservation Actions
The species is listed in Appendix II of CITES.
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Relevance to Humans and Ecosystems

Benefits

There is no known negative impact of this species on humans.

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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

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Risks

IUCN Red List Category

Least Concern (LC)
  • IUCN (2008) Cetacean update of the 2008 IUCN Red List of Threatened Species.
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Wikipedia

Hourglass dolphin

Hourglass dolphin!<-- This template has to be "warmed up" before it can be used, for some reason -->

The hourglass dolphin (Lagenorhynchus cruciger[2]) is a small dolphin in the family Delphinidae that inhabits Antarctic and sub-Antarctic waters.

The dolphin has rarely been seen. It was identified as a new species by Qouy and Galmard 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. By 1960, despite decades of whaling in the Southern Ocean, only three specimens had been recovered. As of 2010 only 6 complete and 14 partial specimens had been examined. Further information was obtained from 4 strandings and boats which searched for the dolphins in areas rarely visited by ships.

Though it is traditionally placed in the genus Lagenorhynchus, recent molecular analyses indicate that the hourglass dolphin is actually more closely related to the dolphins of the genus Cephalorhynchus.

Contents

Physical description

The hourglass dolphin is colored black and white and for this reason was colloquially known by whalers as a "sea cow". 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 and hence the common name of the dolphin. The scientific name cruciger is Latin for "cross-carrier". This refers to the area of black coloration, which, viewed from above, vaguely resembles a Maltese cross or cross pattée.

In its usual range the dolphin is easily identifiable. Only the southern right whale dolphin is of comparable size and lives as far south. The right whale dolphin does not have a dorsal fin, so the two species are easily distinguished. The fin considerably varies across individuals. It is generally tall and curved, and the curve may be particularly pronounced in older animals.

A fully grown adult is about 1.8 meters (6 ft) length and weighs 90–120 kilograms (200–260 lb). Males are thought to be slightly smaller and lighter than females, although the small number of specimens does not permit a firm conclusion.

Population and distribution

The range is circumpolar from close to the Antarctic ice pack to about 45°S. The most northerly confirmed sightings were 36°S in the South Atlantic Ocean and 33°S near Valparaíso, Chile, in the Pacific. Sightings have been made most commonly from the south of New Zealand, around the South Shetland Islands and off Tierra del Fuego, Argentina. The species is unlikely to be particularly densely populated close to these lands.

One survey estimated the population size at more than 140,000 individuals.[citation needed]

Behavior

Hourglass dolphins tend to move in groups of about 5 to 10. One International Whaling Commission study recorded a group of 60.

They share feeding grounds with other cetaceans such as sei, pilot, bottlenose and minke whales and southern right whale dolphins. They are regularly seen with fin whales. Whalers who were hunting these much larger animals used hourglass dolphins as "look-outs" to aid them in their hunt. Hourglass dolphins are keen bow-wave riders.

Examinations of the stomach contents of the few specimens indicate they eat various (unrecorded) types of squid and small fish.

References

  1. ^ Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. (2008). Lagenorhynchus cruciger. In: IUCN 2008. IUCN Red List of Threatened Species. Downloaded on 24 March 2009. Database entry includes a brief justification of why this species is of least concern
  2. ^ Froese, Rainer, and Daniel Pauly, eds. (2006). "Lagenorhynchus cruciger" in FishBase. April 2006 version.
  • LeDuc, R.G., Perrin, W.F., Dizon, A.E. (1999). Phylogenetic relationships among the delphinid cetaceans based on full cytochrome b sequences. Marine Mammal Science 15, 619–648.
  • May-Collado, L., Agnarsson, I. (2006). Cytochrome b and Bayesian inference of whale phylogeny. Molecular Phylogenetics and Evolution 38, 344-354.
  • National Audubon Society: Guide to Marine Mammals of the World ISBN 0-375-41141-0
  • Encyclopedia of Marine Mammals ISBN 0-12-551340-2
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