Overview

Brief Summary

Biology

The elusive nature of Gray's beaked whale, together with its far offshore habitat and apparent rarity, mean that little is known about the biology and behaviour of this marine species (5) (6). Like other member of the genus, it is likely to feed mainly on cephalopods such as squid (1) (5) (10), with most prey being caught in deep water, below depths of 200 metres, and believed to be swallowed whole (3) (5). Some fish may also be taken (5) (10), and prey is thought to be sucked into the mouth with the aid of a muscular tongue and throat pleats, which allow the mouth floor to be distended (5). The teeth of Gray's beaked whale are no longer needed for feeding, and in the adult male these have evolved into fighting weapons, with males often bearing long, white tooth scars, which are thought to be evidence of dominance battles (3) (5) (10). Most Gray's beaked whales are seen alone or in pairs or small groups, though a mass stranding of 28 animals has suggested that this species may be more social than other beaked whales (3) (6) (9). Very little information is available on the breeding behaviour of Gray's beaked whale (10), but, as in all cetaceans, females give birth to a single calf (5).
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Description

One of the more easily distinguished members of its genus, Gray's beaked whale has a particularly long, slender snout, or 'beak', which is white in adults, with a straight mouthline, and which is often raised up out of the water when the whale surfaces (3) (5) (6). The spindle-shaped body is dark bluish-grey to black on the upper surface, with a paler underside, white patches in the genital region and sometimes on the forehead, and often bears white oval scars from the bites of cookie-cutter sharks (2) (3) (6). The dorsal fin is small and set quite far back on the body, the tail is unnotched, and the small flippers fit into depressions in the body, reducing water resistance when the whale is swimming (3) (5) (7). Juveniles have dark patches around the eyes and on top of the head, lighter bellies, and a shorter and darker beak than the adult (3) (8). Mature male Gray's beaked whales possess a single pair of functional teeth, which are triangular in shape and located midway along the lower jaw (2) (3) (9). These teeth project up, outside of the mouth, and can be seen when the mouth is closed (5) (10). In the female, these teeth are much smaller and do not usually erupt above the gums (3) (6) (10). Both sexes also have a row of small, non-functional teeth in the upper jaw (3) (9).
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Distribution

Geographic Range

The general distribution of Gray's beaked whales, Mesoplodon grayi , is in the oceans of the southern hemisphere, south of 30 degrees latitude. Original sightings were off the coast of New Zealand and Eastern Australia east to Argentina and Chile. However, recent sightings near South Africa, north to Madagascar, and in the Indian Ocean east to Australia confirm its circumpolar home range. There has been one confirmed live animal sighting in the northern hemisphere, off the coast of The Netherlands, but there have been no other indications of a North Atlantic population (IUCN, 1991).  Though there are nineteen species in the Family Ziphiidae (Beaked Whales), they are rarely seen and poorly studied. There is no reliable information on migratory habits, if any, of this species.

Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native )

  • Evans, P. 1987. The Natural History of Whales & Dolphins. New York, New York USA: Facts on File, Inc.
  • Klinowska, M., J. Cooke. 1991. Dolphins, Porpoises, and Whales of the World. Switzerland and Cambridge, U.K.: IUCN The World Conservation Union.
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Range

Gray's beaked whale is found throughout cool, temperate waters of the Southern Hemisphere, with records from Antarctic and sub-Antarctic waters, as well as around New Zealand, southern Australia, South Africa, Argentina, Chile and Peru (1) (3) (11). However, as with all members of this group, Gray's beaked whale is rarely sighted and often difficult to identify out at sea, and information on its distribution is largely based on strandings (5) (7). There is a single record of a stranding in the Netherlands, but it is thought that this was an unusual occurrence, outside of the species' normal range (1) (3) (7). Many sightings occur around New Zealand and the Chatham Islands (1) (3), though this may merely be due to more intensive recording efforts here (9).
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Physical Description

Morphology

Physical Description

Gray’s Beaked whales, like all members of Ziphiidae, are medium sized whales with a distinct beak. They are 5.0 to 6.0 m in length and weigh around 5 tons (10,000 pounds). M. grayi is distinct from all other beaked whales (except for Tasmacetus shepherdi) in that it does not lack upper teeth; rather, it has a row of 17 to 22 teeth lining each side of the upper jaw.

The coloration pattern of M. grayi is similar to other beaked whales, with dark brown to gray on the back and flanks, and light gray to white on the underside. The beak is characteristically white or light colored with white flecks extending to the throat. There are also conspicuous white markings around the navel, genitals, and anal regions.

One of the most conspicuous features of members of the genus Mesoplodon is the single pair of enlarged triangular tusks in the lower jaw. The location of these tusks is set farther back in the mouth than in other beaked whales. The exact function of these tusks is unknown, but the pattern of scarring on the head and body of examined individuals indicates that fighting may occur, most likely for mates . Some Mesoplodon have a hardened bone in their skulls, acting like a shield while fighting. These tusks were originally thought to erupt only in males. However, more recent information shows that the tusks erupt in both sexes. Beached females with erupting tusks, have been discovered recently with high frequency.

Average mass: 5000 kg.

Range length: 5.5 to 6.0 m.

Sexual Dimorphism: sexes alike; ornamentation

  • MacLeod, C. 2000. Species recognition as a possible function for variations in position and shape of the sexually dimorphic tusks of Mesoplodon whales. Evolution, 56/6: 2171-2173.
  • MacLeod, C. 2002. Possible functions of the ultradense bone in the rostrum of Blainville's beaked whale (Mesoplodon densirostris). Canadian Journal of Zoology, 80:1: 178-184.
  • Culik, B. 2002. "Mesoplodon grayi" (On-line). Convention on Migratory Species (CMS). Accessed August 08, 2004 at http://www.cms.int/reports/small_cetaceans/data/m_grayi/m_grayi.htm.
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Ecology

Habitat

The particular waters M. grayi occupies are not well known. Animals are generally spotted in waters deeper than 2000 m, but animals frequent shallower waters and have often been found beached in New Zealand.

Range depth: 2000 to 0 m.

Habitat Regions: temperate ; tropical ; saltwater or marine

Aquatic Biomes: pelagic ; coastal

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Gray's beaked whale typically inhabits deep waters, far from shore (1) (5) (10). Although some sightings have been made in shallower waters (8), these are usually of sick animals coming in to strand (1).
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Trophic Strategy

Food Habits

Beaked whales of the genus Mesoplodon eat squid almost exclusively, usually members of the families Ommastrephidae, Octopoteuthidae, Enoploteuthidae, and Neoteuthidae. Mesoplodon may also feed on deep-sea and mesopelagic fish (Lampanyctus, Scopelogadus, Cepola), but they are likely to be only opportunistic prey; squid make up the great majority of the diet.

Animal Foods: fish; mollusks

Primary Diet: carnivore (Molluscivore )

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Associations

Ecosystem Roles

The evolutionary development of dentition in mesoplodont whales and their nearly exclusive diet of squid, indicate that there must be a strong ecological relationship between these organisms. The highly specialized tongue and reduced teeth allow the whales to use suction to capture their prey. The stomach remains of mesoplodont whales almost always contains squid species smaller than 500 g, which contrasts sharply with other beaked whales (genera Hyperoodon and Ziphius) whose diet consists mainly of squid averaging 1000 g in weight (CMS, 2003). This information indicates that Mesoplodon occupies a dietary niche separate from other beaked whales.  The preference for and effectiveness at capturing squid suggests that mesoplodont whales strongly impact the squid population.

Species Used as Host:

  • Data Unknown

Mutualist Species:

  • Data Unknown

Commensal/Parasitic Species:

  • Data Unknown

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Predation

Natural preadators of Gray's Beaked whales are unknown. The natural coloration pattern (dark on the dorsal side, lighter on the belly) makes these animals harder to see from above (where they blend in with darker water below) and from below (where they blend in with lighter water above it).

This species is not known to be commercially hunted, but the possibilty that individuals have been taken by fishing operations cannot be excluded. However, the known population of M. grayi generally resides outside of most commercial fishing operations and the impact of these operations is probably limited.

Anti-predator Adaptations: cryptic

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Life History and Behavior

Behavior

Communication and Perception

The communication habits of M. grayi are unknown, but those of other whales have been well studied. Whales are famous for their combination of songs, squeals, grunts, clicks, and clacks. Because water serves as a much better transmission medium for sound than air, evolution has clearly centered on vocal communication rather than any other form. The timing of whale communications, along with their content, may signal position, identity, threats, or food to other members of a pod or to other pods.

The most common beaked whales, Blainville's Beaked whales, have been observed to use particular patterns of clicks when herding schools of prey, possibly to confuse them. It has been proposed that M. grayi uses similar methods, but further information is unavailable.

Some tactile communication most likely occurs between mates, as well as between mothers and their offspring. If the tusks of these animals are used in physical competition, as scarring patterns on the head indicate, this is another form of tactile communication which should be noted.

Females may signal their sexual readiness with chemical cues.

Communication Channels: tactile ; acoustic ; chemical

Other Communication Modes: choruses

Perception Channels: visual ; acoustic

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Life Expectancy

Lifespan/Longevity

There is no information on the lifespan of M. grayi and there have been no reports of attempts to keep any animals in captivity.

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Reproduction

Unfortunately, there is little information on the mating system of M. grayi. However, it is very likely that M. grayi follows similar patterns to other toothed whales (Odontoceti). M. grayi, like other toothed whales, does not show as distinct a seasonality in mating and birth as do the baleen whales; this is primarily due to the relatively warmer waters the toothed whales inhabit. Toothed whales live in small groups with very large ranges of thousands of square miles. It may be difficult for individuals to meet others of the opposite sex, so when they do, it is essential that the right signals are conveyed. Toothed whales are very social, and when pods meet there are physical changes in the female’s body to indicate to potential mates that she is ready. Though these exact signals are unknown, it is likely that a combination of both behavioral dance-like movements and hormones discharged through feces or urine serve as cues.

The courtship and mating rituals usually involve belly contact between the male and female. The pair may be interlocked vertically, or the male may swim upside-down underneath the female. There is also much play in the form of chases, breaching of the surface, and flipper contact. All these behavioral cues convey the readiness to mate.

Detailed information on the reproductive behavior of M. grayi is unavailable. The mother most likely give birth to a single calf. Gray’s beaked whales, like many whales, are most often seen in pods and highly social behavior has been observed. Often in these groups, females that don't have offspring of their own assist other females in the pod raise their calves. A calf likely remains by its mother’s side until it reaches maturity.

Although toothed whales occupying warm oceanic waters can breed throught the year, most breeding in the southern hemisphere is probably between October and December, and the young are born between February and March. Breeding grounds for similar species are often in shallower waters that are sheltered by bays or inlets. Seasonal movements from winter mating grounds to summer feeding grounds are common for other species but not confirmed for M. grayi.

Breeding interval: Unknown; Probably one calf per year.

Breeding season: Unknown; Probably between October and December

Average number of offspring: 1.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous

All cetacean species follow a similar pattern for parental investment. The mother nurses the young; she and the pod family teach newborn calves how to socialize, how to avoid preadators, and how to hunt. Specific information on M. grayi is unavailable.

Parental Investment: no parental involvement; precocial ; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Protecting: Female); extended period of juvenile learning

  • Evans, P. 1987. The Natural History of Whales & Dolphins. New York, New York USA: Facts on File, Inc.
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Conservation

Conservation Status

M. grayi is protected by the Marine Mammal Protection Act of 1972. These laws are a strict guideline protecting marine mammals and their habitats. For M. grayi in particular, there is not enough information to determine its appropriate conservation status. Original sightings were so rare that the animals were thought to be close to extinction, but the increasing number of reliable sightings suggests there is a larger, more stable population than believed.

IUCN Red List of Threatened Species: no special status

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Status

Classified as Data Deficient (DD) on the IUCN Red List (1) and listed on Appendix II of CITES (4).
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Threats

Although possibly not as rare as some other Mesoplodon species, there is currently no information available on the global abundance or population trends of Gray's beaked whale (1) (3) (5). Although not directly hunted (1) (5) (12), individuals may occasionally be killed by gillnets and long line fishing gear (1) (5) (10), and even in low levels this may pose a significant threat to the species (12). Other potential threats include trauma from loud, man-made sounds, such as those generated by military activities (1) (12), as well as plastic waste, which may be swallowed and cause death by blocking the whale's digestive tract (1). There is also evidence that individuals may occasionally be struck by boats (8). Gray's beaked whale may be vulnerable to ocean warming as a result of climate change, though the effects of such changes on the species are not yet known (1).
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Management

Conservation

Gray's beaked whale is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning international trade in this species should be carefully controlled (4). However, the lack of information on Gray's beaked whale means that research into its biology and abundance, as well as into the potential threats it faces, is desperately needed before appropriate conservation measures, if necessary, can be put into place (1) (9). Recent molecular studies (13) may help improve otherwise difficult species identification in this and other beaked whales, aiding research and helping to increase our knowledge of this poorly understood group of marine mammals.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

There are no known adverse affects of M. grayi on humans.

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Economic Importance for Humans: Positive

The instances of humans encountering M. grayi are so rare that it probably has little direct economic importance. Further information is unavailable.

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