Mesoplodon grayi

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 native
• atlantic ocean atlantic ocean
  • native native
• pacific ocean pacific ocean
  • native native

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

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.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike
• ornamentation ornamentation

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 .

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous 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 precocial
• female parental care 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

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.

Behavior

Pods of M. grayi have been spotted in the waters all over the southern hemisphere, but there is no information on the movements of particular pods or individuals. No attempts to track or radio-collar these animals have been reported.

Recorded sightings of Gray's beaked whales are usually pods of between 4 and 10 animals. Some authorities indicate that these animals may form larger pods than other beaked whales, and mass strandings of 28 animals have been noted. Single animals have been observed, but they are rare. There have been many unconfirmed reports that M. grayi raises its white beak above the water just prior to surfacing.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• migratory migratory
• social social

Home Range

Information on the home range size of M. grayi is unavailable.

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 tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• choruses choruses

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

• Primary Diet
• carnivore carnivore
  • molluscivore molluscivore

• Animal Foods
• fish
• mollusks

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 cryptic

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.

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.

Economic Importance for Humans: Negative

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

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.

Additional Links

Encyclopedia of Life

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Arthur Wang (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

References

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 .

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.

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.

2000. "Cetacea" (On-line). Accessed February 09, 2004 at http://www.cetacea.org .