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Mesoplodon layardiistrap-toothed whale

By Andrea Flohr

Geographic Range

Mesoplodon layardii tends to live in the cold temperate waters of the Southern Hemisphere. A majority of the sightings have been around Australia, New Zealand, and Tasmania, but there have also been sightings in South Africa, Namibia, the Falkland Islands, Argentina, Chile, and Uruguay. (Sekiguchi, et al., 1996; "Texas Marine Mammal Stranding Network", 2002)

Habitat

Strap-toothed whales are found in deep oceanic waters of the temperate to subantartic regions. They may use adjacent waters for feeding and calving. (Bannister, et al., 2001)

  • Range depth
    2000 (high) m
    6561.68 (high) ft

Physical Description

Adult strap-toothed whales weigh between 907 and 2,721 kg and are 5 to 6.2 m in length. Newborns tend to be 2.5 to 3 m in length,with and unknown weight.

These animals have a spindle-shaped body with a rounded to slightly bulging melon that ends in a long slender beak. The flippers are small, narrow, and rounded. The dorsal fin is set far past the body and is falcate in shape. ("Texas Marine Mammal Stranding Network", 2002; "The Whale and Dolphin Conservation Society", 2002)

The whales are mainly bluish-black to dark purplish in color with patches of white on the underside, between the flippers, on the beak, and in a band around the head. There are also black patches over the eyes and forehead. ("The Whale and Dolphin Conservation Society", 2002)

The most distinctive morphological characteristic of M. layardii is the single pair of mandibular teeth that are found only in adult males. These teeth curve over the upper jaw allowing the mouth to open only 11 to 13 cm. It is assumed that these teeth are used for intraspecific competition between males due to the high number of scars observed on the males. (MacLoed, 2000; Sekiguchi, et al., 1996)

  • Range mass
    907 to 2721 kg
    1997.80 to 5993.39 lb
  • Range length
    5 to 6.2 m
    16.40 to 20.34 ft

Reproduction

The mating system of M. layardii has not been observed.

Little is known about their reproductive behavior. It is thought that mating occurs in summer and calving occurs in summer to autumn after a 9 to 12 month gestation period. (Bannister, et al., 2001)

  • Breeding interval
    Strap-toothed whales breed once per year.
  • Breeding season
    Breeding apparently occurs in the summer.
  • Average number of offspring
    1
  • Range gestation period
    9 to 12 months

There have been no studies of parental care in M. layardii. However, groups consisiting of a single female with calf pairs are often observed. In general, newborn cetaceans are precocial. They are able to follow the mother from birth. Although the female nurses the offspring, the duration of lactation is not known for this species. The role of the male in parental care is likewize unknown. (Bannister, et al., 2001)

  • Parental Investment
  • no parental involvement
  • precocial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

Lifespan of M. layardii is unknown. However, members of other species in the genus are reported to have lived from 27 to 48 years. (Bannister, et al., 2001; Nowak, 1999)

Behavior

Strap-toothed whales tend to shy away from boats, therefore they are rarely seen in the wild. When they are observed it is reported that they slowly sink below the surface of the water and rise again 150 to 250 meters away. Sometimes an individual will perform a lateral roll, exsposing a single flipper. Typically the dives last 10 to 15 minutes. (Bannister, et al., 2001; "Texas Marine Mammal Stranding Network", 2002)

Home Range

The home range of these animals has not been reported.

Communication and Perception

The large tusks in adult males are presumably a form of visual or tactile communication. Other toothed whales also use echolocation. It is likely that there are some forms of accoustic communication within the species, also. (MacLoed, 2000)

Food Habits

Twenty-four species of oceanic squid, along with some deep sea fish make up the main diet of strap-toothed whales. Confusion and fascination surround the feeding habits of these whales due to the enlarged mandibular teeth in the males. At first they were thought to interfere with feeding, but it is now thought that they may act as "guide rails" to send food to the throat. Even this hypothesis is questioned because it is quite possible that M. layardii, like other beaked whales, suck food into their mouths, regardless if how far they can open their mouths. (Sekiguchi, et al., 1996)

  • Animal Foods
  • fish
  • mollusks

Predation

These whales may be prey for killer whales. (Bannister, et al., 2001)

Ecosystem Roles

Strap-toothed whales feed on a variety of marine organisms. they are therefore likely to have some impact on populations of these organisms. (Sekiguchi, et al., 1996)

Economic Importance for Humans: Positive

These animals are not reported to have any positive economic impact on humans.

Economic Importance for Humans: Negative

These animals are not reported to have any negative impacts on humans.

Conservation Status

Mesoplodon layardii is a species which is threatened by many things: possible entanglement in drift nets and other nets; competition from expanding fisheries, especially on squids; pollution leading to accumulation of DDT and PCBs in body tissues; and they are the most stranded Ziphiid in Australia. In 1982, the National Stranding Contigency Plan was designed to outline scientific objectives and appropriate biological/veterinary research activies for the stranded whales. (Bannister, et al., 2001)

Another focus for the conservation efforts lies in the development of objectives and agreements to protect cetaceans and their environment under federal and state laws. Strap-toothed whales are listed on Appendix II of CITES. (Bannister, et al., 2001)

Other Comments

There are many common names listed for M. layardii. The most frequently used are strap-toothed whale, strap-toothed beaked whale, and Layard's beaked whale. (Bannister, et al., 2001)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Andrea Flohr (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor), University of Wisconsin-Stevens Point.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

diurnal
  1. active during the day, 2. lasting for one day.
echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

tactile

uses touch to communicate

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

References

Texas A&M University-Corpus Christi. 2002. "Texas Marine Mammal Stranding Network" (On-line ). Accessed 11/04/02 at http://www.sci.tamucc.edu/tmmsn/29Species/MoreSpec/straptoothedwhale.html.

The Whale and Dolphin Conservation Society. 2002. "The Whale and Dolphin Conservation Society" (On-line ). Accessed 11/04/02 at http://www.wdcs.org.

Bannister, J., C. Kemper, R. Warnke. 2001. "The Action Plan for Australian Cetaceans" (On-line ). Accessed 11/04/02 at http://www.ea.gov.au/coasts/species/cetaceans/actionplan/whaleap5z.html.

MacLoed, C. 2000. Species Recognition as a Possible Function for Variations in Position and Shape of the Sexually Dimorphic Tusks of Mesoplodon Whales. Evolution, 54/6: 2171-2173. Accessed 12/03/02 at http://www.bioone.org.

Nowak, R. 1999. Walker's Mammals of the World, Sixth Edition. Baltimore and London: The Johns Hopkins University Press.

Sekiguchi, K., N. Klages, P. Best. 1996. The Diet of Strap-toothed Whales(Mesoplodon layardii). Journal of Zoology,London, 239/3: 453-463.

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