Pygmy right whale

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Pygmy right whale[1]
Caperea marginata 3.jpg
Pygmy right whale size.svg
Size compared to an average human
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Class: Mammalia
Infraorder: Cetacea
Family: Cetotheriidae
Subfamily: Neobalaeninae
(Gray, 1873)
Genus: Caperea
Gray, 1864
Species:
C. marginata
Binomial name
Caperea marginata
(Gray, 1846)
Cetacea range map Pygmy Right Whale.png
Pygmy right whale range
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The pygmy right whale (Caperea marginata) is a member of the cetotheres,[3] a family of baleen whales, which until 2012 were thought to be extinct; previously C. marginata was considered the sole member of the family Neobalaenidae.[4] First described by John Edward Gray in 1846, it is the smallest of the baleen whales, ranging between 6 metres (20 ft) and 6.5 metres (21 ft) in length and 3,000 and 3,500 kg in mass. Despite its name, the pygmy right whale may have more in common with the gray whale and rorquals than the bowhead and right whales.[4]

The pygmy right whale is found in the Southern Ocean in the lower reaches of the Southern Hemisphere, and feeds on copepods and euphausiids. Little is known about its population or social habits. Unlike most other baleen whales, it has rarely been subject to exploitation.

Taxonomy

During the 1839-43 voyage of James Clark Ross, naturalists found bones and baleen plates resembling a smaller version of the right whale. In his Zoology of the Voyage of HMS Erebus and Terror (1846), John Edward Gray described the new species, naming it Balaena marginata. In 1864, Gray established a new genus (Caperea) after receiving a skull and some bones of another specimen. Six years later, in 1870, he added the name Neobalaena. He soon realized the three species were one and the same: Caperea marginata[5] (caperea means "wrinkle" in Latin, "referring to the wrinkled appearance of the ear bone"; while marginata translates to "enclosed with a border", which "refers to the dark border around the baleen plates of some individuals").[6] In research findings published on December 18, 2012, paleontologist Felix Marx compared the skull bones of pygmy right whales to those of other extinct cetaceans, finding it to be a close relative to the Cetotheriidae, making the pygmy right whale a living fossil.[3][7]

In 2012, Italian palaeontologist Michelangelo Bisconti described Miocaperea pulchra, a first fossil pygmy right whale from Peru. This new genus differs from the living genus in some cranial details, but Bisconti's study confirmed the monophyly of the Neobalaenidae and he concluded that the rorqual-like features in C. marginata must be the result of parallel evolution. The presence of a fossil neobalaenid some 2,000 km (1,200 mi) north of the known range of C. marginata, suggests that environmental change has caused a southern shift in neobalaenid distribution.[8] A second, undescribed species was tentatively assigned to Neobalaenidae in 2012.[9]

Description

The pygmy right whale is rarely encountered and consequently little studied. However, it is known that it is by far the smallest of the baleen whales. Calves are estimated to be about 1.6 metres (5 ft 3 in) to 2.2 metres (7 ft 3 in) at birth (a 2 metres (6 ft 7 in) fetus was reported from a 6 metres (20 ft) female).[10] By the time they are weaned they may be about 3 metres (9.8 ft) to 3.5 metres (11 ft) long. It is believed they become sexually mature at about 5 metres (16 ft) and physically mature at about 6 metres (20 ft).[4] The longest male was a 6.1 metres (20 ft) individual which had stranded in Cloudy Bay, Tasmania, while the longest female was a 6.45 metres (21.2 ft) individual which had stranded in Stanley, Tasmania.[11] Pygmy rights can weigh as much as 3,430 kg[4]—a 6.21 metres (20.4 ft) female weighed 3,200 kg and a 5.47 metres (17.9 ft) male weighed 2,850 kg.[12] Gestation and lactation periods and longevity are all unknown. Part of the reason for the scarcity of data may be the relative inactivity of the whale, making location for study difficult. The blow is small and indistinct and the whale is usually a slow undulating swimmer, although capable of bursts of acceleration.

The coloring and shape of the pygmy right whale, dark gray dorsally and lighter gray ventrally, commonly with a pair of chevron-shaped lighter patches behind the eyes, is similar to that of the dwarf minke and Antarctic minke whales and at sea may easily be confused with these two species if the jaw and flippers are not carefully observed. The arched jawline is not as pronounced as other right whales and may not be sufficient to distinguish a pygmy right whale from a minke whale. The long, narrow cream-coloured baleen plates with a distinctive white gumline are the most effective discriminators. Unlike true right whales, pygmy rights do not have callosities. The dorsal fin is falcate (crescent-shaped) and located about three-quarters of the way along the back of the animal. Unlike the minke whales, occasionally the dorsal will not be seen on the whale surfacing. Like the minkes, though, it doesn't raise its flukes when it dives.

The skull and skeleton of the pygmy right whale is unlike those of any other extant whale: the supraoccipital shield extends farther posteriorly; the ear bone has a lateral wrinkle and is roughly square in outline. All seven cervical vertebrae are fused, and the pygmy right has only 44 vertebrae. The 18 pairs of ribs are broad and flat, and make up 39–45% of the vertebral column (compared to 33% in other mysticetes.)[4][13] Each thoracic vertebrae has a pair of huge wing-like transverse processes, many of which overlap. The dorsal end of the ribs are remarkably thin and almost fail to make contact with the transverse processes. The reduced tail (or sacrocaudal region) features a vestigial pelvis and small chevron bones.[14] The flippers have four digits. The lungs and heart are relatively small which suggests that the pygmy right is not a deep diver. The larynx is reported to be different from any other cetacean.[4] Like other mysticetes, the pygmy right has a large laryngeal sac, but in contrast to other mysticetes, this sac is positioned on the right side of the midline in the pygmy right. The presence of this laryngeal sac can possibly be the explanation for the long thorax and flattened ribs, but the peculiar ribs have been the source many speculations.[13]

Analysis of the stomach contents of dead pygmy right whales indicates that it feeds on copepods and euphausiids. The social and mating structures are unknown. The whale is typically seen alone or in pairs, sometimes associated with other cetaceans (including dolphins, pilot whales, minke whales, and once a sei whale cow and calf).[4][10][15] Occasionally larger groups are seen — in 2001 a group of 14 were seen at 46°S in the South Pacific about 450 km southeast of New Zealand, while in 1992 a group of about 80 individuals were seen 320 nm southwest of Cape Leeuwin[2] and another group of over 100 individuals were sighted in June 2007 about 40 km southwest of Portland, Victoria.[16][17]

Population and distribution

The pygmy right whale is among the least studied cetaceans (as of 2008 fewer than 25 "at sea" sightings of the species have been made).[4] The species lives in the Southern Hemisphere and is believed to be circumpolar, living in a band from about 30°S to 55°S[2] in areas with surface water temperature between 5 and 20 °C (41 and 68 °F).[15] Individuals have been found on the coasts of Chile,[18] Tierra del Fuego, Namibia, South Africa, Australia and New Zealand. One group may be a year-round resident off Tasmania.[15] The total population is unknown.

Whaling and whale-watching

On account of its relatively small size and sparse distribution the pygmy right whale has rarely been taken by whalers. A 3.39 metres (11.1 ft) male was taken off South Africa in 1917,[19] and it is likely that a few pygmy rights were taken opportunistically by whalers hunting minke whales. Also a few pygmy right whales are known to have been caught in fishing nets. However these factors are not believed to have had a significant impact on the population.

Most data about pygmy right whales come from individual specimens washed up on coastlines; they are rarely encountered at sea and so they are not the primary subject of any whale watching cruises.

Conservation

The pygmy right whale is listed on Appendix II [20] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix II [20] as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.

The pygmy right whale is also covered by Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region (Pacific Cetaceans MOU).[21]

References

  1. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  2. ↑ 2.0 2.1 2.2 Lua error in package.lua at line 80: module 'strict' not found.
  3. ↑ 3.0 3.1 Lua error in package.lua at line 80: module 'strict' not found.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 4.7 Lua error in package.lua at line 80: module 'strict' not found.
  5. ↑ Cousteau, Jacques, Whales (1986), p. 70.
  6. ↑ Reeves, Randall, Guide to Marine Mammals of the World (2002), p. 202.
  7. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  8. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  9. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  10. ↑ 10.0 10.1 Lua error in package.lua at line 80: module 'strict' not found.
  11. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  12. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  13. ↑ 13.0 13.1 Lua error in package.lua at line 80: module 'strict' not found.
  14. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  15. ↑ 15.0 15.1 15.2 Lua error in package.lua at line 80: module 'strict' not found.
  16. ↑ Lua error in package.lua at line 80: module 'strict' not found.
  17. ↑ Gill, P. C., Kemper, C. M., Talbot, M. & Lydon, S. A. 2008. "Large group of pygmy right whales seen in a shelf upwelling region off Victoria, Australia". Marine Mammal Science 24, 962-968.
  18. ↑ Cabrera, E., Carlson, C., Galletti V.M., B., Cardenas, J.C. and Brownell Jr., R.L. 2005. A pygmy right whale (Caperea marginata) from Chiloe Island, Chile. SC/57/O20.
  19. ↑ Best, P. B., & Ross, G. J. (1986). "Catches of right whales from shore-based establishments in southern Africa, 1792-1975". Reports of the International Whaling Commission, 10, 275-289.
  20. ↑ 20.0 20.1 "Appendix II" of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005 and 2008. Effective: 5 March 2009.
  21. ↑ Lua error in package.lua at line 80: module 'strict' not found.
General references

External links

  • Lua error in package.lua at line 80: module 'strict' not found. Dissection of a stranded pygmy right whale.
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