Mesoplodont whale
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The mesoplodont whales are the fourteen species of whale that make up the genus Mesoplodon, making it the single largest genus in the cetacean order. Two species were discovered for the first time as recently as 1991 and 1995, and many marine biologists expect to discover more species in the future. This genus is traditionally characterized by the size and shape of the skull, in particular the distinctive curved beak shape at the jaw, shaped rather like a playground slide. Some other whale species share this property, and together they are known as the beaked whales. The word mesoplodon comes from the Greek meso- (middle) - hopla (arms) - odon (teeth), and may be translated as 'armed with a tooth in the centre of the jaw'.
Species
English name (most common first), Latin name, known distribution:
- Sowerby's Beaked Whale M. bidens
- Andrews' Beaked Whale M. bowdoini
- Hubbs' Beaked Whale M. carlhubbsi
- Blainville's Beaked Whale M. densirostris
- Gervais' Beaked Whale M. europaeus
- Ginkgo-toothed Beaked Whale M. ginkgodens
- Gray's Beaked Whale M. grayi
- Hector's Beaked Whale M. hectori
- Layard's Beaked Whale M. layardii
- True's Beaked Whale M. mirus
- Perrin's Beaked Whale, M. perrini, eastern Pacific. First reported in 1997 from four sightings off the coast of California. Formally identified as a separate species by Dalebout et al in 2002. Previously the individuals had been thought to have been Hector's Beaked Whale.
- Pygmy Beaked Whale, Peruvian Beaked Whale, Lesser Beaked Whale, M. peruvianus, off west coast of South America
- Stejneger's Beaked Whale, Bering Sea Beaked Whale, M. stejnegeri, Cool to sub-Arctic Pacific Ocean, Bering Sea
- Spade-toothed Beaked Whale, M. traversii, tropical Eastern Pacific and New Zealand
Longman's Beaked Whale (also known as the Indo-Pacific Beaked Whale) is also sometimes classed in the Mesoplodon genus. However, most authorities follow the lead of Joesph Curtis Moore who in the 1960s put it in its own genus - the Indopacetus.
Physical description and behaviour
Physical data is scant for almost all species on account of the fact that mesoplodons live far out to sea. For instance, it is not known whether females are larger than males. From beached individuals we know that the whales are small, ranged from 4-6m in length and are typically about 1000-1500kg in weight.
Species typically have a small triangular dorsal fin about two-thirds to three-quarters along the back.
Virtually nothing is known about mesoplodon behaviour as so few have been seen alive. Further, their range of behaviours at the surface appears limited to slow swimming. There is usually no surface blow and there have been no reports of a mesoplodon fluking (raising their tail fluke clear of the water on diving).
Longeveity, lactation and gestation data is non-existent.
Conservation
The mesoplodon species populations are unknown and consequently the species are generally omitted from Red Data Species lists. The main threat from humans is the accidental capture in drift nets.
