Beaked whale

Taxobox
name = Beaked whales
fossil_range = Miocene - Recent

---

image_width = 250px
image_caption = Sowerby's Beaked Whale (on Faroese stamp)
regnum = Animalia
phylum = Chordata
classis = Mammalia
subclassis = Theria
infraclassis = Eutheria
ordo = Cetacea
subordo = Odontoceti
familia = Ziphiidae
familia_authority = Gray, 1850
subdivision_ranks = Genera
subdivision = "Berardius"
"Hyperoodon"
"Indopacetus"
"Mesoplodon"
"Tasmacetus"
"Ziphius"A beaked whale is any of at least twenty species of small whale in the family Ziphiidae. They are one of the least-known families of large mammals: several species have only been described in the last two decades, and it is entirely possible that more remain as yet undiscovered. Six genera have been identified. Three of these, "Indopacetus", the "Hyperoodon" and the "Mesoplodon", are united in a single subfamily, the Hyperoodontinae.

Beaked whales are creatures of the ocean deeps, feeding, so far as is known, on or near the sea floor. They have an extraordinary ability to dive for long periods—20 to 30 minutes is common, and 85 minute dives have been recorded—and to great depths: 1,899 metres and possibly more. [cite news|url=http://www.cdnn.info/news/industry/i061017a.html|title=It's official: New free-diving record is 1,899 meters (6,230 ft)|date=October 17, 2006|publisher=CDNN|author=Lewis Smith]

Physical characteristics

Beaked whales are moderately large in size, ranging from 4 to 13 metres in length, and weighing from 1 to 15 tonnes. Their key distinguishing feature is the presence of a 'beak', somewhat similar to that of many dolphins. Other distinctive features include a pair of converging grooves under the throat, and the absence of a notch in the tail fluke. Although Shepherd's Beaked Whale is an exception, most species have only one or two pairs of teeth, and even these do not erupt in the females. Beaked whale species are often sexually dimorphic, with one or the other sex being significantly larger, and the adult males often possessing a dramatically bulging forehead.cite book |editor=Macdonald, D.|author= Christensen, Ivar|year=1984 |title= The Encyclopedia of Mammals|publisher= Facts on File|location=New York|pages= 210-211|isbn= 0-87196-871-1]

Classification

The beaked whales are the second-largest family of Cetaceans (after the dolphins) and were one of the first groups to diverge from the ancestral lineage. The earliest known beaked whale fossils date to the Miocene, about 20 million years ago.

* ORDER CETACEA
* Suborder Odontoceti: toothed whales
** Family Kogiidae: Pygmy and Dwarf Sperm Whales
** Family Ziphiidae
*** Genus "Berardius"
**** Arnoux's Beaked Whale, "Berardius arnuxii"
**** Baird's Beaked Whale, "Berardius bairdii"
*** Genus "Hyperoodon": Bottlenose whales
**** Northern Bottlenose Whale, "Hyperoodon ampullatus"
**** Southern Bottlenose Whale, "Hyperoodon planifrons"
*** Genus "Indopacetus"
**** Longman's Beaked Whale, "Indopacetus pacificus"
*** Genus "Mesoplodon"
**** Sowerby's Beaked Whale, "Mesoplodon bidens"
**** Andrews' Beaked Whale, "Mesoplodon bowdoini"
**** Hubbs' Beaked Whale, "Mesoplodon carlhubbsi"
**** Blainville's Beaked Whale, "Mesoplodon densirostris"
**** Gervais' Beaked Whale, "Mesoplodon europaeus"
**** Ginkgo-toothed Beaked Whale, "Mesoplodon ginkgodens"
**** Gray's Beaked Whale, "Mesoplodon grayi"
**** Hector's Beaked Whale, "Mesoplodon hectori"
**** Strap-toothed Whale, "Mesoplodon layardii"
**** True's Beaked Whale, "Mesoplodon mirus"
**** Pygmy Beaked Whale, "Mesoplodon peruvianus"
**** Perrin's Beaked Whale, "Mesoplodon perrini"
**** Stejneger's Beaked Whale, "Mesoplodon stejnegeri"
**** Spade Toothed Whale, "Mesoplodon traversii"
*** Genus "Tasmacetus"
**** Shepherd's Beaked Whale, "Tasmacetus sheperdi"
*** Genus "Ziphius"
**** Cuvier's Beaked Whale, "Ziphius cavirostris"

Ecology

Beaked whales possess a unique feeding mechanism known as suction feeding. Instead of catching their prey with teeth, it is sucked into their oral cavity. Their tongue can move very freely, and when suddenly retracted at the same time as the gular floor is distended, the pressure immediately drops within their mouth and the prey is sucked in with the water. [cite web|url=http://www.nhm.org/research/mammals/suction.htm|title=Suction feeding in beaked whales: Morphological and experimental evidence|publisher=Natural History Museum of Los Angeles County|date=1996] Beaked whales are found in all oceans and most species rarely venture into the relatively shallow water of the continental shelves. They are very difficult to identify in the wild: body form varies little from one species to another, and the observer must rely on often subtle differences in size, colour, shape of forehead, and length of beak.

Beaked whales tend to associate in small family groups and avoid shallow water. Known areas where they congregate include the deep waters off the edge of continental shelves, and close to bottom features like seamounts, canyons, escarpments, and oceanic islands including the Azores and the Canaries. Diet is primarily deep water squid, but also fish and some crustaceans.

Because of their preferred habitat and their inclination to make long dives, they are very difficult to observe, and little is known of most species. Several have yet to be formally described or named; others are known only from remains and have never been sighted alive. Only three or four of the 20-odd species are reasonably well-known. Baird's and Cuvier's Beaked Whales were subject to commercial exploitation off the coast of Japan; and the Northern Bottlenose Whale was extensively hunted in the northern part of the North Atlantic late in the 19th and early in the 20th centuries.

Conservation status

For many years, most of the beaked whale species were insulated from human impact because of their remote habitat. However there are now clear issues of concern: studies of stranded beaked whales show rising levels of toxic chemicals in their blubber (as a top-order predator they are, like raptors, particularly vulnerable to build-up of biocontaminants) and they frequently have ingested plastic bags (which do not break down and can be lethal). With the ongoing worldwide expansion of deepwater fisheries (particularly since the collapse of Atlantic Cod stocks late in the 20th century), beaked whales are more and more frequently trapped in trawl nets, and are also assumed to be vulnerable to prey depletion.

Beaked whales are proving especially vulnerable to modern ultra-loud, submarine seeking, sonars which may force them to surface too quickly, and die from the bends. [ [http://www.independent.co.uk/environment/nature/navy-sonar-blamed-for-death-of-beaked-whales-found-washed-up-in-the-hebrides-805399.html Navy sonar blamed for death of beaked whales found washed up in the Hebrides] - "The Independent"]

Four of the more than 20 beaked whale species are classified by the IUCN as "lower risk, conservation dependent": Arnoux's and Baird's Beaked Whales, and the Northern and Southern Bottlenose Whales. None of the remaining species are classified - not because they are considered secure, but because their status is simply unknown.

References

External links

* [http://news.bbc.co.uk/1/hi/sci/tech/7641537.stm Beaked whales - into the abyss] - BBC News article