Ziphiidae: Wikis

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Beaked whales
Fossil range: Miocene–Recent
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Sowerby's Beaked Whale (on Faroese stamp)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Subclass: Theria
Infraclass: Eutheria
Order: Cetacea
Suborder: Odontoceti
Family: Ziphiidae
Gray, 1850
Genera

Berardius
Hyperoodon
Indopacetus
Mesoplodon
Tasmacetus
Ziphius

Beaked whales are creatures of the ocean deeps, feeding 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 (1,038 fathoms) and possibly more.[1] They are currently the only marine mammals whose evolution is believed to have been shaped by a secondary sexual characteristic (the male's teeth).

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.

Contents

Physical characteristics

Beaked whales are moderate in size, ranging from 4 to 13 metres (13 to 43 ft) and weighing from 1 to 15 tonnes (0.98 to 15 LT; 1.1 to 17 ST). Their key distinguishing feature is the presence of a 'beak', somewhat similar to 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 females. Beaked whale species are often sexually dimorphic—one or the other sex is significantly larger. The adult males often possess a dramatically bulging forehead.[2]

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, color, forehead shape and beak length.

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Teeth

In December 2008, researchers from the Marine Mammal Institute at Oregon State University completed a DNA tree of all 21 known species of beaked whale. Among the results of this study was the conclusion that the male's teeth are actually a secondary sexual characteristic, similar to the antlers of male deer. Each species' teeth has a characteristically unique shape. Females observe the teeth to help select mates, because the different species are otherwise quite similar in appearance.

The teeth also play an important role in competing to control a harem. This is believed to be the first known instance of a secondary sexual characteristic having shaped the evolution of a marine mammal.[3]

Taxonomy

Beaked whales comprise at least twenty species of small whale in the family Ziphiidae, which is one of the least-known families of large mammals: several species have been described only in the last two decades, and others may remain undiscovered. Six genera have been identified. Three of these, Indopacetus, the Hyperoodon and the Mesoplodon, are united in a single subfamily, the Hyperoodontinae.

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.

Extinct relatives

As many as ten genera predates humans. Some included ancestors of giant beaked whales (Berardius), such as Microberardius. The Cuvier's beaked whale (Ziphius) had many relatives, such as Caviziphius, Archaeoziphius, and Izikoziphius. They were probably preyed upon by predatory whales and sharks, including Carcharocles megalodon.

Ecology

Feeding

Beaked whales' feeding mechanism, suction feeding, is unique. Instead of catching prey with teeth, they suck it into their oral cavity. Their tongue can move very freely, and when suddenly retracted at the same time as the gular (throat) floor is distended, the pressure immediately drops within their mouth and the prey is sucked in with the water.[4]

Diet is primarily deep water squid, but also fish and some crustaceans.

Range and habitat

Beaked whales are found in all oceans and most species rarely venture into the relatively shallow water of the continental shelves.

Known areas where they congregate include the deep waters off the edge of continental shelves, and bottom features like seamounts, canyons, escarpments, and oceanic islands including the Azores and the Canaries.

Their range varies by species.

Life history

Beaked whales have been observed living in "harem-like" groups, where several females and young are accompanied by a single male. Beaked whales tend to associate in small family groups.

Conservation status

For many years, most 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 predator they are, like raptors, particularly vulnerable to build-up of biocontaminants. They frequently ingest plastic bags (which do not break down and can be lethal).
  • They more and more frequently become trapped in trawl nets, due to the expansion of deepwater fisheries (particularly since the collapse of Atlantic Cod stocks late in the 20th century)
  • They are assumed to be vulnerable to prey depletion.
  • Beaked whales are especially vulnerable to modern ultra-loud sonar, which may force them to surface too quickly and die from the bends.[5]

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 because their status is unknown.

References

  1. ^ Lewis Smith (October 17, 2006). "It's official: New free-diving record is 1,899 meters (6,230 ft)". CDNN. http://www.cdnn.info/news/industry/i061017a.html.  
  2. ^ Christensen, Ivar (1984). Macdonald, D.. ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 210–211. ISBN 0-87196-871-1.  
  3. ^ "Whale's teeth are aid to mating". BBC. December 2008. http://news.bbc.co.uk/2/hi/science/nature/7783517.stm.  
  4. ^ "Suction feeding in beaked whales: Morphological and experimental evidence". Natural History Museum of Los Angeles County. 1996. http://www.nhm.org/research/mammals/suction.htm.  
  5. ^ Navy sonar blamed for death of beaked whales found washed up in the Hebrides - The Independent

External links


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

Contents

Translingual

Etymology

Proper noun

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Wikipedia has an article on:

Wikipedia

Ziphiidae

  1. a taxonomic family, within suborder Odontoceti - the beaked whales
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Wikispecies has information on:

Wikispecies

See also

  • Archaeoziphius
  • Berardius
  • Caviziphius
  • Hyperoodon
  • Indopacetus
  • Mesoplodon
  • Tasmacetus
  • Ziphius

Wikispecies

Up to date as of January 23, 2010

From Wikispecies

Taxonavigation

Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Mammalia
Subclassis: Theria
Infraclassis: Placentalia
Superordo: Cetartiodactyla
Ordo: Cetacea
Subordo: Odontoceti
Infraordines: Physeterida
Superfamiliae: Ziphioidea
Familia: Ziphiidae
Subfamiliae: Berardiinae - Hyperoodontinae - Ziphiinae - incertae sedis

Name

Ziphiidae Gray, 1850

References

  • Ziphiidae on Mammal species of the World.
    Don E. Wilson & DeeAnn M. Reeder (editors). 2005. Mammal Species of the World. A Taxonomic and Geographic Reference (3rd ed).
  • Mammal Species of the World, A Taxonomic and Geographic Reference, 3rd edition, 2005 ISBN 0801882214

Vernacular names

English: Beaked whale
日本語: アカボウクジラ科
Türkçe: Gagalı balinagiller
中文: 劍吻鯨科

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