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Beaked whales (
systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivial ...
Ziphiidae) are a
family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...
of
cetaceans Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel th ...
noted as being one of the least known groups of mammals because of their deep-sea habitat and apparent low abundance. Only three or four of the 24 species are reasonably well-known. Baird's beaked whales and
Cuvier's beaked whale The Cuvier's beaked whale, goose-beaked whale, or ziphius (''Ziphius cavirostris'') is the most widely distributed of all beaked whales in the family Ziphiidae. It is smaller than most baleen whales yet large among beaked whales. Cuvier's beaked ...
s were subject to commercial exploitation, off the coast of
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
, while the northern bottlenose whale was extensively hunted in the northern part of the
North Atlantic The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe a ...
late in the 19th and early 20th centuries. Reports emerged in late 2020 of the possible discovery of a new beaked whale species off the coast of
Mexico Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
, the taxonomy of which had not been determined .


Physical characteristics

Beaked whales are moderate in size, ranging from and weighing from . Their key distinguishing feature is the presence of a 'beak', somewhat similar to many
dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the b ...
s. 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 Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most ani ...
one or the other sex is significantly larger. The adult males often possess a large bulging forehead, some to an extreme feature. However, aside from dentition and size, very few morphological differences exist between male and female beaked whales. Individual species are very difficult to identify in the wild, since body form varies little from one species to another. The observer must rely on often subtle differences in size, color, forehead shape, and beak length. In the skull, the expansion of the premaxillary process can be a key feature to indentification. The blubber of these whales is almost entirely (94%) composed of wax ester, a unique characteristic of this family.


Dentition

Beaked whales are unique among toothed whales in that most species only have one pair of teeth. The teeth are tusk-like, but are only visible in males, which are presumed to use these teeth in combat for females for reproductive rights. In females, the teeth do not develop and remain hidden in the gum tissues. In December 2008, researchers from the Marine Mammal Institute at
Oregon State University Oregon State University (OSU) is a public land-grant, research university in Corvallis, Oregon. OSU offers more than 200 undergraduate-degree programs along with a variety of graduate and doctoral degrees. It has the 10th largest engineering ...
completed a DNA tree of 13 of 15 known species of '' Mesoplodon'' beaked whales (excluding the spade-toothed whale, which was then only known from a skeletal specimen and a few stranded specimens). Among the results of this study was the conclusion that the male's teeth are actually a secondary sexual characteristic, similar to the
antler Antlers are extensions of an animal's skull found in members of the Cervidae (deer) family. Antlers are a single structure composed of bone, cartilage, fibrous tissue, skin, nerves, and blood vessels. They are generally found only on ...
s of male
deer Deer or true deer are hoofed ruminant mammals forming the family Cervidae. The two main groups of deer are the Cervinae, including the muntjac, the elk (wapiti), the red deer, and the fallow deer; and the Capreolinae, including the re ...
. Each species' teeth have a characteristically unique shape. In some cases, these teeth even hinder feeding; in the strap-toothed whale, for example, the teeth curve over the upper jaw, effectively limiting the gape to a few centimeters. Females are presumed to select mates based on the shape of the teeth, because the different species are otherwise quite similar in appearance. The social structure is not well known, but sightings of single males accompanying multiple females suggest a
polygynous Polygyny (; from Neoclassical Greek πολυγυνία (); ) is the most common and accepted form of polygamy around the world, entailing the marriage of a man with several women. Incidence Polygyny is more widespread in Africa than in any ...
mating system, which would considerably limit the number of males a female can choose.


Taxonomy

Beaked whales comprise at least 22 species. Several species have been described only in the last two decades. Six
genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
have been identified. The beaked whales are the second-largest family of
cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel th ...
ns (after the
dolphin A dolphin is an aquatic mammal within the infraorder Cetacea. Dolphin species belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontoporiidae (the b ...
s). They were one of the first groups to diverge from the ancestral lineage. The earliest known beaked whale
fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...
s date to the
Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recen ...
, about 15 million years ago. * Order
Cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often large size and exclusively carnivorous diet. They propel th ...
* Suborder
Odontoceti The toothed whales (also called odontocetes, systematic name Odontoceti) are a parvorder of cetaceans that includes dolphins, porpoises, and all other whales possessing teeth, such as the beaked whales and sperm whales. Seventy-three species ...
: toothed whales ** Family Ziphiidae *** ''
Incertae sedis ' () or ''problematica'' is a term used for a taxonomic group where its broader relationships are unknown or undefined. Alternatively, such groups are frequently referred to as "enigmatic taxa". In the system of open nomenclature, uncertain ...
'' **** Genus †'' Anoplonassa'' **** Genus †'' Caviziphius'' **** Genus †'' Cetorhynchus'' **** Genus †'' Eboroziphius'' **** Genus †'' Pelycorhamphus'' *** Basal forms **** Genus †'' Aporotus'' **** Genus †''
Beneziphius ''Beneziphius'' is an extinct genus of ziphiid cetacean known from late Miocene to Pliocene marine deposits in Belgium and fishing grounds off Spain. The genus name honors Pierre-Joseph van Beneden Pierre-Joseph van Beneden FRS FRSE FGS FZS (1 ...
'' **** Genus †'' Chavinziphius'' **** Genus †'' Chimuziphius'' **** Genus †'' Choneziphius'' **** Genus †'' Dagonodum'' **** Genus †''
Globicetus ''Globicetus'' is an extinct genus of ziphiidae cetaceans, with one species, ''G. hiberus'', from the Miocene of Portugal and Spain.Bianucci G., Miján I, Lambert O., Post K. & Mateus O. 2013. Bizarre fossil beaked whales (Odontoceti, Ziphiidae) ...
'' **** Genus †'' Imocetus'' **** Genus †''
Messapicetus ''Messapicetus'' is an extinct genus of beaked whale from the Late Miocene. It currently holds two species, ''M. longirostris'' from the Tortonian of Italy and ''M. gregarius'' from the Pisco Formation of Peru. However, a third unnamed species is ...
'' **** Genus †'' Ninoziphius'' **** Genus †'' Notoziphius'' **** Genus †''
Tusciziphius ''Tusciziphius'' is an extinct genus of ziphiid cetaceans. The distribution includes the Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist C ...
'' **** Genus †'' Ziphirostrum'' *** Subfamily Berardiinae **** Genus †'' Archaeoziphius'' **** Genus ''
Berardius The four-toothed whales or giant beaked whales are beaked whales in the genus ''Berardius''. They include Arnoux's beaked whale (''Berardius arnuxii'') in cold Southern Hemispheric waters, and Baird's beaked whale (''Berardius bairdii'') in th ...
'' ***** ''B. arnuxii'',
Arnoux's beaked whale Arnoux's beaked whale (''Berardius arnuxii''), also called the southern four-toothed whale, southern beaked whale, New Zealand beaked whale, southern giant bottlenose whale and southern porpoise whale is one of the species of '' Berardius''. Arno ...
***** ''B. bairdii'', Baird's beaked whale ***** ''Berardius minimus'',
Sato's beaked whale Sato's beaked whale (''Berardius minimus'') is a little-known species of four-toothed whale. Description Sato's beaked whale is one of the poorly distinguished species in the genus ''Berardius''. It was distinguished from Arnoux's and Baird's ...
***** †'' B. kobayashii'' **** Genus †'' Microberardius'' *** Subfamily Hyperoodontinae **** Genus †''
Africanacetus ''Africanacetus'' is an extinct genus of ziphiid cetacea Cetacea (; , ) is an infraorder of aquatic mammals that includes whales, dolphins, and porpoises. Key characteristics are their fully aquatic lifestyle, streamlined body shape, often ...
'' **** Genus †'' Belemnoziphius'' **** Genus ''Hyperoodon'',
bottlenose whale ''Hyperoodon'' (or ''Hyperoödon'') is a genus of beaked whale, containing just two species: the Northern and Southern bottlenose whales. While not in the genus ''Hyperoodon'', Longman's beaked whale The tropical bottlenose whale (''Indopac ...
s ***** ''H. ampullatus'', northern bottlenose whale ***** ''H. planifrons'',
southern bottlenose whale The southern bottlenose whale (''Hyperoodon planifrons'') is a species of whale, in the Ziphiid family, one of two members of the genus ''Hyperoodon''. Seldom observed, the southern bottlenose whale is resident in Antarctic waters. The species w ...
**** Genus †'' Ihlengesi'' **** Genus '' Indopacetus'' ***** ''I. pacificus'',
tropical bottlenose whale The tropical bottlenose whale (''Indopacetus pacificus''), also known as the Indo-Pacific beaked whale or Longman's beaked whale, was considered to be the world's rarest cetacean until recently, but the spade-toothed whale now holds that position ...
**** Genus †'' Khoikhoicetus'' **** Genus '' Mesoplodon'', mesoplodont whales ***** ''M. bidens'', Sowerby's beaked whale ***** ''M. bowdoini'', Andrews' beaked whale ***** ''M. carlhubbsi'', Hubbs' beaked whale ***** ''M. densirostris'',
Blainville's beaked whale Blainville's beaked whale (''Mesoplodon densirostris''), or the dense-beaked whale, is believed to be the widest ranging mesoplodont whale. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw � ...
***** ''M. eueu'', Ramari's beaked whale *****''M. europaeus'', Gervais's beaked whale ***** ''M. ginkgodens'',
ginkgo-toothed beaked whale The ginkgo-toothed beaked whale (''Mesoplodon ginkgodens'') is a poorly known species of whale even for a beaked whale, and was named for the unusual shape of its dual teeth. It is a fairly typical-looking species, but is notable for the males ...
***** ''M. grayi'',
Gray's beaked whale Gray's beaked whale (''Mesoplodon grayi''), sometimes known as Haast's beaked whale, the scamperdown whale, or the southern beaked whale, is one of the better-known members of the genus ''Mesoplodon''. This species is fairly gregarious and strand ...
***** ''M. hectori'', Hector's beaked whale ***** ''M. layardii'', strap-toothed whale ***** ''M. mirus'', True's beaked whale ***** ''M. peruvianus'', pygmy beaked whale ***** ''M. perrini'', Perrin's beaked whale ***** ''M. stejnegeri'', Stejneger's beaked whale ***** ''M. traversii'', spade-toothed whale ***** ''M. hotaula'',
Deraniyagala's beaked whale Deraniyagala's beaked whale (''Mesoplodon hotaula'') is a species of mesoplodont whale. Taxonomy Deraniyagala's beaked whale was once synonymous with the Ginkgo-toothed beaked whale (''Mesoplodon ginkgodens''), until several studies confirmed ...
**** Genus †''
Nenga ''Nenga'' is a monoecious genus of flowering plant in the palm family. It is native to Southeast Asia and commonly called pinang palm. ''N. gajah'' is the aberration in the genus with its short internodes, marcescent leaves and interfoliar i ...
'' **** Genus †'' Pterocetus'' **** Genus †'' Xhosacetus'' *** Subfamily Ziphiinae **** Genus †'' Caviziphius'' **** Genus †'' Izikoziphius'' **** Genus †'' Nazcacetus'' **** Genus '' Tasmacetus'' ***** ''T. shepherdi'', Shepherd's beaked whale **** Genus '' Ziphius'' ***** ''Z. cavirostris'',
Cuvier's beaked whale The Cuvier's beaked whale, goose-beaked whale, or ziphius (''Ziphius cavirostris'') is the most widely distributed of all beaked whales in the family Ziphiidae. It is smaller than most baleen whales yet large among beaked whales. Cuvier's beaked ...


Evolutionary history

As many as 26 genera antedate humans. These include ancestors of giant beaked whales (''
Berardius The four-toothed whales or giant beaked whales are beaked whales in the genus ''Berardius''. They include Arnoux's beaked whale (''Berardius arnuxii'') in cold Southern Hemispheric waters, and Baird's beaked whale (''Berardius bairdii'') in th ...
''), such as '' Microberardius'', and ancestors of Cuvier's beaked whale ('' Ziphius''); they had many relatives, such as '' Caviziphius'', '' Archaeoziphius'', and '' Izikoziphius''. They were probably preyed upon by predatory whales and
shark Sharks are a group of elasmobranch fish characterized by a cartilaginous skeleton, five to seven gill slits on the sides of the head, and pectoral fins that are not fused to the head. Modern sharks are classified within the clade Selachi ...
s, including '' Otodus megalodon''. Recently, a large fossil ziphiid sample was discovered off the South African coast, confirming the extant ziphiid diversity might just be a remnant of a higher past diversity. After studying numerous fossil skulls off the shore of Iberia and South Africa, researchers discovered the absence of functional maxillary teeth in all South African fossil ziphiids, which is evidence that suction feeding had already developed in several beaked whale lineages during the Miocene. Researchers also found fossil ziphiids with robust skulls, signaling that tusks were used for male-male interactions (speculated with extant beaked whales).


Ecology


Diving

Beaked whales are deep divers with extreme dive profiles. They regularly dive deeper than to echolocate for food, and these deep dives are often followed by multiple shallower dives less than 500 m. This pattern is not always followed, however. Animals have been observed spending more than an hour at or near the surface breathing. Beaked whales are often seen surfacing synchronously, but asynchronous surfacing has also been observed. In March 2014, a study by Cascadia Research revealed that Cuvier's beaked whales were recorded to dive at least 2992 m in depth, a mammalian record. Another study, published in 2020, reported a Cuvier's beaked whale making a dive that lasted 222 minutes, another mammalian record. Deep-diving mammals face a number of challenges related to extended breath-holding and hydrostatic pressure. Cetaceans and pinnipeds that prolong
apnea Apnea, BrE: apnoea, is the temporal cessation of breathing. During apnea, there is no movement of the muscles of inhalation, and the volume of the lungs initially remains unchanged. Depending on how blocked the airways are ( patency), there ma ...
must optimize the size and use of their oxygen stores, and they must deal with the accumulation of
lactic acid Lactic acid is an organic acid. It has a molecular formula . It is white in the solid state and it is miscible with water. When in the dissolved state, it forms a colorless solution. Production includes both artificial synthesis as well as nat ...
due to anaerobic metabolism. Beaked whales have several anatomical adaptations to deep diving: large
spleen The spleen is an organ found in almost all vertebrates. Similar in structure to a large lymph node, it acts primarily as a blood filter. The word spleen comes .
s, livers, and body shape. Most cetaceans have small spleens. However, beaked whales have much larger spleens than delphinids, and may have larger livers, as well. These anatomical traits, which are important for filtering blood, could be adaptations to deep diving. Another notable anatomical adaptation among beaked whales is a slight depression in the body wall that allows them to hold their pectoral flippers tightly against their bodies for increased streamlining. However, they are not invulnerable to the effects of diving so deep and so often. Cascadia Research shows that the deeper the whales dive, the less often they dive per day, cutting their efforts by at least 40%. The challenges of deep diving are also overcome by the unique diving physiology of beaked whales. Oxygen storage during dives is mostly achieved by blood hemoglobin and muscle myoglobin. While the whale is diving, its heart rate slows and blood flow changes. This physiological dive response ensures oxygen-sensitive tissues maintain a supply of oxygen, while those tissues tolerant to hypoxia receive less blood flow. Additionally, lung collapse obviates the exchange of lung gas with blood, likely minimizing the uptake of nitrogen by tissues.


Feeding

The throats of all beaked whales have a bilaterally paired set of grooves that are associated with their unique feeding mechanism, suction feeding. Instead of capturing prey with their teeth, beaked whales suck it into their oral cavity. Suction is aided by the throat grooves, which stretch and expand to accommodate food. Their tongues can move very freely. By suddenly retracting the tongue and distending the gular (throat) floor, pressure immediately drops within the mouth, sucking the prey in with the water. Dietary information is available from stomach contents analyses of stranded beaked whales and from whaling operations. Their preferred diet is primarily deep-water squid, but also benthic and benthopelagic fish and some crustaceans, mostly taken near the sea floor. In a recent study, gouge marks in the sea floor were interpreted to be a result of feeding activities by beaked whales. To understand the hunting and foraging behavior of beaked whales, researchers used sound and orientation recording devices on two species:
Cuvier's beaked whale The Cuvier's beaked whale, goose-beaked whale, or ziphius (''Ziphius cavirostris'') is the most widely distributed of all beaked whales in the family Ziphiidae. It is smaller than most baleen whales yet large among beaked whales. Cuvier's beaked ...
(''Ziphius cavirostris'') and
Blainville's beaked whale Blainville's beaked whale (''Mesoplodon densirostris''), or the dense-beaked whale, is believed to be the widest ranging mesoplodont whale. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw � ...
(''Mesoplodon densirostris''). These whales hunt by echolocation in deep water (where the majority of their prey is located) between about and usually catch about 30 prey per dive. Cuvier's beaked whales must forage on average at for 58 minutes and Blainville's beaked whales typically forage at deep for an average of 47 minutes.


Range and habitat

The family Ziphiidae is one of the most widespread families of cetaceans, ranging from the ice edges at both the north and south poles, to the equator in all the oceans. Specific ranges vary greatly by species, though beaked whales typically inhabit offshore waters that are at least 300 m deep. Beaked whales are known to congregate in deep waters off the edge of continental shelves, and bottom features, such as
seamounts A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...
,
canyons A canyon (from ; archaic British English spelling: ''cañon''), or gorge, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency to cu ...
,
escarpments An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. The terms ''scarp'' and ''scarp face'' are often used interchangeably with ''esca ...
, and oceanic islands, including the
Azores ) , motto =( en, "Rather die free than subjected in peace") , anthem= ( en, "Anthem of the Azores") , image_map=Locator_map_of_Azores_in_EU.svg , map_alt=Location of the Azores within the European Union , map_caption=Location of the Azores wi ...
and the
Canary Islands The Canary Islands (; es, :es:Canarias, Canarias, ), also known informally as the Canaries, are a Spanish Autonomous communities of Spain, autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to ...
, and even off the coasts of Hawaii.


Life history

Very little is known about the life history of beaked whales. The oldest recorded age is 84 years for a male Baird's beaked whale and 54 years for a female. For all other beaked whale species studied, the oldest recorded age is between 27 and 39 years. Sexual maturity is reached between seven and 15 years of age in Baird's beaked whales and northern bottlenose whales. Gestation varies greatly between species, lasting 17 months for Baird's beaked whales and 12 months for the northern bottlenose whale. No data are available on their reproductive rates. Determining group size for beaked whales is difficult, due to their inconspicuous surfacing behavior. Groups of beaked whales, defined as all individuals found in the same location at the same time, have been reported as ranging from one to 100 individuals. Nevertheless, some populations' group size has been estimated from repeated observations. For example, northern and southern bottlenose whales (''H. ampullatus'' and ''H. planifrons''), Cuvier's beaked whales, and Blainville's beaked whales (''Mesoplodon densirostris'') have a reported maximum group size of 20 individuals, with the average ranging from 2.5 to 3.5 individuals. ''Berardius'' species and Longman's beaked whales (''Indopacetus pacificus'') are found in larger groups of up to 100 individuals. Not much information is available about group composition of beaked whales. Only three species have been studied in any detail: northern bottlenose whales, Blainville's beaked whales, and Baird's beaked whales. Female northern bottlenose whales appear to form a loose network of social partners with no obvious long-term associations. In contrast to females, some male northern bottlenose whales have been repeatedly recorded together over several years, and possibly form long-term associations. Studies of Blainville's beaked whales have revealed groups usually consist of a number of females, calves, and/or juvenile animals. These whales are assumed to live in "harem-like" groups, where several females and young are accompanied by a single male. Baird's beaked whales are known to occur in multiple male groups, and in large groups consisting of adult animals of both sexes. Arnoux's beaked whales have also been observed to form large pods of up to 47 individuals off the Southern Ocean off the coast of Kemp Land, Antarctica.


Conservation

For many years, most beaked whale species were insulated from anthropogenic impacts because of their remote habitat. However, now several issues of concern include: * Studies of stranded beaked whales show rising levels of toxic chemicals in their
blubber Blubber is a thick layer of vascularized adipose tissue under the skin of all cetaceans, pinnipeds, penguins, and sirenians. Description Lipid-rich, collagen fiber-laced blubber comprises the hypodermis and covers the whole body, except fo ...
. * As a
top predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic ...
, beaked whales, like
raptor Raptor or RAPTOR may refer to: Animals The word "raptor" refers to several groups of bird-like dinosaurs which primarily capture and subdue/kill prey with their talons. * Raptor (bird) or bird of prey, a bird that primarily hunts and feeds on v ...
s, are particularly vulnerable to build-up of biocontaminants. They can ingest plastic (which can be lethal). * They more frequently become trapped in trawl nets, due to the expansion of deepwater fisheries. * Decompression sickness A major conservation concern for beaked whales (family Ziphiidae) is they appear to be vulnerable to modern sonar operations, which arises from recent strandings that temporally and physically coincide with naval sonar exercises. Mid-frequency active sonar (MFAS), developed in the 1950s for submarine detection, is thought to induce panic when experienced by whales at depth. This raises their heart-rates, forcing them to attempt to rapidly ascend toward the surface in search of air. This artificially-induced rapid ascent can cause decompression. ''Post mortem'' examinations of the stranded whales in concurrence with naval exercises have reported the presence of hemorrhaging near the ears or gas and fat emboli, which could have a deleterious impact on beaked whales that is analogous to decompression sickness in humans. Gas and fat emboli have been shown to cause nervous and cardiovascular system dysfunction, respiratory distress, pain, and disorientation in both humans and animals. In the inner ear, gas embolism can cause hemorrhages, leading to disorientation or vestibular dysfunction. Breath-holding divers, like beaked whales, can develop decompression-related problems (the "bends") when they return to the surface after deep dives. This is a possible hypothesis for the mass strandings of pelagic beaked whales associated with sonar-related activities. To illustrate, a diving beaked whale may be surfacing from a deep dive and must pass vertically through varying received sound levels. Since the whale has limited remaining oxygen supplies at the end of a long dive, it probably has limited abilities to display any normal sound avoidance behavior. Instead, the whale must continue to swim toward the surface to replenish its oxygen stores. Avoiding sonar inevitably requires a change in behavior or surfacing pattern. Therefore, sonar in close proximity to groups of beaked whales has the potential to cause hemorrhaging or to disorient the animal, eventually leading to a stranding. Current research reveals two species of beaked whales are most affected by sonar: Cuvier's (''Z. cavirostris'') and Blainville's (''M. densirostris'') beaked whales. These animals have been reported as stranding in correlation with military exercises in Greece, the Bahamas, Madeira, and the Canary Islands. The livers of these animals had the most damage. In 2019, a review of evidence on the mass strandings of beaked whale linked to naval exercises where sonar was used was published. It concluded that the effects of mid-frequency active sonar are strongest on Cuvier's beaked whales but vary among individuals or populations, and the strength of their response may depend on whether the individuals had prior exposure to sonar. The report considered that the most plausible explanation of the symptoms of decompression sickness such as gas embolism found in stranded whales to be the whales' response to sonar. It noted that no more mass strandings had occurred in the Canary Islands once naval exercises where sonar was used were banned there, and recommended that the ban be extended to other areas where mass strandings continue to occur. Four species are classified by the
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
as "lower risk, conservation dependent": Arnoux's and Baird's beaked whales, and the northern and southern
bottlenose whale ''Hyperoodon'' (or ''Hyperoödon'') is a genus of beaked whale, containing just two species: the Northern and Southern bottlenose whales. While not in the genus ''Hyperoodon'', Longman's beaked whale The tropical bottlenose whale (''Indopac ...
s. The status of the remaining species is unknown, preventing classification.


Captivity

Beaked whales live very short lives in captivity when compared to other cetaceans such as common bottlenose dolphins and short-finned pilot whales, most surviving only a few days out of the ocean. The longest time period for a beaked whale living in captivity was 25 days. Alexander and Nicholas, two male beaked whales—their species unknown, though they were thought to be either Hubbs' beaked whale or
Blainville's beaked whale Blainville's beaked whale (''Mesoplodon densirostris''), or the dense-beaked whale, is believed to be the widest ranging mesoplodont whale. The French zoologist Henri de Blainville first described the species in 1817 from a small piece of jaw � ...
—had become stranded in California on 24 August 1989. They were taken to Marine World California. Both of the whales would die of
pneumonia Pneumonia is an inflammatory condition of the lung primarily affecting the small air sacs known as alveoli. Symptoms typically include some combination of productive or dry cough, chest pain, fever, and difficulty breathing. The severit ...
; Nicholas died on 8 September and Alexander died 10 days later. A handful of other beaked whales have been briefly kept in captivity. A juvenile female
Cuvier's beaked whale The Cuvier's beaked whale, goose-beaked whale, or ziphius (''Ziphius cavirostris'') is the most widely distributed of all beaked whales in the family Ziphiidae. It is smaller than most baleen whales yet large among beaked whales. Cuvier's beaked ...
was found stranded on a kelp bed off of Santa Catalina Island on 23 February 1956. She was taken to Marineland of the Pacific, where she was named Martha Washington. On 16 June 1969, a
Cuvier's beaked whale The Cuvier's beaked whale, goose-beaked whale, or ziphius (''Ziphius cavirostris'') is the most widely distributed of all beaked whales in the family Ziphiidae. It is smaller than most baleen whales yet large among beaked whales. Cuvier's beaked ...
live stranded in St. Augustine. The whale, thought to be a male, was then transported to Marineland of Florida. It is unknown what happened to the whale, but it was still alive on 18 June 1969.


References


External links


The Beaked Whale Resource

Beaked whales - into the abyss
- BBC News article
Diving with Beaked Whales
- A Whale Trackers documentary video. {{DEFAULTSORT:Beaked Whale Ziphiids Extant Miocene first appearances Taxa named by John Edward Gray