A
beached whale is a
whaleWhale is the common name for marine mammals of the order Cetacea. The term whale is sometimes used to refer to all cetaceans, but in more common English usage it generally excludes the members of the Delphinoidea superfamily, such as dolphins and porpoises...
which has become stranded on land, usually on a beach. Beaching is often fatal for whales, as they become
dehydratedDehydration is defined as excessive loss of body water. It is literally the removal of water from an object. In physiological terms, it entails a relative deficiency of water molecules in relation to other dissolved solutes...
and die. Some die when their lungs are suffocated under their own weight or drown when high tides cover their
blowholesthumb|250px|right|The single blowhole of a [[bottlenose dolphin]] just before going under againIn biology, a blowhole is the hole at the top of a Cetacean's head through which the animal breathes air. It is homologous with the nostril of other mammals. As whales reach the water surface to breathe,...
.
Species
Every year there may be beachings adding up to 2000 animals. Although the majority of strandings will result in death, they pose no threat to the species as a whole. Of all of the species of cetaceans, only about 10 species are frequently involved in mass beachings, with a further 10 species rarely being involved. All of the frequently involved species are
toothed whaleThe toothed whales form a suborder of the cetaceans, including sperm whales, beaked whales, orca, dolphins, and others. As the name suggests, the suborder is characterized by having teeth, rather than baleen as do animals in the other suborder of cetaceans, Mysticeti...
s (
Odontocetes), meaning that none of the
baleen whaleThe baleen whales, also called whalebone whales or great whales, form the Mysticeti, one of two suborders of the Cetacea . Baleen whales are characterized by having baleen plates for filtering food from water, rather than having teeth. This distinguishes them from the other suborder of cetaceans,...
s are regularly involved in beachings. These species share some characteristics which may explain why they beach. Body size does not normally affect the frequency, but both the animals' normal habitat and social organization do appear to influence their chances of coming ashore in large numbers. Odontocetes that normally inhabit deep waters and live in large, tightly knit groups are the most susceptible. They include the
Sperm whaleThe sperm whale, , is a species of marine mammal in the order cetacea, a toothed whale with the largest brain of any animal. The whale was named after the milky-white waxy substance, spermaceti, found in its head and originally mistaken for sperm...
, a few species of
PilotThe pilot whale is either of two species of cetacean in the genus Globicephala. The genus is part of the oceanic dolphin family although their behaviour is closer to that of the larger whales. The two species are the Long-finned Pilot Whale and the Short-finned Pilot Whale. The two are not readily...
and
OrcaThe Killer Whale or Orca , or less commonly, Blackfish, is the largest species of the dolphin family. Most people think that they are whales, but they are actually dolphins. They are called killer whales often because they sometimes hunt whales for food...
whales, a few
beaked whaleA 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...
s and some
oceanic dolphinOceanic dolphins are the members of the Delphinidae family of cetaceans. These aquatic mammals are related to whales and porpoises. They are found worldwide, mostly in the shallower seas of the continental shelves...
s. Solitary species are naturally excluded from mass strandings. Cetaceans that spend most of their time in shallow, coastal waters are almost never mass stranded, with
porpoisePorpoises are small cetaceans of the family Phocoenidae; they are related to whales and dolphins. They are distinct from dolphins, although the word "porpoise" has been used to refer to any small dolphin, especially by sailors and fishermen...
s being essentially immune.
Overview
Strandings can be grouped into several different types. The most obvious distinctions are between single and multiple strandings. The carcasses of deceased cetaceans are likely to float to the surface at some point; during this time,
currentAn ocean current is a continuous, directed movement of ocean water generated by the forces acting upon the water, such as the wind, Coriolis force, temperature and salinity differences and tides caused by the gravitational pull of the Moon and the Sun...
s or
windWind is the flow of air or other gases that compose an atmosphere . On Earth, wind consists of the bulk movement of air...
s may carry them towards a coastline. Since thousands of cetaceans must die every year it is natural that many will become stranded. Most cetacean deaths will involve only a single individual, causing these strandings to consist of just one animal if a stranding occurs at all. However, most whale carcasses probably never reach the coast and are
scavengedScavenging, or necrophagy, is a carnivorous feeding behaviour in which a predator consumes corpses or carrion that were not killed to be eaten by the predator or others of its species. Scavengers play an important role in the ecosystem by contributing to the decomposition of dead animal remains...
or decomposed enough to sink to the bottom of the ocean, where the carcass forms the basis of a unique local ecosystem called
whale fallWhale fall is the term used for a whale carcass that has fallen to the ocean floor. Whale falls were first observed in the 1980s, with the advent of deep-sea robotic exploration....
. Single live strandings are often the result of an illness or injury, which would almost inevitably end in death unless a passer-by knows how to react.
Multiple strandings of dead animals in one locality are rare and often cause a great deal of media coverage as well as rescue efforts by sympathetic humans. Even multiple offshore deaths are unlikely to lead to multiple strandings due to the variable winds and currents scattering the animals across the sea. A key factor in many of these cases appears to be the strong social cohesion amongst toothed whales. If one whale gets into trouble, its distress calls may prompt the rest of the pod to follow and become beached themselves. There is no definitive specific cause for mass strandings. Instead they may happen due to numerous factors that can act in combination. Many have been proposed, with some seeking to explain only a subset of cases; however, they are difficult to prove conclusively and are sometimes controversial.
Natural
Whales have been found beached throughout human history so many strandings can be attributed to natural and environmental factors. There could be many natural reasons like rough weather, weakness due to old age or infection, difficulty giving birth, hunting too close to shore and navigational mistakes. A single stranded animal can prompt the entire pod to respond to its distress signals and become stranded. In 2004, scientists at the
University of TasmaniaThe University of Tasmania is a public Australian university based in Tasmania, Australia. Officially founded on 1 January 1890, it was the fourth university to be established in nineteenth-century Australia...
found a link between whale strandings and the weather. It is hypothesised that when cool
AntarcticThe Antarctic is the region around the Earth's South Pole, opposite the Arctic region around the North Pole. The Antarctic comprises the continent of Antarctica and the ice shelves, waters and island territories in the Southern Ocean situated south of the Antarctic Convergence...
waters rich in squid and fish flow north, whales follow their prey closer towards land making them more prone to stranding. In some cases predators (such as killer whales) have been known to panic whales, herding them towards the shoreline.
Another proposed cause is that the
echolocationEcholocation, also called biosonar, is the biological sonar used by several animals such as dolphins, shrews, most bats, and most whales. The term was coined by Donald Griffin, who was the first to conclusively demonstrate its existence in bats...
system used by many whales can have difficulty picking up very gently-sloping coastlines. This theory accounts for mass beaching hot spots such as
Ocean Beach, TasmaniaOcean Beach is a long stretch of beach running north of Macquarie Heads and Hells Gates on the West Coast of Tasmania. It is close to Strahan and parallel to the Strahan Airport runway...
and Geographe Bay, Western Australia where the slope is about half a degree (approximately 8m deep one kilometer out to sea). The
BioacousticsBioacoustics is a cross-disciplinary science that combines biology and acoustics. Usually it refers to the investigation of sound production, dispersion through elastic media, and reception in animals, including humans. This involves neurophysiological and anatomical basis of sound production and...
group at the
University of Western AustraliaThe University of Western Australia is the oldest university in the state of Western Australia. Established in February 1911, it is the only university in the state to be a member of the prestigious Group of Eight, as well as the Sandstone universities. The University was established under and is...
has done research indicating that repeated reflections between the surface and ocean bottom in gently-sloping shallow water may attenuate sound so much that the echo is inaudible to the whales. Stirred up sand as well as long-lived microbubbles formed by rain may further exacerbate the effect.
A controversial theory, researched by
Jim BerklandJim Berkland is a retired geologist who worked many years for the U.S. Geological Survey. He was also the first County Geologist for Santa Clara County and was in that position for twenty-one years. He has published over fifty scientific papers. He has been a popular guest on many network news...
, a former
geologistFor other uses, see Geologist .A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth and terrestrial planets...
with the U.S. Geological Survey, attributes the strange behaviour to radical changes in the
Earth's magnetic fieldEarth's magnetic field is approximately a magnetic dipole, with the magnetic field S pole near the Earth's geographic north pole and the other magnetic field N pole near the Earth's geographic south pole...
just prior to earthquakes and in the general area of earthquakes. Berkland says when this occurs, it interferes with sea mammals' and even migratory birds' ability to navigate, which explains the mass beachings. He says even dogs and cats can sense the disruptions, which explains elevated rates of runaway pets in local newspapers a day or two before earthquakes occur. Research on
Earth's magnetic fieldEarth's magnetic field is approximately a magnetic dipole, with the magnetic field S pole near the Earth's geographic north pole and the other magnetic field N pole near the Earth's geographic south pole...
and how it is affected by moving
tectonic platesTectonic Plates is a 1992 independent Canadian film directed by Peter Mettler. Mettler also wrote the screenplay based on the play by Robert Lepage. The film stars Marie Gignac, Céline Bonnier and Robert Lepage.-Plot summary:...
and earthquakes is ongoing.
"Follow-me" strandings
Another possibility is that a proportion of strandings may be caused by larger cetaceans following dolphins and porpoises into shallow coastal waters. The larger animals may be familiar with faster moving dolphins in their area and become habituated to following them. If an adverse combination of tidal flow and seabed topography is encountered, the larger species are at much higher risk of being trapped.
Sometimes it may work the other way. A recent example of this occurred when a local dolphin was followed out to open water by two
Pygmy sperm whaleThe pygmy sperm whale is one of three species of toothed whale in the sperm whale family. They are not often sighted at sea, and most of what is known about the creatures comes from the study of washed-up specimens.- Taxonomy :...
s that had become lost behind a sandbar at Mahia Beach, New Zealand.
The possibility of training dolphins to lead trapped whales out to sea is an intriguing one in areas where frequent mass strandings occur, such as New England or Florida.
An interesting observation is that pods of killer whales, predators of dolphins and porpoises, are very rarely stranded. There may be two explanations for this - firstly that heading for shallow waters may be a very effective anti-predator mechanism for dolphins and that the killer whales have learned not to take the risk, or else that the killer whales have learned how to operate in shallow waters, particularly in their pursuit of seals. The latter is certainly the case in Península Valdés, Argentina, where a particular pod of killer whales pursue seals up shelving gravel beaches to the edge of the littoral zone. The pursuing whales are occasionally partially thrust out of the sea by a combination of their own impetus and retreating water and have to wait for the next wave to take them back out.
SONAR
There is evidence that active sonar may hurt whales and lead to their beaching. On some occasions whales have been stranded shortly after military sonar was active in the area , suggesting a link. Reasons as to how sonar may cause whale deaths have also been put forward by scientists after necropsies found internal injuries in stranded whales. In contrast, whales stranded due to seemingly natural causes are usually healthy prior to beaching.
Firstly, it has been argued that the very loud rapid pressure changes made by sonar can cause haemorrhaging. Evidence emerged after the beachings of seventeen whales in the Bahamas in March 2000 following a
United States NavyThe United States Navy is the sea branch of the U.S. Armed Forces. It is one of the seven uniformed services of the United States. As of 31 December 2008, the U.S. Navy had about 331,682 personnel on active duty and 124,000 in the Navy Reserve. It operates 283 ships in active service and more than...
sonar exercise. The Navy accepted blame in
this Joint Interim Report which found the dead whales to have experienced acoustically-induced haemorrhages around the ears. The resulting disorientation probably led to the stranding. Ken Balcomb, a zoologist, specializing in the study of whales, particularly the
OrcaThe Killer Whale or Orca , or less commonly, Blackfish, is the largest species of the dolphin family. Most people think that they are whales, but they are actually dolphins. They are called killer whales often because they sometimes hunt whales for food...
populations that inhabit the
Strait of Juan de FucaThe Strait of Juan de Fuca is a large body of water about long forming the principal outlet for the Georgia Strait and Puget Sound, connecting both to the Pacific Ocean...
between Washington and
Vancouver IslandVancouver Island is a large island in British Columbia, Canada, one of several North American regions named after George Vancouver, the British Royal Navy officer who explored the Pacific coast of North America between 1791 and 1794....
, has studied mass beachings of whales. He investigated the March 2000 beachings and argues that the powerful sonar pulses had used vibrations that
resonatedIn physics, resonance is the tendency of a system to oscillate at larger amplitude at some frequencies than at others. These are known as the system's resonant frequencies . At these frequencies, even small periodic driving forces can produce large amplitude vibrations, because the system...
with airspaces in the whales, causing tearing of tissue around the ears and brain.
Another means by which sonar could be hurting whales is a form of
decompression sicknessDecompression sickness describes a condition arising from the precipitation of dissolved gasses into bubbles inside the body on depressurisation...
. This was first raised by pathological examinations after 14
beaked whaleA 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...
s stranded in the
Canary IslandsThe Canary Islands are a Spanish archipelago which, in turn, forms one of the Spanish Autonomous Communities and an Outermost Region of the European Union. The archipelago is located just off the northwest coast of mainland Africa, 100 km west of the disputed border between Morocco and the...
. The stranding happened on 24 September 2002, close to the operating area of Neo Tapon (an international naval exercise) about four hours after the activation of mid-frequency sonar. The team of scientists found acute tissue damage from gas-bubble lesions, which are indicative of decompressions sickness. The precise mechanism of how sonar causes bubble formation is not fully known. It could be due to whales panicking and surfacing too rapidly in an attempt to escape the sonar pulses. There is also a theoretical basis by which sonar vibrations can cause supersaturated gas to nucleate to form bubbles.
The overwhelming majority of the whales that are involved in beachings associated with active SONAR tests are Cuvier's Beaked Whales (Ziphius Cavirostrus). This species of beaked whale strands frequently, but mass strandings are very rare. In fact they are so difficult to study in the wild that prior to the interest raised by the SONAR controversy, most of the information about them was gathered from stranded animals. The first scientific correspondence in a journal that linked beachings with military activy was written by Simmonds and Lopez-Jurado in 1991. They noted that over the past decade there had been a number of mass strandings of beaked whales in the Canary islands, and every time the Spanish Navy was conducting exercises. In addition there was no cases of mass strandings reported when the Spanish Navy was not conducting exercises. They did not propose a theory for the strandings, but the paper called for more research.
In May 1996 there was another mass stranding in Greece (West Peloponnese). At the time it was noted as "atypical" both because mass strandings of beaked whales is rare, and also because the stranded whales were spread over such a long stretch of coast with each individual whale spacially separated from the next stranding. At the time of the incident there was no connection made with active SONAR, the marine biologist investigating the incident, Dr. Frantzis, made the connection to SONAR because of a Notice to Mariners he discovered about the test. His scientific correspondence in Nature titled "Does acoustic testing strand whales?" was published in March 1998.
Dr. Peter Tyack of Wood's Hole Oceanographic Institute, has been researching the effect of noise on marine mammals since the 1970s. He has led much of the recent research on beaked whales (and Cuvier's beaked whales in particular). Data tags attached to the animals have shown that these whales dive considerably deeper than previously thought, and are in fact the deepest diving species of marine mammal. Deep dives are for hunting squid. Their surfacing behaviour is highly unusual because they exert considerable physical effort to surface at a controlled rate of ascent, rather than simply floating to the surface like sperm whales. Deep dives are also followed by three or four shallow dives. Vocalization behaviour is terminated at shallow depths (presumably because of fear of predators), and finally it was noted that pairs of whales are communicating in order to stay together at these depths where there is no light. It is hypothesized that the active SONAR is interfering with this process.
Unlike research on fish or plankton, theories involving marine mammals are sometimes difficult to test, because it is unethical to subject the animals to some stimulus that would cause permanent harm. Whales are deliberately exposed to sound sources under research permits in what is commonly called "controlled exposure experiments", but no researcher would cause a beaching to prove a theory. The elaborate dive patterns are assumed to be necessary to control the diffusion of gases in the bloodstream. There is no data that shows a beaked whale making an uncontrolled ascent or failing to do successive shallow dives. The lack of vocalization at the surface might be because of fear of predators. The whales may interpret the strange sound of a SONAR as a predator and break its normal pattern of behaviour in a way that is dangerous to the animal. This last theory would make mitigation particularly difficult since the whales may not be exposed to physically damaging sound levels, but only levels that cause fear. The damage mechanism would not be the sound.
Carcass
After a beached whale dies, it can become a source of
diseaseA disease or medical condition isan abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and signs...
and
pollutionPollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms . Pollution can take the form of chemical substances, or energy, such as noise, heat, or light...
. Due to the very high efficiency as thermal
insulatorInsulator may refer to: something with science* Insulator , a substance that resists the flow of electric current* Insulator , an element in the genetic code* Thermal insulation, a material used to resist the flow of heat...
of the
blubberBlubber is a thick layer of vascularized fat found under the skin of all cetaceans, pinnipeds and sirenians.-Description:Lipid-rich, collagen fiber-laced blubber comprises the hypodermis and covers the whole body, except for parts of the appendages, strongly attached to the musculature and skeleton...
, a whale carcass can keep its internal temperature over for up to three days, making it the ideal environment for
anaerobic microorganismsAn anaerobic organism or anaerobe is any organism that does not require oxygen for growth and may even die in its presence. There are three types: obligate anaerobes, which cannot use oxygen for growth and are even harmed by it; aerotolerant organisms, which cannot use oxygen for growth, but...
.
As they are very large, such corpses are difficult to move. There are reports of some cases where humans tried to
blow upExploding whale most often refers to an event at Florence, Oregon, in 1970, when a dead sperm whale was blown up by the Oregon Highway Division in an attempt to dispose of its rotting carcass. This incident became famous in the U.S...
the carcass with explosives, with unexpected side effects to spectators.
A whale
carcassCarcass may refer to:* Carcase the body of a slaughtered animal after the removal of the offal. It is also used in the King James Version of the Bible where there is reference to a human carcase....
should not be consumed. In 2002, fourteen
AlaskaAlaska is the largest state of the United States of America by area; it is situated in the northwest extremity of the North American continent, with Canada to the east, the Arctic Ocean to the north, and the Pacific Ocean to the west and south, with Russia further west across the Bering Strait...
ns ate
muktukMuktuk is the English word for the traditional, pre-agrarian, Inuit/Eskimo meal of frozen whale skin and blubber...
(whale blubber) from a beached whale, and eight of them developed symptoms of
botulismBotulism also known as botulinus intoxication is a rare but serious paralytic illness caused by botulinum toxin, which is produced by the bacterium Clostridium botulinum...
, two of them requiring
mechanical ventilationIn medicine, mechanical ventilation is a method to mechanically assist or replace spontaneous breathing.This may involve a machine called a ventilator or the breathing may be assisted by a physician or other suitable person compressing a bag or set of bellows...
. This is a possibility for any spoiled
meatMeat is animal flesh that is used as food. Most often, this means the skeletal muscle and associated fat, but it may also describe other edible tissues such as organs, livers, skin, brains, bone marrow, kidneys, or lungs...
, or meat taken from an animal which has been dead for some time without proper preservation of the carcass.
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