question: How do whales and other aquatic animals get beached ?
comment: Sometimes already dead animals just end up washing ashore. Other reasons can include the necessity for relocation, because of lack of food, changes in tides or fleeing attacks from other animals. Sometimes echolocation can also be disrupted by manmade things. They move to shallow waters and end up beaching themselves. There's no definite answer yet, but there's a lot of possibilities and speculations.
passages: Cetacean stranding
  
  Cetacean stranding, commonly known as beaching, is a phenomenon in which whales and dolphins strand themselves on land, usually on a beach. Beached whales often die due to dehydration, collapsing under their own weight, or drowning when high tide covers the blowhole. Several explanations for why cetaceans strand themselves have been proposed, but none have so far been universally accepted as a definitive reason for the behavior. A link between the mass beaching of beaked whales and use of mid-frequency active sonar however has been found.
  
  Section::::Species.
   Section::::Causes.:Intentional.
  
  In Argentina, killer whales are known to hunt on the shore by intentionally beaching themselves and then lunging at nearby seals before riding the next wave safely back into deeper waters. This was first observed in the early 1970s, then hundreds times more since within this pod. This behavior seems to be taught from one generation to the next, evidenced by older individuals nudging juveniles towards the shore, and can sometimes also be a play activity.
  
  Section::::Causes.:Sonar.
   Every year, up to 2,000 animals beach themselves. Although the majority of strandings result in death, they pose no threat to any species as a whole. Only about ten cetacean species frequently display mass beachings, with ten more rarely doing so.
  
  All frequently involved species are toothed whales (Odontoceti), rather than baleen whales (Mysticeti). These species share some characteristics which may explain why they beach.
   A stranding is when a cetacean leaves the water to lie on a beach. In some cases, groups of whales strand together. The best known are mass strandings of pilot whales and sperm whales. Stranded cetaceans usually die, because their as much as body weight compresses their lungs or breaks their ribs. Smaller whales can die of heatstroke because of their thermal insulation.
  
  The causes are not clear. Possible reasons for mass beachings are:
  
  BULLET::::- toxic contaminants
  
  BULLET::::- debilitating parasites (in the respiratory tract, brain or middle ear)
  
  BULLET::::- infections (bacterial or viral)
  
  BULLET::::- flight from predators (including humans)
   Section::::Disposal.
  
  If a whale is beached near an inhabited locality, the rotting carcass can pose a nuisance as well as a health risk. Such very large corpses are difficult to move. The whales are often towed back out to sea away from shipping lanes, allowing them to decompose naturally, or they are towed out to sea and blown up with explosives. Government-sanctioned explosions have occurred in South Africa, Iceland, Australia and Oregon, United States. If the carcass is older, it is buried.
   Whales have beached throughout human history; many strandings can be attributed to natural and environmental factors, such as rough weather, weakness due to old age or infection, difficulty giving birth, hunting too close to shore, or navigation errors.
  
  In 2004, scientists at the University of Tasmania linked whale strandings and weather, hypothesizing that when cool Antarctic waters rich in squid and fish flow north, whales follow their prey closer towards land. In some cases predators (such as killer whales) have been known to panic other whales, herding them towards the shoreline.
   A drift whale is a cetacean mammal that has died at sea and floated into shore. This is in contrast to a beached or stranded whale, which reaches land alive and may die there or regain safety in the ocean. Most cetaceans that die, from natural causes or predators, do not wind up on land; most die far offshore and sink deep to become novel ecological zones known as whale fall. Some species that wash ashore are scientifically dolphins, i.e. members of the Delphinidae family, but for ease of use, this article treats them all as "drift whales". For example, one species notorious for mass strandings is the pilot whale, also known as "blackfish", which is taxonomically a dolphin.
   In a few Japanese villages, the false killer whale is killed in drive hunts using sound to herd individuals together and cause a mass stranding or corral them into nets before being killed.
  
  Section::::Beachings.
   There is evidence that active sonar leads to beaching. On some occasions cetaceans have stranded shortly after military sonar was active in the area, suggesting a link. Theories describing how sonar may cause whale deaths have also been advanced after necropsies found internal injuries in stranded cetaceans. In contrast, some who strand themselves due to seemingly natural causes are usually healthy prior to beaching:
   A beached whale carcass should not be consumed. In 2002, fourteen Alaskans ate "muktuk" (whale blubber) from a beached whale, resulting in eight of them developing botulism, with two of the affected requiring mechanical ventilation. This is a possibility for any meat taken from an unpreserved carcass.
  
  Section::::Large strandings.
  
  In 1918, approximately 1000 pilot whales were stranded on the Chatham Islands, the largest whale stranding ever recorded.
  
  In 1985 about 450 pilot whales were stranded in Auckland, New Zealand.
   Long-finned pilot whales are the most common species involved in mass strandings. The largest event consisted of 1,000 whales on the Chatham Islands in 1918. Though mass strandings of this species are most common in New Zealand, pilot whales have beached themselves in many other countries in places such as northern Europe, the Atlantic coast of North America, South America, and southern parts of Africa.
  
  Over 600 pilot whales were involved in a recent stranding at Farewell Spit, New Zealand (February 9, 2017). This was the second largest mass stranding event to be documented.
  
  Section::::Strandings.:Research from strandings.
   On 14 January 2017, a pod of around 100 beached themselves in Everglades National Park in Florida, and the remoteness of the area was detrimental to rescue efforts, causing the deaths of 81 whales. The other two strandings in Florida were in 1986 with three beached whales from a pod of 40 in Cedar Key, and 1980 with 28 stranded in Key West.
  
  Section::::Conservation.
   Many cetacean species have been documented as drift whales, but some are more common than others. In New England, for example, the carcasses of fin, humpback, sperm, right, and pilot whales, as well as dolphins, are most likely to drift ashore. Some species have a naturally high buoyancy, and float when they are dead, aided by the gases of putrefaction.
   Beaching (nautical)
  
  Beaching is the process in which a ship or boat is laid ashore, or grounded deliberately in shallow water. This is more usual with small flat-bottomed boats. Larger ships may be beached deliberately, for instance in an emergency, a damaged ship might be beached to prevent it from sinking in deep water. Some vessels are designed to be loaded and unloaded by beaching; vessels of this type used by the military to disembark troops under fire are called landing craft.
   In November 2018, over 140 whales were witnessed stranded on a remote beach in New Zealand and had to be euthanised because of their declining health condition. In July 2019, nearly 50 long-finned pilot whales were found stranded on Snaefellsnes Peninsula in Iceland. However, they were already dead when spotted. 
  
  Section::::See also.
  
  BULLET::::- Dolphin drive hunting, a technique which herds small cetaceans towards the shore for slaughter
  
  BULLET::::- Drift whale
  
  BULLET::::- Marine Mammal Stranding Center
  
  BULLET::::- Saint-Clément-des-Baleines - A coastal area on French island Île de Ré named after mass strandings of whales
   Climate change influences the major wind systems and ocean currents, which also lead to cetacean strandings. Researchers studying strandings on the Tasmanian coast from 1920–2002 found that greater strandings occurred at certain time intervals. Years with increased strandings were associated with severe storms, which initiated cold water flows close to the coast. In nutrient-rich, cold water, cetaceans expect large prey animals, so they follow the cold water currents into shallower waters, where the risk is higher for strandings. Whales and dolphins who live in pods may accompany sick or debilitated pod members into shallow water, stranding them at low tide. Once stranded, large whales are crushed by their own body weight, if they cannot quickly return to the water. In addition, body temperature regulation is compromised.
   Strandings can be grouped into several 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, currents or winds may carry them to a coastline. Since thousands of cetaceans die every year, many become stranded posthumously. Most carcasses never reach the coast and are scavenged or decomposed enough to sink to the ocean bottom, where the carcass forms the basis of a unique local ecosystem called whale fall. Single live strandings are often the result of illness or injury, which almost inevitably end in death in the absence of human intervention.
   On 15 January 2009, an 18-metre (59 ft) fin whale stranded and subsequently died on a beach in Courtmacsherry Bay, after becoming disorientated and lured by unusually high tides. Efforts were made by Courtmacsherry Lifeboat to get the whale back into the sea but a combination of its size and weight meant that attempts to save the whale's life were unsuccessful. The whale was featured in a Channel 4 documentary "Inside Nature's Giants" which showed autopsies of large mammals.
   After a great storm, Daniel, Gracie and the Birdman discover a beached narwhal and attempt to get it back into the sea, but it is too heavy. The other narwhals gather in the bay and the Birdman knows that soon they will come to the beach themselves and then the curse of Samson will begin again on Bryher.
   The overwhelming majority of the cetaceans involved in sonar-associated beachings are Cuvier's beaked whales ("Ziphius cavirostrus"). This species strands frequently, but mass strandings are rare. 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 came from stranded animals. The first to publish research linking beachings with naval activity were 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 each time the Spanish Navy was conducting exercises. Conversely, there were no mass strandings at other times. They did not propose a theory for the strandings. A letter to "Nature" by Fernández "et al." in 2013 reported that there had been no further mass strandings in that area following a 2004 ban by the Spanish government on military exercises in that region.
   Section::::Death of whales.
   The academia is not sure of the causes of death of the whales. "It's definitely unusual. But what may be the cause we can't put our finger on," said A.K. Armah, a lecturer at the University of Ghana, who studies marine life.
   Whales that live in the pelagic ocean, far from the continental shelf, are less likely to wash up ashore than coastal species. Once these deep-sea animals do find themselves in shallower waters, however, they may run into difficulties, as the gradual shelving of the shoreline is thought to play a role in confusing their sense of echolocation. Sperm whale strandings are known to have occurred in the North Sea for centuries, and the incidents may be increasing with louder ship noise.
  
  Section::::Overview.:Reasons.
   Whale fall
  
  A whale fall is the carcass of a cetacean that has fallen onto the ocean floor at a depth greater than , in the bathyal or abyssal zones. They can create complex localized ecosystems that supply sustenance to deep-sea organisms for decades. This is unlike in shallower waters, where a whale carcass will be consumed by scavengers over a relatively short period of time. It was with the development of deep-sea robotic exploration that whale falls were first observed in the late 1970s.
   A 2017 study by scientists from Germany's University of Kiel suggests that large geomagnetic disruptions of the Earth's magnetic field, brought on through solar storms, could be another cause for whale beachings. The authors hypothesize that whales navigate using the Earth's magnetic field by detecting differences in the field's strength to find their way. The solar storms cause anomalies in the field, which may disturb the whales' ability to navigate, sending them into shallow waters where they get trapped. The study is based on the mass beachings of 29 sperm whales along the coasts of Germany, the Netherlands, the UK and France in 2016.
  