Cetacean (Whale, Dolphin, Porpoise) Strandings


Few things in nature are more tragic than the sight of a pod of whales—some of the most magnificent and intelligent creatures on Earth—lying helpless and dying on the beach. Mass whale strandings occur in many parts of the world, and we don't know why. Scientists are still searching for the answers that will unlock this mystery.



Every year, thousands of whales, dolphins and porpoises get into trouble on coastlines around the world. Unless those animals that strand alive, or become trapped in shallow water, are responded to rapidly, they will become distressed and may die.


  • Cetacean stranding, commonly known as beaching, is a phenomenon in which cetaceans 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 of the stranding have been proposed, but none have so far been universally accepted as a definitive reason for the peculiar behavior


  • 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 10 cetacean species frequently display mass beachings, with 10 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.


In February 2017, over 400 pilot whales were stranded on a New Zealand South Island beach. Such events happen with some regularity in the area, suggesting that the depth and shape of the sea floor in that bay may be to blame.




















  • According to Project Jonah, a whale rescue group, New Zealand has one of the highest rates of whale strandings in the world, and on average, about 300 whales and dolphins beach themselves on Kiwi shores every year.


  • The reasons for whales strandings are still unclear, but it is thought a combination of factors contribute, with old, sick and injured whales being particularly vulnerable. Navigational errors among pods are also common, especially when chasing food or coming close to shore to avoid predators such as orcas.


  • Since 1840, more than 5,000 whales and dolphins have beached themselves on New Zealand shores according to DOC records.


  • In 1918, 1,000 whales beached themselves on the Chatham Islands, and in 1985 450 stranded at Great Barrier Island off the coast of Auckland.


  •  In 1985 about 450 pilot whales were stranded in Auckland, New Zealand. On June 23, 2015, 337 dead whales were discovered in a remote fjord in the Patagonia, southern Chile, which was the largest stranding of baleen whales to date


  • Nearly 100 false killer whales are currently stranded in the Everglades in the worst Florida stranding of its kind. (National Parks Service) 


  • Sudden, loud underwater noise can cause mass strandings and puts whales and dolphins at risk

  • WDC helps to rescue whales and dolphins that get washed up alive

  • The large numbers of whales, dolphins and porpoises found dead or stranded around the world's coastlines each year are often helpless, and usually die within a few hours or days if not attended to in the right way.

  • Those still alive will need an urgent and expert rescue response, but we also need to help prevent the many stranding incidents that result from man-made factors, such as noise pollution or entanglement in fishing nets.

  • Some animals die at sea and then wash up onshore, others come ashore (strand) alive, and some become trapped in shallow waters. Whatever the circumstances, a live whale or dolphin beached on the shore is almost always in danger. Some come ashore on their own, but others can strand in mass groups.

  • In the case of species that live in groups with strong social or ‘family’ bonds, a lead animal in trouble may put the whole group into danger.  Pilot whales are a good example. If one individual in the group is ill they may come in to help, but end up in trouble themselves.

  • Live stranded whales and dolphins may seem to be healthy but could be old or unwell. Others may have suffered injury from boat propellers or entanglement in fishing nets and gear.  Nets and fishing gear are the biggest killer of whales and dolphins across the globe, causing terrible injury and typically death by suffocation (because once trapped underwater the animals clamp their blow holes shut). Please see our section on fisheries for more information about this.

  • Errors in navigation may also be a cause but, noise from military exercises (using loud explosions or powerful sonar), or from exploration surveys at sea for oil and gas could also cause whales and dolphins to strand on the shoreline. Remember, they live in a world of sound – using it to communicate, find food, and navigate. High levels of noise disrupt this world and threaten these creatures.

  • Around 600 pilot whales recently became stranded on a New Zealand beach, around 400 of which died before volunteers could refloat them back into the sea. Sadly, this kind of mass whale stranding has occurred since human records began, and happens somewhere in the world on a regular basis.

  • At the end of 2015, 337 sei whales died in a fjord in Chile after the largest ever beaching of whales of this species. Mass strandings can also occur in northern Europe. In February 2016, 29 sperm whales were found stranded on the coasts of Germany, the Netherlands, eastern England, and northern France, a record for this species in the North Sea.

  • Why do these creatures, which are masters of living in a totally aquatic environment, enter an inhospitable land environment where inevitably some, if not all, will die?

  • Mass strandings almost invariably involve oceanic species of whales. Long-finned and short-finned pilot whales tend to be the most frequent casualties. Other species typically are false killer whales, melon-headed whales, Cuvier’s beaked whales and sperm whales. All of these normally live in waters over 1,000 metres deep and are very social, forming cohesive groups that in some cases may number hundreds of animals.

  • Although it’s tempting to automatically blame whale strandings on human activity, the fact that deep-dwelling species of whales most often get stranded, and in the same locations, indicates that in many cases natural causes are more likely to be to blame. Mass strandings of these oceanic species tend to be in very shallow areas with gently sloping, often sandy, seabeds. In those situations, it is no surprise that these animals, which are used to swimming in deep waters, can get into difficulties and even if re-floated will often re-strand.

  • The echolocation they use to aid navigation also does not work well in such environments. So it is quite possible that the majority of such strandings are simply due to navigational error, for example when whales have followed a valuable prey resource into unfamiliar and dangerous territory. This may have been the cause of the mass stranding of sperm whales in the North Sea, some of which had recently digested oceanic squid in their stomachs.

  • The ratio of strandings to sightings for sperm whales in the North Sea is significantly higher south of the Dogger Bank where shallow, often sandy, environments prevail. And the same goes for Farewell Spit, Golden Bay in the South Island of New Zealand, where the recent pilot whale stranding took place and where similar incidents have occurred several times in the last few years.

  • Both areas have seen a number of mass strandings of those particular species in the past. In the southern North Sea, there are records of mass strandings of sperm whales dating back at least to 1577.

  • In July 2105 some 25 out of 70 pilot whales that stranded in the Kyle of Durness in Sutherland died in what is believed to be Scotland's largest ever beaching of pilot whales. In November 2010, 35 whales were found dead on a beach in County Donegal in Ireland.

  • However, mass strandings aren’t only caused by whales getting lost or misjudging the depth of the water. One or more individuals may be diseased and, as they become weaker, they seek shallower waters so they can more easily come to the surface to breathe. Once their bodies come to rest on a hard surface for any extended period, there is a greatly increased chance that their chest walls will be compressed and their internal organs damaged.

  • There are many theories about why whales and dolphins sometimes swim into shallow water and end up stranding themselves on beaches in various parts of the world.

  • Some scientists have theorized that a single whale or dolphin may strand itself due to illness or injury, swimming in close to shore to take refuge in shallow water and getting trapped by the changing tide. Because whales are highly social creatures that travel in communities called pods, some mass strandings may occur when healthy whales refuse to abandon a sick or injured pod member and follow them into shallow water.

  • Mass strandings of dolphins are far less common than mass strandings of whales. And among whales, deep-water species such as pilot whales and sperm whales are more likely to strand themselves on land than whale species such as orcas (killer whales) that live closer to shore.

  • In February 2017, over 400 pilot whales were stranded on a New Zealand South Island beach. Such events happen with some regularity in the area, suggesting that the depth and shape of the sea floor in that bay may be to blame.

  • Some observers have offered a similar theory about whales pursuing prey or foraging too close to shore and getting caught by the tide, but this seems unlikely as a general explanation given the number of stranded whales that have turned up with empty stomachs or in areas devoid of their usual prey.


Does Navy Sonar Cause Whale Strandings?


  • One of the most persistent theories about the cause of whale stranding is that something disrupts the whales’ navigation system, causing them to lose their bearings, stray into shallow water, and end up on the beach.

  • Scientists and government researchers have linked the low-frequency and mid-frequency sonar used by military ships, such as those operated by the U.S. Navy, to several mass strandings as well as other deaths and serious injuries among whales and dolphins. Military sonar sends out intense underwater sonic waves, essentially a very loud sound, that can retain its power across hundreds of miles.

  • Evidence of how dangerous sonar might be for marine mammals emerged in 2000 when whales of four different species stranded themselves on beaches in the Bahamas after a U.S. Navy battle group used mid-frequency sonar in the area. The Navy initially denied responsibility, but a government investigation concluded that Navy sonar caused the whale strandings.

  • Many beached whales in strandings associated with sonar also show evidence of physical injuries, including bleeding in their brains, ears and internal tissues. In addition, many whales stranded in areas where sonar is being used have symptoms that in humans would be considered a severe case of decompression sickness, or “the bends,” a condition that afflicts SCUBA divers who resurface too quickly after a deep dive. The implication is that sonar may be affecting the whales’ dive patterns.

Other possible causes put forth for the disruption of whale and dolphin navigation include:

  • weather conditions;

  • diseases (such as viruses, brain lesions, parasites in the ears or sinuses);

  • underwater seismic activity (sometimes called seaquakes);

  • magnetic field anomalies; and

  • unfamiliar underwater topography.

Despite the many theories, and growing evidence of the danger that military sonar poses for whales and dolphins worldwide, scientists have not found an answer that explains all whale and dolphin strandings. Perhaps there is no single answer.




Mass strandings are alarming mysteries, and when they occur they make news all over the world. Often, it’s hard for scientists to determine just what is causing massive numbers of animals to get stuck in shallow waters.


Rescue methods are typically comprised of two methods using humans to “Herd” the whales out of shallow water. This only limited success because of th lack of human resource and the limitation of staning in water that in safe for humans

The second most typlical methos to get Cetecaens out of shallow water is by use of soud. Typically explosives are used to scare the whales.


Speaking from his office in Washington, D.C., Trevor Spradlin, a marine mammal biologist with NOAA's standing network, told National Geographic that the whales had been first reported by a group of fishermen. "We have a hotline number and there are well-established communication trees, so whenever someone sees a stranded marine mammal … eventually it winds up with us," said Spradlin. He added that a fisherman or a tourist on a beach will often call a local authority, such as a sheriff or a lifeguard, and then the news will make its way up a chain to NOAA. (See "Why Are Dolphins Dying on East Coast?")

Whale-Saving Network

The agency works with a network of professional biologists and volunteers across the country who are trained to respond to marine mammal strandings, through a program that was formalized by 1992 amendments to the federal Marine Mammal Protection Act. The network has a presence in all coastal states and reports to six regional coordinators and a national coordinator, who oversee the program and provide training and equipment.

In 2012, NOAA's network responded to more than 4,500 marine mammal strandings in the continental U.S., including Alaska. That number includes animals that were found dead, as well as animals found alive. Of the latter group, some were successfully pushed back out to sea, some were sent to rehab centers for treatment, and others were euthanized.

Spradlin said responders tend to see more stranded cetaceans (whales and dolphins) on the East Coast and more stranded pinnipeds (seals) on the West Coast. Many factors determine whether rescuers are successful in returning an animal alive to the water, said Spradlin, including the cause of the stranding in the first place, the animal's health and age, and environmental factors. Whales can get stuck in shallow water for a variety of reasons, including weakness from disease, hunger, or boat strikes; impacts of chemical or noise pollution; or social behavior.

Pilot whales are particularly at risk for group strandings, Spradlin said, because they are highly social animals that live in close-knit family groups, or pods. "Their need for group cohesion is very strong, so these animals stay together," said Spradlin. He added that scientists think a pod gets stranded after one animal first gets stuck, often an older or sick individual.

"The rest get caught up in tide fluctuations and they get lost, because they focus on being with the sick individual," said Spradlin. He added that such strong group cohesion can also be an asset to survival, because if the group can be freed, weaker individuals can receive protection and support from the stronger survivors.

Rescue Techniques

According to Spradlin, marine mammal rescuers rely on a range of techniques and technology, both of which have been improving over the past few decades. He added that working in marine environments faces the challenges of remote locations, corrosive saltwater, and fluctuations in weather and temperature.

But veterinary medicine for marine mammals in distress, in particular, is improving, said Spradlin. "The quality of care has improved significantly, and we've been able to train more people around the country to be responders, so we have a more robust network with better equipment," he said.

Spradlin said rescuers often use sound to try to move stranded marine mammals to deeper water. They often play back recordings of the animals' own calls, to try to lure them out. Or they play the sounds of their predators, to try to scare them away.

"Rescuers may bang on pipes, an old fisherman technique that puts sound in the water," added Spradlin. "It doesn't hurt them, but it can cause the animals to want to avoid the area."

Spradlin said biologists will also try to herd the animals out to sea with their boats, which he noted make sound and release bubbles.

If the animals are beached, the rescue attempt gets a lot harder. Depending on the animal's size and physical condition, people may try to move it into the water. "It's dependent on the availability of equipment, like heavy movers, slings, cranes, and things like that, and in remote areas it's almost impossible getting such equipment there in time," he said.

Healthy animals have a better chance of surviving a beaching. "Cetaceans are designed to live in water, so when they are stranded on a beach their internal organs aren't used to having that weight on them and they start getting crushed," said Spradlin. So when it comes to a rescue, "time is usually of the essence."

Volunteers are trained to keep stranded marine mammals cool and wet as long as possible, if moving equipment isn't immediately available. If the machinery doesn't arrive in time, or if the animal is severely compromised, "it's often best to euthanize it or it will have a very painful, slow death," said Spradlin.

Learning From Strandings

Spradlin stressed that NOAA and other scientists try to learn from each stranding that is reported.

The agency distributes tags through its network, with the goal of marking every animal that is successfully released. Electronic tags that beam information on the animal's whereabouts through satellites are preferred, Spradlin noted, although they aren't always available, so scientists may use a simple metal tag instead, often attached to a dorsal fin. "If they are seen later by a scientist or fisherman, they can report that the animal is ok," said Spradlin.

Animals that do perish are studied, with an eye toward better understanding the species and identifying the causes of its death.

Spradlin added, "Marine mammals are still fairly foreign to us. We know a lot more about terrestrial mammals, but marine mammals are so hard to study at sea."

When it comes to strandings, Spradlin said there can be many factors behind the problem. "If it is a human-caused situation, by pollution or things humans are doing to the marine environment, then those are things we have a responsibility to fix."