Why Whales and Dolphins Beach Themselves: Causes, Consequences, and Conservation
Unraveling the mysteries behind stranded whales and dolphins, and what their beachings reveal about the ocean’s delicate balance.
Why Whales and Dolphins Beach Themselves
Beachings of whales and dolphins — also known as cetacean strandings — have perplexed humans for centuries. These events, sometimes involving solitary animals and sometimes vast pods numbering in the hundreds, are tragic and dramatic reminders of the vulnerability of marine mammals. Despite decades of research, the root causes are not always clear, though scientists have identified a complex tapestry of environmental, biological, and human-driven factors. This article explores the leading theories and evidence, responses to stranding events, and what these incidents tell us about ocean health.
What Is Cetacean Stranding?
Cetacean stranding refers to marine mammals washing ashore or becoming trapped in shallow water where they cannot survive for long. While beachings can involve many species, they are most common among toothed whales (Odontoceti), including dolphins, pilot whales, and sperm whales. Strandings result in considerable numbers of deaths each year — estimates suggest up to 2,000 global incidents annually — yet these figures pose no immediate threat to species survival. Still, the loss of individuals is significant both ecologically and emotionally for those who witness such events.
- Single strandings usually involve diseased, injured, or old individuals.
- Mass strandings are events where multiple cetaceans, sometimes entire pods, beach themselves together.
- Both types can arise from a variety of direct and contributory causes.
Main Theories and Causes of Stranding
Despite advances in marine biology, no single theory can explain all whale and dolphin beachings. Instead, researchers agree that strandings likely result from multiple, overlapping factors:
Natural and Biological Causes
- Disease and Infection: Sick or parasitized animals become weak or disoriented, leading them close to shore, where they may strand and die. Pathogens, heavy parasite loads, or even injuries can play a decisive role.
- Old Age: As with many animals, the elderly are more vulnerable and may end up stranded as a terminal event. Weakness, slowed reactions, and reduced foraging ability all contribute.
- Birthing Complications: Difficult or premature births can lead to mothers or calves stranding, especially since calving often takes place in shallow waters.
Environmental Factors
- Weather and Water Conditions: Storms, rough seas, or unusual currents can push whales and dolphins off course or into unfamiliar shallows, resulting in accidental strandings.
- Geomagnetic Disturbances: Recent research suggests that solar storms and geomagnetic anomalies can disrupt whales’ ability to navigate using Earth’s magnetic field. Disoriented whales may head into shallow waters and become trapped.
- Prey Movements: When prey such as squid or fish move closer to shore, predators like pilot or sperm whales may follow, increasingly risking beaching.
- Predator Panic: Large predators like orcas can sometimes chase or panic smaller whales into shallow waters or unfamiliar coves.
- Coastal Topography and Echolocation Errors: Gently-sloping beaches and sandy shores can interfere with whales’ echolocation. Whales relying on sound may not perceive gradual shallows in time, especially when underwater noise is compounded by rain, bubbles, or sediment.
Social and Behavioral Factors
- Social Bonds: Some cetacean species have strong social cohesion. If a leading or stressed individual becomes stranded, pod members may follow, leading to mass strandings.
- Distress Calls: When one whale is in distress, others may respond and cluster together, compounding the risk of group strandings.
- Intentional Stranding for Hunting: Uniquely, some orcas intentionally beach themselves to catch seals or other prey onshore. They rely on waves to return to the sea and are rarely stranded by accident, as this risky behavior is taught and refined within family pods.
Human-Driven Causes
- Ship Noise and Naval Sonar: Activities such as military sonar and offshore seismic exploration produce intense underwater sounds that can disorient or even physically harm whales, prompting them to swim erratically and sometimes strand en masse.
- Chemical and Plastic Pollution: Ingestion of marine litter or exposure to harmful chemicals can sicken marine mammals and trigger strandings. For example, necropsies on stranded whales have revealed digestive tracts blocked by plastics or suffering from toxin buildup.
- Habitat Degradation: Coastal development and changing sea conditions can create new hazards for navigation and foraging, increasing the risks of beaching.
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Which Species Are Most Affected?
Although all whale and dolphin species have been recorded stranding, the phenomenon is particularly pronounced among the toothed whales (Odontoceti):
| Species/Group | Stranding Pattern | Habitat Type |
|---|---|---|
| Pilot whales | Mass strandings common | Deep-water, social groups |
| Sperm whales | Solitary and group strandings | Deep-water, migratory |
| Beaked whales | Susceptible to sonar-induced mass strandings | Deep-water |
| Dolphins | Both single and group strandings | Varied |
| Orcas (Killer whales) | Rare, intentional but sometimes accidental | Varied, highly adaptive |
What Happens to Stranded Whales and Dolphins?
Once stranded, whales and dolphins face physiological stresses their bodies are not equipped to handle on land:
- Dehydration: Unlike terrestrial mammals, stranded cetaceans lose moisture rapidly.
- Organ Collapse: The sheer body mass of large whales exerts crushing force on their organs when unsupported by water.
- Drowning: A rising tide may cover their blowholes, causing suffocation.
- Overheating: Their blubber, which insulates them in cold seas, can lead to heat stress under the sun.
- Predation and Scavenging: Beached animals may fall prey to scavengers before they die.
In rare, well-coordinated rescues, whales and dolphins may be returned to the water, especially small or otherwise healthy individuals. However, mass strandings are sadly often fatal for most involved. In some tragic cases, if animals cannot be relieved, authorities may choose euthanasia to avoid prolonged suffering.
Historical and Global Context
Historical evidence indicates strandings have occurred for centuries, with prehistoric humans scavenging from beached whales as far back as 14,000 years ago. Today, recorded strandings occur worldwide, but certain hotspots—like Tasmania, Western Australia, South Africa, and parts of the United States—see regular incidents, partly due to local geography and prevailing ocean conditions.
Case Studies: Notable Strandings and Their Lessons
1. Sperm Whales in the North Sea (2016)
In early 2016, the mass stranding of 29 sperm whales along European shores coincided with intense solar storms. These geomagnetic disturbances are widely believed to have disoriented the whales’ navigation systems.
2. Pilot Whales in Tasmania and New Zealand
Large pods of pilot whales have stranded repeatedly on the shallow beaches of Tasmania and New Zealand, likely due to a combination of echolocation challenges, prey movements, and social cohesion; if one whale heads for shore, many will follow.
3. Orca ‘Intentional Stranding’ in Argentina
In Argentina, a population of orcas has learned to intentionally beach themselves to hunt seals on land, a risky but generally controlled behavior passed down from older to younger whales. These whales rarely become stranded by accident.
4. Plastic Ingestion: Florida Keys, 2022
FWC researchers found a 47-foot sperm whale that stranded after ingesting marine debris, blocking its digestive tract and causing lethal emaciation.
How Do Scientists Investigate Strandings?
Understanding why a stranding occurred involves forensic investigation, called a necropsy (animal autopsy). Experts examine:
- Body condition (injuries, malnourishment, disease symptoms)
- Stomach contents (for evidence of starvation, plastic ingestion, or toxicity)
- Acoustic trauma (damage to auditory tissues from sonar or explosions)
- Parasite and pathogen loads
- Environmental data (geomagnetic records, sonar activity, shipping, storms)
Can Strandings Be Prevented?
Some beachings are likely unavoidable, as natural deaths and navigation errors are part of life for wild cetaceans. However, scientists are working to reduce human-driven causes by:
- Regulating naval sonar and seismic testing in sensitive areas
- Reducing marine pollution and plastic waste
- Monitoring and managing high-risk stranding sites
- Developing rapid response and rescue techniques
Conservation Implications
While regular strandings may not threaten most cetacean species with extinction, each incident is a tragedy for individual animals and their social groups. Mass strandings, especially of endangered species, are cause for concern and valuable opportunities for research. The health of whales and dolphins is linked to the broader health of ocean ecosystems, and their struggles on shore often highlight problems in the seas — from rising noise pollution and climate change to mounting plastic and chemical contamination.
Frequently Asked Questions (FAQs)
Q: Are whale and dolphin strandings a modern phenomenon?
A: No. Archaeological evidence suggests that humans were scavenging stranded cetaceans at least 14,000 years ago. However, modern factors such as noise pollution and plastics have added new threats.
Q: Can stranded whales survive if returned to the sea?
A: Survival depends on the whale or dolphin’s health and the efficiency of the rescue. Seemingly healthy, recently stranded animals sometimes recover, but many die soon after due to underlying illness, injury, or stress.
Q: Why do whales sometimes explode after stranding?
A: Decomposition inside a stranded whale produces gases that can build up and, if unrelieved, cause the animal to burst. This is a gruesome but natural process of decay.
Q: Are certain beaches more prone to strandings?
A: Yes. Gently sloping beaches with fine, sandy bottoms may interfere with cetacean echolocation, making them natural ‘stranding hotspots.’ Local geography, prey movements, and social factors also play a role.
Q: How can the public help stranded whales and dolphins?
A: Contact local wildlife authorities immediately if you witness a stranding and follow their instructions. Well-meaning but untrained intervention can sometimes cause more harm than good.
Key Takeaways
- Whale and dolphin strandings are complex events with biological, environmental, and human-driven causes.
- Mass strandings are most common among social, deep-water species such as pilot whales, dolphins, and some beaked whales.
- Despite the tragedy, strandings can provide vital scientific data for conservation.
- Human activities increase risk, but better policies and research can help reduce preventable strandings.
References
- https://wildlifeflorida.org/whales-beach/
- https://en.wikipedia.org/wiki/Cetacean_stranding
- https://www.discovermagazine.com/planet-earth/why-were-so-many-pilot-whales-stranded-last-year-and-will-it-continue
- https://pubmed.ncbi.nlm.nih.gov/16030851/
- https://iwc.int/management-and-conservation/strandings
- https://www.fisheries.noaa.gov/insight/understanding-marine-wildlife-stranding-and-response
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