Stranding can be grouped into several types. The most obvious distinctions are between single and multiple standings.
Possible reasons why whales beach themselves are:
Injuries from collisions with boats, ships and other man-made aquatic machines.
Water pollution: Whales can become sick or poisoned due to pollutant chemicals such as gas and acid, and from the accumulation of daily waste created from everyday living.
Confusion due to man-made Sonar:
- Some biologists and scientists speculate that whales may become disoriented, sick and confused by the man-made sonar which may interfere with a whale’s brainwaves or use of echolocation causing the whale to lose its sense of direction and beach itself.
- The large and rapid pressure changes made by loud sonar can cause haemorrhaging.
Natural diseases: Just as humans suffer from sickness and natural diseases marine mammals may also be subject to natural diseases beyond their or our control.
Attacks from sharks or other marine mammals: Whales may beach themselves to escape or find cover from shark attacks or attacks from other marine mammals such as the killer whale.
Poison from various aquatic species: While it is more difficult to find adequate information regarding whales being poisoned by other aquatic species it is possible that a whale could become poisoned and disoriented causing it to swim to shore.
Changes or abnormalities in the earth’s magnetic field: Some biologists believe that abnormalities caused by changes in the earth’s magnetic field may interfere with a whale’s biological navigation causing it to lose its sense of direction.
Pneumonia: Just as humans get Pneumonia so do whales and there are recorded cases of whales swimming to shore as a result of catching Pneumonia.
Traumas caused by various aquatic elements in the environment: Whales generally have a good sense of direction and are excellent swimmers but there are some instances when a whale may collide with a large natural element (i.e.: a large rock) in its environment causing it to become injured and disoriented.
Changes in the weather and ocean caused by global warming: Changes in the tides, melting icebergs and shifting food sources such as fish may force whales to relocate and wander off course causing them to swim into shallow waters or possibly even beach themselves.
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.
“Follow-me” stranding: Some stranding may be caused by larger cetaceans following dolphins and porpoises into shallow coastal waters. The larger animals may habituate to following faster-moving dolphins. If they encounter an adverse combination of tidal flow and seabed topography, the larger species may become trapped.
- Over 140 pilot whales have died after beaching themselves on Stewart Island in New Zealand.
- Cetacean stranding is common; some 2,000 are beached every year on average around the world. Many beaching occurs in New Zealand every year.
What is 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.
- 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.
A beached whale carcass should not be consumed as it causes health risks.