One of the more puzzling phenomena in the natural world is why whales strand themselves. Every year, there are a handful of circumstances when either groups or individual whales and dolphins converge upon the beaches of the world. Distressingly, many do end up perishing, however some, often with the help of humans, survive the ordeal and make it back the safer waters. There are many theories as to why whales beach themselves, here are some of the more plausible notions.
There are certain cetaceans that are more prone to stranding themselves. Pilot whales, beaked whales and sperm whales are often associated with beaching deaths. In September 2020, approximately 470 pilot whales were stranded in Tasmania, and in 1918, 1000 pilot whales were stranded on the Chatham Islands in New Zealand, this was the largest whale stranding ever recorded.
While some whales die at sea and then subsequently wash up on beaches, it is the instances where numerous individuals die together that baffle the public. Scientists have presumed that there are many possibilities to the phenomena;
Changes in the water temperature
As water temperature changes throughout the worlds oceans krill and fish, the main source of whale food, are beginning to adapt and subsequently seek either colder, or warmer waters. Whales unaware of the dangers of this adaptation may take larger risks to feed, for example swimming into shallower bays where prey may be congregating.
There is sufficient evidence that active sonar use leads to beaching. Regularly documented, there are correlations between cetacean stranding’s and military sonar weapons testing, deep sea dredging and oil rig drilling activities. Necropsies by marine biologists found internal injuries in stranded cetaceans, a factor that relates to a 2001 study conducted by the Bahamas Marine Animals Research Organization. The study found thatmid-frequency sonar affects Cuvier’s beaked whales most commonly, and in turn caused decompression sickness, leading to tissue damage from gas bubble lesions within individuals. This sickness could happen because the sonar causes the whales to panic and surface too quickly to escape. Mass beaching’s of beaked whales almost exclusively occur alongside sonar testing.
Navigational error is a rarity among whales and dolphins due to the fact that they possess excellent awareness, however, when sick or distressed, a whale can get lost and accidently strand. Whales, like humans and elephants have a strong social system and often wont leave a dying or stranded member. It is believed that groups of whales will stay close to a beached whale and then, tragically, beach themselves.
Hunting method’s may also be a factor to blame for accidental stranding. Orca’s are known for grounding seals onto beaches in Patagonia, now while this may be a hunting tactic that has proven successful for the Orca, there are individuals that have miscalculated their approach to the beach and become stuck, and consequently died when the tide retreats.