What is causing whales from the deep sea to beach themselves?

The decomposing carcass of a humpback whale was roped off from tourists and beachgoers after it was spotted on 15 November at the Ipanema beach in Rio de Janeiro. With around 103 whales being stranded across Brazil alone in 2017, a natural question to ask would be: why do whales beach themselves?

Beaching, or cetacean stranding, is the phenomenon of aquatic mammals stranding themselves on land, usually on a beach. As many as 2,000 mammals beach themselves accidentally every year.

Whales that get beached often die of dehydration, collapse under their own weight, or drown when high tide covers their blowholes.

A report in Forbes explains that whales stranded on land dehydrate quickly without the water they are accustomed to. They easily suffocate under their own weight, which is normally supported by water around them.

Unlike other beached mammals like the dolphin, most stranded whales end up dying. Marine experts find it difficult to get the huge mammals back into the water before they die out of dehydration or other issues.

Human hand in deaths

While there is no clear explanation for whales stranding themselves on beaches, scientists speculate humans may be responsible in some way. An increasing amount of man-made materials and chemicals are polluting the oceans, leading to these aquatic mammals being born with deformities, and their early deaths.

Marine biologists and scientists also speculate that sonars from military boats may be interfering with the whale's brain wave activity, leading them to become disoriented or sick and forcing them to swim towards shallow waters where they end up beaching themselves.

Changes caused by global warming is also thought to be a reason for the beaching of whales as they go into unfamiliar waters in search of food.

Just like the 30-tonne whale carcass found at the Ipanema beach in Rio de Janeiro, many whales also wash ashore after they are dead.

Whales are also considered to be very social creatures and they often travel in large pods or groups. In very rare circumstances, some groups may unknowingly follow a sick or disoriented whale towards shallow waters leading to beaching, experts think.

On 10 February, the Department of Conservation (DOC) discovered 416 pilot whales had beached themselves overnight at Farewell Spit in Golden Bay in New Zealand and the beach was littered with the carcasses of nearly 300 of them.

Since 1840, more than 5,000 whales and dolphins have beached themselves on the shores of New Zealand, DOC records reveal.