Whale beachings: some notable events

The mass stranding of more than 400 pilot whales on the beaches of New Zealand on Friday ranks among the worst in a nation accustomed to the phenomenon.

The cause of the beaching was unknown, though officials said the shallow bay and jutting hook shape of Farewell Spit, near Nelson, could have trapped the pod of Pilot whales.

New Zealand's Department of Conservation said it was the country's third-worst mass stranding; the biggest occurred when 1,000 whales beached at the remote Chatham Islands in 1918, followed by 450 that washed ashore in Auckland in 1985.

Here are other notable mass strandings of cetaceans from around the world.

- Argentina -

The International Whaling Commission says animals can swim to their deaths on shore, or die at sea and wash up on the beach later.

Strandings can occur for natural reasons, like age and disease, or from man-made disruption, such as environmental degradation or collision with ships.

One of the largest known mass beachings in the last century was of false killer whales in October 1946, when an estimated 835 false killer whales were stranded near Mar del Plata in Argentina.

- Chile -

In December 2015 more than 300 whales were discovered washed up on a remote Patagonian inlet in southern Chile. Scientists at the time called the sight of the stranding "apocalyptic".

A surge in algae in the water, known as a "red tide", was believed to be the culprit. It bloomed across the ocean around Chile in the early months of 2016, choking to death an estimated 40,000 tons of salmon in the Los Lagos region -- or some 12 percent of the country's annual production of the fish.

In July 2016 some 70 dead whales were also found on the southern Chile coast.

- Madagascar -

In May 2008 around a hundred whales swam onto the beaches of Madagascar and three quarters of them perished, in the first mass beaching blamed on high-frequency sonar mapping systems deployed in the hunt for oil.

According to a report released by the International Whaling Commission in 2013, the culprit was as a high-power 12 kilohertz multibeam echosounder system operated by an ExxonMobil vessel about 65 kilometres (40 miles) offshore. The company disagreed with the findings.

The use of anti-submarine sonars was also suspected of causing the mass-beaching of whales in 2002, when some 15 beaked whales perished in the Canaries after a NATO exercise.

- Japan -

In April 2015, around 150 melon-headed whales were discovered washed up on a stretch of beach in Japan.

The cetaceans, which usually live in deep water and are a member of the dolphin family, were thought to have either suffered from a parasitic infection that disrupted their ability to navigate, or had become unable to navigate in the sandy shoals.