In the third largest whale beaching event in the history of New Zealand, over 400 pilot whales washed up onto the country’s South Island last Thursday night, most of them dying before they could be sent back to the sea.
Almost 75 percent of the whales died before conservation workers and volunteers could reach Farewell Spit—a bay region in the island’s north tip that is notorious for whale beachings—on Friday morning.
Workers refloated about 130 of the surviving animals, with more than a third of them successfully escaping into deeper water. The other 80 whales swam back and re-beached, a common phenomenon that scientists believe results from an attempt to rejoin their original pod.
Because refloating can only be done during high tide, when the whales are submerged in the water, workers kept the re-beached whales alive by pouring water on them and covering them with sheets to protect them from the sun.
The following night, another pod of 240 whales beached in the same location and re-stranded themselves after volunteers attempted to return them to the sea. Most of these, however, were able to rescue themselves and swim out unaided when the tide came in the next day.
The series of beachings—affecting over 650 whales in total—added to Farewell Spit’s reputation as a hotspot for whale stranding. The bay’s geography, with a curved, hook-like coastline and beaches that gently slope into shallow water, is likely an important contributor. Some theories suggest that their gradual slopes and shape make it more difficult to navigate by echolocation, the whales’ primary means of finding their way underwater. The whales become confused in this treacherous location and swim in the wrong direction—towards the shore.
Other theories involve solar storms interfering with the magnetic fields whales may also use for navigation, or that shark attacks drive the animals to shallow waters. Because pilot whales are social animals, it is also possible that the entire pod follows when a sick or injured whale accidentally beaches itself, trying to help it return to safety.
(featured image courtesy of Bahnfrend, Wikimedia Commons CC BY-SA 3.0)