On the morning of February 10th, more than 400 pilot whales were found stranded in New Zealand, on a crescent of beach ironically named Farewell Spit. When rescuers arrived, 300 whales had already died. Over 500 volunteers have arrived to assist with the rescue effort, organized by Project Jonah. Although they were able to re-float approximately 100 whales, they re-stranded later on the next day along with members from a second pod. The current number of stranded whales is estimated to be around 600, making it the largest cetacean stranding in decades. 1000 whales were stranded on the Chatham Islands in 1918, and 450 in Auckland in 1985.
At present, the cause of the strandings is unknown. Beached whales are not uncommon in this area; it is thought that the shallow, murky waters can confuse the whales, leaving them vulnerable to stranding if the tide recedes. Mass strandings are most common in odontocetes (toothed whales) that inhabit deep waters and live in tightly knit social groups. The social bond of these animals is so strong that when one animal becomes ill and strands, and the other whales in the group will follow. Strandings have also been linked to anthropogenic activity such as offshore oil exploration and military sonar. It is thought that this high-intensity noise can damage the hearing of cetaceans that depend on sonar to navigate through the oceans, or cause them to panic and surface too quickly, resulting in nitrogen gas bubbles in their blood. Pathologists are currently conducting necropsies to try to determine what could have caused the death of such a large number of whales.
You can read more about mass strandings and a new method that has been developed in Scotland to visualize noise-induced hearing loss in cetaceans here.