More than 400 pilot whales stranded on a beach in New Zealand overnight, with 250 to 300 of the cetaceans already dead this morning in what is considered the third-largest whale beaching in the country since record-keeping began in the 1800s. A New Zealand Department of Conservation worker saw the whales in the water Thursday night (Feb. 9) local time, finding the whales sprawled across the beach this morning along Farewell Spit, a narrow strip of land on the South Island. More than 500 volunteers have come out to help with the rescue effort, with images showing people pouring water on the whales and covering them with what look like ripped T-shirts. DOC staff and volunteers tried to refloat more than 100 of the live whales when the tide came in at 10:30 a.m. local time today (Feb. 10); about 50 whales swam into the bay successfully, while 80 to 90 of them re-stranded on the beach, according to a statement by the DOC. Another refloating attempt is scheduled for Saturday (Feb. 11) at noon, during high tide, according to the DOC. The staff don't interact with the whales when it's dark for safety reasons: Pilot whales can get agitated when they're stressed and a flick of a fin or tail can injure or even kill a human, the DOC said. "They also carry diseases, so people need to avoid contact with blowhole exhalent or body fluids," the DOC said. As for why whales land themselves on the beach and in large groups is a mystery, with a number of theories put forth by marine mammal experts, from malfunctions to their onboard "GPS," to a genetic pull toward the land, to a follow-the-pod-leader behavior. Pilot whales, which are social animals, are well-known for stranding in groups of just a few to several hundred individuals, according to the American Cetacean Society. This would support the idea that when one pod member gets sick and ends up on dry land, the others swim to its aid, according to the DOC. A member of the dolphin family, pilot whales use echolocation to get around, and if that ability is disrupted it could also lead to a stranding. "The most likely hypothesis is that pilot whales' echolocation is not well-suited to shallow, gently sloping waters, because they generally prefer high relief (steep) areas such as the edge of the continental shelf," according to a DOC fact sheet. "This would also explain why most mass strandings happen in summer, when the whales follow popular food sources inshore." And Farewell Spit is located on the north end of Golden Bay, a known hotspot for pilot whale strandings. The largest mass stranding of pilot whales in New Zealand occurred at another hotspot - Chatham Islands, where 1,000 whales stranded in 1918, and then in 1985, some 450 individuals landed on the beach. NASA scientists have launched a study of a more far-out idea: that solar storms mess with the internal compasses of whales and dolphins, leading to stranding events. Experts at Massey University are expected to undertake animal autopsies, or necropsies, of some of the pilot whales today, according to the DOC. Due to the stranding, the Civil Aviation Authority of New Zealand is restricting airspace over the Farewell Spit Nature Reserve, barring any planes, drones or helicopters from flying under 2,000 feet (600 meters) there.