It has been a week of heartbreak on New Zealand's Farewell Spit, with an unexpectedly happy twist. In two separate mass strandings, more than 650 pilot whales beached themselves on the thin strip of land — and over 350 of those died there over the past few days. When volunteer rescuers left the beach for the night Saturday, hundreds of survivors from the second stranding remained ashore. Then something curious happened: When the people returned Sunday morning, almost all the surviving whales were gone. All but 17 had left the beach and returned to the waters of Golden Bay overnight. "We had 240 whales strand yesterday in the afternoon and we were fearful we were going to end up with 240 dead whales this morning," Herb Christophers, a spokesman for New Zealand's Department of Conservation, told Reuters . "But they self-rescued, in other words the tide came in and they were able to float off and swim out to sea." At high tide Sunday, volunteers managed to send the remaining 17 survivors