In September, something terrible happened on the west coast of Tasmania, Australia. As many as 380 pilot whales became stranded(搁浅) in shallow water there and later died. This might have been Australia's largest stranding event on record, the BBC reported.
But this large amount of whale stranding is not uncommon. For centuries, it has happened all over the world and has puzzled scientists. Scientists say the cause is often unknown. But they have offered many different explanations.
Some say the whales chase small fish for food and end up in shallow water because they are not paying attention to where they are going.
Others think the stranding has something to do with Earth's geomagnetic field (地磁场). They say that a geomagnetic compass in whales' brains controls their position. Unusual changes in Earth's magnetic field can affect the whales' compasses and send them in the wrong direction.
Another explanation suggests that stranding is caused by the close relationships that whales have. Pilot whales travel in large groups. One lead whale might mistakenly lead the whole group to shallow water. "And if one gets into trouble, the others will not leave," said Sheryl Gibney, a leading biologist from New Zealand. "Some will come in and try to help, they get trapped on the beach, then more will come."
The whales are trapped by mistake or out of sympathy(同情). Once they get stranded, they will likely die. According to the National Oceanic and Atmospheric Administration of the US, less than 10 percent of all stranded whales survive.
