The frog that freezes solid and comes back

The Alaskan wood frog has a winter plan that sounds like science fiction: letting itself freeze. When the cold arrives, up to two-thirds of the water in its body turns to ice. Its heart stops, it stops breathing and its brain activity switches off.

The trick lies in chemistry. Before it freezes, its liver floods its cells with glucose and urea, which act as antifreeze and stop ice crystals from bursting them from within. The water freezes between the cells, not inside them, so the tissues hold out for months below zero.

When the thaw comes in spring, the heart starts beating again within hours and the frog hops off to croak as if nothing had happened. An animal that dies a little every year and comes back to tell the tale.