Cryogenic wood frogs

Does anyone know what makes wood frogs freeze in the winter?

probably all that goo around them,it couldn't get back to the hole (it's home) in time,or fell asleep when it got cold enough.

Eh, Heres the answer I think. Its been away since I learned how the did that...anyway
Like all amphibians, frogs are cold-blooded, meaning that their body temperatures change with the temperature of their surroundings. When temperatures drop, some frogs dig burrows underground or in the mud at the bottom of ponds. They hibernate in these burrows until spring, perfectly still and scarcely breathing. Wood frogs can live north of the Arctic Circle, surviving for weeks in a frozen limbo state. This frog uses glucose in its blood as a kind of antifreeze that concentrates in its vital organs, protecting them from damage while the rest of the body freezes solid.

Maybe they just forget to pay the heating bill?

Thank you very much.