The animals of the forest and the fish in the pond have gone to sleep for the winter.  They are hibernating.  Animals hibernate because food is scarce in the winter and it's too cold to be walking around.  The tops of ponds and streams freeze as well as the ground.  Many animals dig holes deep in the ground and curl up for a long winter sleep.  Frogs bury themselves in mud at the bottoms of the deepest parts of ponds.  Bears sleep for most of the winter in caves.