Amazing animal engineers

Animals build an incredible array of structures in which to sleep, raise young, or catch prey.

Some structures involve excavating in subsoil or wood, others involve construction underwater, and some are fixed to trees.

This title explores how polar bears dig out caves in the snow to protect themselves from the coldest weather, how spiders spin webs of incredibly strong silk to ensnare prey, how prairie dogs dig underground 'towns' that can house hundreds of families, and much more.