Why do some animals build structures and others don’t? And how do animals decide where to build? Animal homes need to be safe and secure, protected from predators and the weather. An eagle’s nest can weigh up to one ton, a termite mound can stand eight feet tall, and some falcon nest sites have been around for centuries. Going above ground and under, NATURE investigates just what goes into making a home when you’re wild and cost is not a factor.