Structures created by animals other than humans, most commonly by various mammals, birds, insects, and arachnids, occasionally by fish, reptiles, amphibians, crustaceans, mollusks, annelids, marine filter feeders, and others. Building materials may be collected material or self-secreted material. Animals create structures primarily to make protected habitats for thermo-regulation and safety from predators, to trap prey, and for display between members of the same species.
