Using specialized parts of their bodies for tools and working with materials they find around them or produce organically, some animals construct spectacular structures that provide them with shelter, safety, and easy access to food. Their anatomy has evolved over generations to help them in their efforts to build their ideal homes. Without its fast-growing teeth, a beaver could not cut the wood to build its lodge; without its unusual type of saliva, a cave swiftlet could not create its crystal nest; and without silk glands, a spider could not weave its geometric home. When it comes to building homes, anatomy counts. Here’s a look at a few animals featured in The Animal House, and the anatomical features they possess that allow them to build their home sweet homes.