A cape made from porous fibers traps heat and hides a bunny from night-vision cameras. The hairs of a polar bear have a hollow core, which reflects back IR emissions from the animal’s body. This structure helps prevent heat loss and keeps the bears warm in their Arctic environments.But the hairs have an added advantage: They can conceal the bears from thermal imaging cameras used in many night-vision devices. Textiles that can mimic polar bear hair’s IR-reflecting abilities might be useful in stealth applications, such as concealing soldiers. Previous attempts to make synthetic versions of the hairs have produced fibers that are too weak to be practically useful.