Old barn owls have young ears, still sharp at an age when mammals would be deaf, according to new research by Germany’s University of Oldenburg. This is because all birds can regrow damaged hair cells in the inner ear, while mammals have lost the ability to do so.

Barn owls (Tyto alba) locate and catch prey in darkness using their hearing alone, and their ears specialise in high frequencies—the region where humans and other mammals usually lose their hearing. When a range of barn owls of different ages were tested, all had flawless hearing—even an extremely old 23-year-old. Studies on elderly starlings and invertebrates have also shown inner-ear hair-cell regeneration. The human body has the ability to repair the ear’s vestibular system, which means that we retain our sense of balance, even in old age. Study author Ulrike Langemann says this suggests the genetic switch for hearing regeneration is still there in humans, but in “off-mode” for our inner-ear hair cells. The quest to switch it on is an active field of research.