Wise as an…Wait…Young as an Owl!!
The fact that outer hair cells in birds are regenerated naturally after the damage has been known for decades. Most of this knowledge has been accumulated through experiments where a bird’s hair cells are deliberately and carefully damaged using a toxic agent such as noise. Scientists then observe the regeneration of hair cells in the areas of damage and an approximate return of function. The restoration of function is documented through electrophysiological measures such as the ABR as well as behavioral measures. Perception of pure tones has been shown to return at all but the highest frequencies in birds after ototoxic damage to the hair cell population. However, the perception of complex acoustic stimuli does not appear to return to normal in a bird with regenerated hair cells. Interestingly though, songbirds that cannot perceive complex acoustic stimuli still proceed to learn song-based communication without a problem.
So, the question to be asked is whether avian hair cells regenerate only after induced damage or in a continuous manner, much like teeth in sharks? The answer seems to be in the affirmative. What was already evident in starlings has now been demonstrated in barn owls. Barn owls living in captivity appear to retain youth-like hearing even at the ripe old age of 23. These are the findings reported in a recent paper by Georg Klum, Christine Köppl and colleagues from the University of Oldenburg, Germany. Well, it turns out that owls may be wise and old in years but remain young in ears.
Krumm B, Klump G, Köppl C, Langemann U. Barn owls have ageless ears. Proc Biol Sci Sep 27:284(1863).