Nat Geo - Back before alarm clocks jolted us awake to greet the morning with bleary-eyed confusion, roosters performed that daily duty. Now, a new study shows that roosters don't need the light of a new day to know when it's dawn—rather, their internal clocks alert them to the time.
While researchers at Nagoya University in Japan were studying the genetic underpinnings of innate vocalizations—or nonlearned behaviors such as crowing—in chickens, they discovered that the male birds don't need external light cues to know when to start crowing. (Also see "Night Owls Stay Alert Longer Than Early Birds.")
"To our surprise, nobody [has] demonstrated the involvement of the biological clock in this well-known phenomenon experimentally," study co-author Takashi Yoshimura, who specializes in biological clocks at Nagoya University, said in an email.