In the past, before alarm clocks were invented, what did people depend on to wake them up in the morning? Roosters.
“ A rooster’s crow symbolizes the break of dawn in many countries,” Takashi Yoshimura, professor at Nagoya University in Japan, told National Geographic. They are known to regularly crow two to three times at dawn.
However, scientists have long been unsure about why the animals do this. “It wasn’t clear whether crowing is under the control of a biological clock or is simply response to external stimuli.”
Roosters do react to the environment-such as car headlights-at any time of day. So it was previously thought that the increasing light in the morning might be the trigger for roosters’ crowing.
But Yoshimura and his colleagues now claim to have finally figured out the reason-roosters don’t need morning light to know when to start crowing; they will crow at the same time every day regardless of whether they can see dawn breaking.
In the study, which was published in the journal Current Biology, researchers placed 40 roosters in a soundproof, windowless room under dim lighting for 24 hours. But this didn’t deter the roosters. No matter what, they kept crowing in the morning just before dawn.
“It is proof that the behavior is caused by circadian rhythm”, said Yoshimura. In short, the roosters are genetically programmed to crow at a certain time every 24 hours.
Most animals, as well as plants, have such an internal time-keeping system. That’s why we tend to eat, sleep and exercise at around the same time every day. By consciously being aware of the schedule, our body has a chance to adapt to it, so keeping a regular biological clock is often tied to good health.
This experiment is the first of its kind to investigate the timing of roosters’ crowing. Kristen Navara, a scientist at the University of Georgia in the US who was not involved in the study, said that she wasn’t sure why no one had taken a closer look at this well-known phenomenon before.
“I think this is a very interesting study and something that should have been done a long time ago.” said Navara.
【小题1】What has been recently discovered to make roosters crow in the morning？| A．External stimuli like noises. | B．Their biological clocks. |
| C．Exposure to morning light. | D．Increased temperature. |
| A．Prevent. | B．Attract. | C．Encourage. | D．Upset. |
| A．Roosters have the same circadian rhythms as humans. |
| B．Following our biological clocks is good for our health. |
| C．Dark conditions can have some effect on roosters’ crowing. |
| D．Roosters’ biological clocks will change to help them adapt to the environment. |
| A．Worthless. | B．Meaningful | C．Boring. | D．Unscientific. |
