Birds that are literally half-asleep — with one brain hemisphere alert (警惕的) and the other sleeping — control which side of the brain remains awake, according to a new study of sleeping ducks.

Earlier studies have documented half brain sleep in a wide range of birds. The brain hemispheres take turns sinking into the sleep stage characterized by slow brain waves. The eye controlled by the sleeping hemisphere keeps shut, while the wakeful hemisphere’s eye stays open and alert. Birds also can sleep with both hemispheres resting at once.

Decades of studies of bird flocks led researchers to predict extra alertness in the more vulnerable, end of the row sleepers.

Sure enough, in the end birds tended to watch carefully on the side away from their companions. Ducks in the inner spots showed no preference for gaze direction.

Also, birds dozing at the end of the line resorted to single hemisphere sleep, rather than total relaxation, more often than inner ducks did. Rotating (轮换位置) 16 birds through the positions in a four duck row, the researchers found outer birds half asleep during some 32 percent of dozing time versus about 12 percent for birds in internal spots.

“We believe this is the first evidence for an animal behaviorally controlling sleep and wakefulness simultaneously in different regions of the brain,” the researchers say.

The results provide the best evidence for a long-standing guess that single-hemisphere sleep evolved as creatures scanned for enemies. The preference for opening an eye on the lookout side could be widespread, he predicts. He’s seen it in a pair of birds dozing side-by-side in the zoo and in a single pet bird sleeping by a mirror. The mirror side eye closed as if the reflection were a companion and the other eye stayed open.

Useful as half sleeping might be, it’s only been found in birds and such water mammals (哺乳动物) as dolphins, whales, and seals. Perhaps keeping one side of the brain awake allows a sleeping animal to come up occasionally to avoid drowning (溺死).

Studies of birds may offer unique insights into sleep. Jerome M. Siegel of the UCLA says he wonders if birds’ half brain sleep is “just the tip of the iceberg”. He guesses that more examples may turn up when we take a closer look at other species.

For the history of life on Earth, organisms have relied on the light of the sun, moon, and stars to find their way and schedule their lives. While the beginning of electric lighting in the late 19th century may have benefited humans, it has caused problems in the natural world. Among the impacts of artificial light at night(ALAN), light pollution lures migrating birds to cities with shocking consequences, contributes to the alarming decline in insect populations, and convinces sea turtle babies to amble(缓行)away from the water instead of towards it.

Now, a new study from the University of Plymouth adds another disappointing finding about how ALAN is affecting the creatures with whom we share the planet: Light pollution from coastal cities can trick corals(珊瑚)into reproducing outside of the optimum times when they would normally reproduce.

Using a combination of light pollution data and spawning(产卵)observations, researchers were able to show for the first time that corals exposed to ALAN are spawning one to three days earlier and closer to the full moon compared to those on unlit corals. “That shift may reduce the survival and fertilization success of gametes(配子)and genetic connectivity between nearby lit and unlit coral systems,” they explain.

“Corals are among the most biodiverse, economically important, and threatened ecosystems on the planet,” write the authors of the study.

“Climate change has led to mass bleaching(褪色)events. Habitat destruction, fisheries, and pollution have reduced corals substantially since the 1950s,” they write, adding, “The complete loss of corals is anticipated over the next 100 years.”

If we want to reduce the harm ALAN is causing, we could perhaps look to delay the switching-on of night-time lighting in coastal regions to ensure the natural dark period between sunset and moonrise when coral reproduction remains undisturbed.

Spider webs have something in common with guitar strings. The long, thin strings on a guitar can vibrate(振动). They move back and forth, or from side to side. So do webs made by spiders. The lines of silk they produce can carry vibrations. This movement gives the small creature information about what landed on the web.

Spiders have eight legs and usually eight eyes. The animals build webs with their own soft, naturally-made silk. Spiders catch their food, usually insects, in their web. They make small movements, which spread across their web. The vibrations can tell the spider what is there—maybe something tasty to eat.

Vibrations give the spider details about what is caught in the web. They can tell the spider where that next meal is, and what it might be. But vibrations are not just used to identify what is for dinner. A spider makes its own vibrations to find out the condition of the web.

How do the researchers know that? They used special equipment to send out laser pulses into the web of a garden cross spider. Then they used a laser to measure the very small vibrations, which spread through the web.

Using computer models, the scientist could show how a spider can change the size of a wave vibration. The spider does this by changing the tightness of the silk lines. The spiders then can control how information is getting to them where they hang out in the middle of the web. In a way, spiders can move their silk threads, much like a musician plays the strings of a guitar.

Engineers might be able to learn a thing or two from spiders. This information could help engineers better understand how structures react to energy, and how vibrations affect a building.