This past summer, hundreds of fish in Canada beat the heat in human- made plumes (一股) of cold water. The approach could help protect cold-water species as climate change warms rivers.

Fish can become stressed or even die when the water gets too hot. In rivers, Atlantic salmon and other cold-water species sometimes escape the heat by flocking to cooler zones. Such chill sites may be found near groundwater springs or small rivers and streams flowing into larger waterways.

“People have done a lot to preserve and add to these natural shelters,” said Kathryn Smith, a civil engineer in Canada at Dalhousie University in Halifax, Nova Scotia. Her team works on the new river-chilling project. Until now, she says, “There hasn’t really been an emphasis if we can create cold-water habitat.”

To test the idea, her team pumped (抽送) groundwater from a nearby well into the Wrights River in Nova Scotia. The groundwater was 9℃. This created an artificial plume of cool water. It was up to 20℃ cooler than the surrounding water.

This plume attracted several hundred fish of different life stages and species. These included Atlantic salmon, most of which were very young. These small young fish hung out in the plume throughout the test. But when a heat wave raised river temperatures to about 30℃, older fish took shelter in the plume, too.

The team also tried a second approach. They rerouted some water from the river into an underground trench (沟渠). Here, the water cooled a bit before flowing back into the river. This method cooled part of the river without needing a pump. The water temperature fell by only a few degrees Celsius this way. But even so, fish were spotted in the cooled flow throughout the summer.

Though small, these early tests show a “proof of concept”. That means the approaches show promise but they aren’t yet ready for wide use. “More work lies ahead to decide the needed number of cooling site s to really help fish communities,” says Kathryn Smith.

Have you ever been hungry and sleepy and wished you could solve both problems at once? If you were a reindeer (驯鹿) , it would be easy. According to a new research, these talented deer can have a snooze while they eat their food.

Reindeer live in the Arctic and other northern regions where the winters are extremely dark and cold. Food can be rare in winter, so during the warmer months the deer must eat as much as they possibly can.

Like cows, reindeer use a process called rumination (反刍) to break down the tough plant they eat. This process involves passing the food back and forth between their mouth and the four “stomachs”, chewing it repeatedly until all the nutrients (营养) have been absorbed. In summer, all that chewing seems to leave very little time for sleep.

To find out their secret to getting enough rest, scientists fitted four reindeer with devices that monitored their brain waves. While the reindeer were ruminating, their brain waves were similar to the patterns shown during sleep. The animals sat or stood quietly with their eyes closed, and they were less likely than usual to react to. the movements of a neighbouring deer. “They were in a very relaxed state, ” researcher Melanie Furrer said.

The chewing movement made it hard for the researchers to tell whether, the animals’ brain waves were truly in sleep mode. But when they tested the deer again after rumination, the animals' brain activity showed that they felt rested.

If reindeer are kept awake for too long, they need extra “recovery sleep” to catch up. After ruminating, however, the deer did not need as much recovery sleep. Study co-author Gabriela Wagner said that ruminating serves two different purposes at the same time —eating and sleeping.

When you praise a dog, it’s listening to not just the words you say but also how you say them. That might not be huge news to dog owners. But now researchers have explored this phenomenon by using an imaging machine to look inside the brains of 13 dogs as they listened to their owners’ voice.

The reward pathway in the dogs’ brains lit up when they heard both praising words and an approving intonation (语调)—but not when they heard random (随机的) words spoken in a praising tone or praising words spoken in a flat tone, according to the researchers.

“Dogs deal with both what we say and how we say it in a way which is amazingly similar to how humans do it,” says Attila Andics, a neuroscientist in Hungary. When dogs hear speech, he explains, they seem to separate the meaning of words from the intonation. Then the left hemisphere (半球) of the brain deals with meaning, while intonation is dealt with in the right hemisphere.

All the dogs in the study were willing volunteers and were trained not to move in the scanner (扫描器). The dogs could get up and leave the machine whenever they wanted. But it was clear to the dogs that their human companions loved it when they did this very easy task. “They were really happy to take part,” says Andics. “The difficulty of the training was that they can’t move more than 3 millimeters in any direction, otherwise we will have to throw out all of the data.”

He says most dog owners have experimented with trying to “trick” their dogs by saying nonsense words in a cheerful, happy tone of voice. “I think the big difference here is that they only heard us, and they didn’t see us,” says Andics, because the dogs were inside the machine. “Here, the only information they had was the speech signal. What we saw is that for praise to be dealt with as a reward, when there is no other supporting information, both word meaning and intonation have to fit.”