How many stars can you see in the night sky? If the answers are “just a few” or “none”, you might be living with light pollution.

Light pollution happens when too much man-made light harms nature and people. Scientists have found that it is especially harmful to nocturnal（夜间的）animals.

Nocturnal animals sleep in the day and are busy at night. Animal scientist Christopher Kyba said man-made light is “the biggest change” humans have brought to these animals.

Small animals use darkness to hide from predators（捕食者）. But, he said, cloudy skies near cities are now “hundreds of times” brighter at night. This means that, for example, cats can catch more rats. Then, there will be too many cats and not enough rats to feed them all.

Baby sea turtles are born on beaches in the nighttime. They find the water by the light of the ocean horizon（地平线）. Man-made lights lead them away from the ocean. In Florida alone, “a large quantity of baby sea turtles die in this way every year,” said the US-based International Dark-Sky Association.

Also, birds that travel or hunt at night need moonlight and starlight. Man-made light can lead them in the wrong direction. Every year, a large number of birds die by flying into brightly-lit buildings.

It is often said that dogs are “mans’ best friends “But for some children in China, this idea has taken on an even deeper meaning.

Wu Qi, a dog trainer（驯养师）in Shanghai, started the Paw for Heal(PFH)program in China about eight years ago. The program trains dogs for animal-assisted therapy （动物辅助治疗）. ________ They also help people with mental illnesses（精神疾病）.

In Shanghai, the dogs have been trained to help kids with autism. Autistic（自闭的）children are easily confused（困惑的）or scared by their environments. But when the PFH dogs are around, they feel much more calm.

Pet owners can train their pets to become therapy dogs through PFH. Although this training is difficult (only 20 percent of dogs end up passing the program), it also helps a lot of people.

“She(my dog)makes me happy every day, and I think she can bring happiness to other people in need as well pet owner Wang Rui said in a report by Sixth Tone.

Animal-assisted therapy is new to China. But Wu has high hopes for the future, as he is now working together with a Scottish（苏格三的）university to improve his program.

“Through learning from the European team, China may shorten the time to catch up with Western countries in this field by several decades（几十年）. “Wu said in the Sixth Tone report

These days a video from the Beijing Wildlife Zoo has been going viral (走红). It shows a dog playing with lions and tigers four to five times its size! Is the dog in danger? Of course not. 【小题1】 Animals make friends with members of a different species (物种).

A zookeeper said that they raised the dog together with the lions and tigers when they were very young. 【小题2】 If you think this is too amazing, just remember that people have made friends with animals for a long time. 【小题3】 Maybe you have a pet yourself.

There are some other stories of cross-species friends. At an animal center, a cat named Marina and a pig named Laura became friends after they came to the center. 【小题4】 They grew up in the wild (野外) without their mothers’ care. They were close to each other and played happily together when they first met.

Why can different species be friends? In the wild, animals are busy hunting for their food. They have to work hard to keep themselves safe and protect their families. 【小题5】 When they needn’t do these things, animals will not have much to do. So it’s possible for them to make friends with members of other species.