About 14, 000 years ago, human beings and dogs began a partnership that has lasted through the years. Our interactions may have begun when wolves came close to our homes, attracted by the smell of human garbage, or when humans found wolf puppies and trained them to be loving pets.

Today, by means of the careful selection of dog parents, humans have created many different breeds of dogs. Each breed has its own look and talents, and its own role within human society. Here are three examples of “a dog's life” in the human world.

Many hospitals let specially trained dogs in to bring love and cheer to patients. Shaynee, the wheaten terrier, is a therapy dog. She visits children who are fighting deadly diseases. Dogs like Shaynee help patients feel calm and at peace, which can be hard in a busy hospital. They help both children and adults stay strong during long hospital stays, and, some suggest, even help them get better.

Today, some beagles work in airports for the government. They are part of a program called the Beagle Brigade. A beagle is good for this type of work because of its powerful nose, and ability to track smells. The Beagle's job is to smell everything that comes into the country. They caution officers about illegal fruits, vegetables, and other foods in luggage or in mail. The beagles do the job far better than any human can. Some of the dogs are donated by owners; others are rescued from animal shelters.

While some dogs are working hard, others are free to spend their days resting and playing. Across the world, many pet dogs are treated like children. Many have their own rooms and all the things a dog could want. Some, like the Yorkshire terrier pictured aside, even have their own clothes. Some of these pampered pets spend their days playing, learning to obey, or even going to yoga (or doga) classes. Their owners give them the best, and enjoy doing so.

Whether as workers or objects of affection, dogs have become beneficial to humans in many ways. There are plenty of advantages for the dog, too. Many species of wild dogs have nearly disappeared from the Earth. However, the domestic dog's special place as “man's best friend” has allowed it to survive in a human world.

Chen Guanghui is a guardian for black-necked cranes(黑颈鹤) in the Dashanbao Black-necked Crane National Nature Reserve of Zhaotong city, in southwest China’s YunnanProvince. Whistling(吹口哨) is the secret language Chen uses to communicate with the black-necked cranes, a type of migratory bird under first class protection in China. She says different whistles signal different things. When she whistles in an increasing tone, she tries to tell the cranes: ask your companions to come back for lunch, and they would chirp(吱喳叫)to spread the message right away.

Living near the Dashanbao Nature Reserve, a major winter habitat(栖息地) for the rare species, Chen started to take care of them in 2003, a mission she took over from her mother, whose devotion dates back to the 1990s.

“In the first few days, I remembered they ran away as soon as I approached them. I was very upset and asked my mom to come back, and I was worried they would starve,”   says Chen. “I initially tried everything, even singing folk songs to attract them, but failed. Later, I used special whistles and gradually formed close bond with the cranes. ”

“I treat them as if they were my own children, and I’m always concerned about them, especially during snowy days when they can’t get food. I feel uncomfortable and anxious when I hear them chirp and usually rush to prepare corn for them. ” It’s never been an easy job, and Chen has sustained quite a few injuries over the years, even falling into frozen marsh(沼泽)while trying to save a trapped crane in 2008. However, she never gave up. With love and responsibility, she has persisted in caring for the cranes for about 20 years.

Thanks to the joint protection efforts of Chen and staff members at the nature reserve, now more than 1,900 black-necked cranes overwinter in the area each season every year, up from about 300 when the nature reserve was established.

After nearly 20 years of efforts, China has built a monitoring network for endangered Siberian tigers and Amur leopards, covering more than 12,000 square kilometers in the provinces of Jilin and Heilongjiang, an expert said on Sunday.

With cutting-edge technologies such as artificial intelligence and big data, more than 4,000 infrared (红外线的) camera video clips of tigers and more than 600 clips of leopards were recorded by a team led by Jiang Guangshun, deputy director of the Feline Research Center of the Natural Forestry and Grassland Administration.

“By comparing the data of tigers and leopards of China and Russia from 2013 to 2015, we have confirmed that 17 tigers and 42 leopards are shared populations of both China and Russia,”Jiang said at the International Forum on Tiger and Leopard Transboundary Conservation which kicked off on Sunday in Harbin, Heilongjiang province. “The ecology has greatly improved since the natural forest protection project started in 1998, and all commercial logging has been stopped, which helped to protect tigers and leopards,”he said.

“However, we still face great challenges,”he said. “The distribution pattern of the two species suggests that the protection of the tiger and leopard requires the establishment of a network of protected sites, the construction of international and domestic corridors and the formation of a permeable landscape. It needs attention and support from all over the world. ”

“Military fences, transportation facilities and farmland in habitats have a strong impact on tigers’ free migration in different areas in China and cross-border areas between China and Russia. Living in small and isolated areas may cause more inbreeding, which can be a factor in their decline in immunity,” Jiang added.

Focusing on big cats around the world, especially tiger and leopard populations, the two-day event attracted more than 300 representatives from 19 countries. Representatives discussed monitoring technology, restoration of populations and habitat areas, landscape resource allocation in protected areas, conflict resolution and other related technical and policy issues.