Modern zoos are different from those built fifty years ago. At that time zoos were places where people could go to see animals from many parts of the world. The animals lived in cages with iron bars (栅栏). Although the zoo keepers took good care of them, many of the animals did not feel comfortable，and they often fell ill.

In modern zoos, people can see animals in more natural conditions. The animals are given more freedom in larger places so that they can live as they would in nature. Even the appearance of zoos has changed. Trees and grass grow in cages, and water flows through the places the animals live in. There are few bars; instead, there is often a deep ditch (沟), filled with water, which surrounds a space where several sorts of animals live together as they would naturally. In an American zoo, the visitors can walk through a special huge cage that is filled with trees, some small animals and many birds, and large enough for the birds to live naturally. In a zoo in New York, with the use of special nights, people can observe certain animals that are active only at night, when most zoos are closed. Some zoos have special places for visitors to watch animals that live in the desert or under water.

Modern zoos not only show animals to visitors, but also keep and save rare animals. For this reason, fifty years from now, the grandchildren of today's visitors will still be able to enjoy watching these animals.

Dogs and humans clearly have a special bond. But do dogs, like humans, produce more tears at times when they are flooded with emotion? A new study, which may be the first to look at this question, says that, indeed, the eyes of dogs do well up with tears. In fact, it happens regularly when they’re reunited (团聚) with the owners.

“We found that dogs produce tears associated with positive emotions,” says Takefumi Kikusui of Azabu University in Japan. “We also made the discovery of a chemical, oxytocin, as a possible mechanism (机制) behind it.”

Kikusui and his colleagues made the discovery after one of his two dogs had babies 6 years ago. He noticed that, when his dog was nursing the babies, something changed in the dog’s face — there were tears. Those tears don’t fall as they often do in humans but they do get teary eyes. “That gave me the idea that oxytocin is likely to increase tears,” Kikusui says.

They decided to run a reunification experiment and see if oxytocin brought dogs to tears. First, they used a standard test to measure dogs’ tear volume (量) before and after reuniting with their owners. They found that tear volume indeed ascended when they got back together with the familiar human and not with a person they didn’t know. When they added oxytocin to the dogs’ eyes, their tear volume also increased. That finding supports the idea that the release of oxytocin plays a role in tear production when dogs and their owners get back together. They also asked people to rate pictures of dogs’ faces with and without artificial tears in them, and it turned out that people gave more positive responses when they saw dogs with teary eyes. These findings suggest that dogs’ tear production helps to develop stronger connections between people and their dogs.

Kikusui says they had never heard of the discovery that animals produce tears in joyful situations, such as reuniting with their owners, and that they were all excited that this would be a world first!

In the long dispute over whether dogs are smarter than cats, a recent study published in the journal Learning & Behavior suggests that dogs are no more exceptional than other animals when it comes to smartness and intelligence.

The news is sure to cause the debate among dog owners and scientists who study dog behaviors. The authors reviewed existing studies and data on animal cognition(认知) and found that while dogs are smart and trainable, they are not ＂super smart＂ , despite what most dog owners will tell you. Dog research was quite popular in the 1990s and continues to be so. When it came to other animals, though, scientific studies on intelligence were barely involved in, despite evidence to suggest that horses, chimpanzees(黑猩猩) and cats had tricks of their own. Almost everything a dog claimed to do, other animals could do too.

Researchers set out to test the supposition. They compared dog cognition with members of three similar groups: meat-eating animals, social hunters and farm animals. Among the animals they studied were wolves, cats, chimpanzees, dolphins, horses and pigeons. What they found was that ＂dog cognition does not look exceptional.＂ Dogs cannot use tools, unlike dolphins, New Caledonian crows and chimpanzees, which have been observed using plant stems to fish for termites(白蚁). Homing pigeons are trained to fly home, sometimes crossing hundreds of miles of unfamiliar area. At the same time, farm animals share similar characters with their dog partners. Horses, like dogs, perform complex tasks. And cats? They have more in common with dogs than one might think. Still it is much easier to show intelligence in dogs because they like to be trained. Dogs are not smarter than they are supposed to be, given what they are.