Often we cannot be sure whether an animal is acting intelligently or insrinctively. When a dog hears a strange noise, it barks. This is instinct. It cannot stop itself from doing this. It does not really know why it is doing this. But supposing a noise is on fire and the dog barks outside its master's bedroom until he wakes up. Is the dog using its intelligence? Is it solving the problem by waking its master or is it simply barking instinctively because it is afraid? Often we cannot be sure.

Many animals, however, can be taught to solve problems, especially when they are given rewards. Rats have been taught to touch a key to get food Animals in circuses （马戏团）have been taught to do all sorts of tricks to amuse the audience. In all these cases we may say that an animal is using intelligence. It is saying, "If I do this, I will get a reward. Therefore. I will do it.'' This may be thought of as a                           low kind of intelligence.

Many early domestic (驯养的) dogs ate almost no meat. Dogs living around 3000 years ago in what is now Spain were instead fed cereals, such as millet (小米), by their owners.

Although the diet may reflect the fact that meat was relatively in lack among human societies at the time, feeding dogs with cereals could have been advantageous, says Silvia Albizuri at the University of Barcelona in Spain. It may have been a way to ensure the dogs had plenty of energy for the hard work of herding and guarding livestock (牧群), she says, particularly since these dogs “were not pets as we think of them nowadays”. Albizuri and her colleagues studied the remains of 36 dogs from Can Roqueta, an archaeological site near Barcelona. It lies on a plain near the coast and was inhabited from the Stone Age onwards. The dogs lived in the Bronze Age and Iron Age, between 1300 and 550 BC, and had been buried in pits. The researchers obtained protein from the dogs’ bones and focused on the carbon in the samples, which give an indication of what the animals ate.

The dogs’ diets differed considerably. While nine of them ate plenty of meat and 10 were omnivorous (杂食的), the rest ate mostly plants.

The finding adds to the evidence that many early domestic dogs ate little meat, says Albizuri. This trend is thought to have begun with the start of farming. “When human societies began to domesticate plants during the Neolithic period, hunting decreased and the human diet was based mainly on vegetables,” she says. “Dogs began to be fed on plants, mainly cereals.”

Asian short-clawed otters (水獭) can teach each other how to solve puzzles to get food, according to a new study that took place in England. The research also showed that these cute animals have a good long-term memory —they could remember how to solve the puzzles even after several months.

Scientists from University of Exeter observed groups of Asian short-clawed otters in different places. They gave each group a selection of transparent (透明的) containers with meatball treats inside. Each box could be opened by twisting or pulling a particular lid or handle.

To get the food, the otters had to solve the puzzle of how to open the containers. The otters had two attempts at the puzzle several months apart. The researchers found that if one otter cracked the puzzle, its closest friends quickly solved it, too. The findings provide evidence of “social learning”—animals can learn from each other.

The scientists also found that on average the otters solved puzzles 69% faster the second time. It means that they can remember the details of how each puzzle works. “Our study is the first to show evidence of social learning and long-term memory in Asian short-clawed otters, which may be good news in terms of their adaptability and future survival,” said Alex Saliveros, lead author of the Centre for Ecology and Conservation on Penryn Campus in Cornwall.

Saliveros says the findings are important, because Asian short-clawed otters are declining in the wild, partly due to overfishing and pollution affecting the crustaceans and small fish they feed on. The discovery that the otters are able to find food in new ways and to pass on that knowledge toothers could be significant to their long-term survival.