Urban swans might be born with a daredevil gene that makes them less fearful of humans, compared with their rural colleagues.

A study has found swans living in cities tend to be bolder and it is at least partly determined by a gene called DRD4. Birds with this gene could therefore be better adapted to settling in more populated areas, while more timid（胆怯的）swans would escape to less inhabited regions.

It could help to explain why swans in public parks and on urban rivers have a reputation for being so aggressive towards humans - they are simply not afraid of us.

Biologists from some universities in Australia, tracked and collected blood samples from black swans living in two wetlands near cities. One group of swans lived in a recreational urban park, while the other occupied a waste-water processing site out of town. The two areas were less than 20 miles apart. Later, from 2011 through 2013, the researchers started systematically scaring the swans at both sites. The researchers approached the birds and calculated how close they could get before they flew away. As expected, they noticed that while rural swans started flying away if a human was closer than 119 meters, the scientists could come as close to urban swans as 39 meters before taking off.

Analyses of the blood samples, in fact, showed that 83 per cent of the less cautious swans presented the same genetic DRD4 variation（变异)while rural swans have different genetic makeups resulting in more wariness(谨慎，小心）.

The researchers conclude that swans with the bold variation of the gene might choose to live in urban environments, as they tend to be less bothered by human presence.

Dolphin （海豚） or not a dolphin? That is the question! You see, there are several types of dolphins. Some are saltwater dolphins while others are river dolphins.

"What are the 32 types of dolphins?" When people are asking the question, they are actually referring to the saltwater dolphins in oceans and seas. The river dolphins living in fresh water, are not   included   in   these   species   （ 物种）.   But what would   be   the   answer   in this   case   if   we   ask,

"Dolphin or not a dolphin?" The answer would obviously be yes. River dolphins still belong to the dolphin family.

Among the 32 types of dolphins, some do not actually wear the word "dolphin" in their names, such as the tucuxi, while others actually have the word "whale" as part of their names even if they are not whales but in fact, belong to the dolphin family, for example, the melon-headed whale and the killer whale. So what would be the answer to the question "dolphin or not a dolphin?" in these cases? It would be yes. All these species do belong to the dolphin family.

Another question that people ask is, "Are the sea animals that perform at aquariums （水族馆） all dolphins?" So, it always seems to come back to the question, "Dolphin or not a dolphin?" Well the answer is no in this case. The sea animals that perform there are not all dolphins. The beluga which people tend to think belong to the dolphin family because they show what seems like a smile, like most dolphins, are in fact a species of the whale family.

Now that you read these facts about dolphins, you probably realize that certain sea animals may appear to be part of the dolphin species and that others seem to be part of the whale family, but in either case, it is not obvious and can be surprising when you identify a sea animal as being a dolphin or not a dolphin. That is the question!

Known as “ships of the desert”, camels have long been used for transport across the sands. However, for people in the United Arab Emirates (阿拉伯联合酋长国), camels are also beauty pageant contestants (选美比赛选手).

They have strict criteria (标准) to judge a camel’s beauty, including the size of its head, the length of its neck and whether its mouth can cover its teeth. Not every camel is blessed with (赐予) pretty lips or a long neck, so locals have turned to cloning.

Reproductive Biotechnology Center in Dubai, UAE, is the only clone facility in the Gulf, according to CCTV. “We have so much demand for cloning camels that we are not able to keep up,” the center’s scientific director, Nisar Wani, told AFP.

“We are now producing plenty, maybe more than 10 to 20 babies every year. This year we had 28 pregnancies (怀孕) so far; last year, we had 20,” Wani said.

“Beauty queens” are the most popular order. Clients will pay between $54,500 to $109,000 (about 350,533 to 701,066 yuan) to duplicate (复制) a camel. “The price of the camel is determined according to its beauty, health and how well-known the breed (品种) is,” Saud al-Otaibi, who runs a camel auction (拍卖) in Kuwait, told AFP.

Beauty pageants are not the only driver of the camel cloning industry. Many customers want to reproduce camels that produce large amounts of milk. “We have cloned some camels that produce more than 35 liters of milk a day,” Wani told AFP. “Normal camels produce an average of 5 liters a day.”

On April 8, 2009, Dubai claimed the world’s first cloned camel, Injaz. From the minute Injaz was born, there was no going back.

The center is producing “racing champions, high milk-producing animals ... and winners of beauty contests”, added Wani.

Cloning animals comes with concerns. Some scientists worry that continued use of this technology could lead species to extinction via “genetic bottleneck (种群遗传瓶颈效应)”, which happens when species lack genetic diversity .Cloning is also costly and incredibly hard to get right–up to 90 percent of attempts to clone animals end in failure, according to Wired, a US magazine.