Most of the 500 whales stranded (搁浅)off Tasmania have now died. Dozens more stricken whales have been found in Australia’s largest ever mass stranding.The estimated total now stands at around 500, with the majority of that number dead and a tenth rescued by authorities on the Island state of Tasmania. Experts believe all of the animals would have been part of one large group. Officials began working to rescue survivors among an estimated 270 whales found on Monday on a beach and two sandbars near the remote coastal town of Strahan. Then another 200 whales were spotted from a helicopter on Wednesday less than 10 kilometres (six miles) to the south.All 200 had been confirmed dead by late afternoon. They were among the 380 whales that have died overall, with estimates from earlier today suggesting that 30 that were alive but stranded and 50 had been rescued since Tuesday, Mr Deka, Wildlife Service manager explained. He added,“We’ll continue to work to free as many of the animals as we can.We’ll continue working as long as there are live animals.”

It is not known what caused the animals to run aground. While stranding events are not unheard of, they are very rare in such large numbers. About 30 whales in the original stranding were moved from the sandbars to open ocean on Tuesday, but several got stranded again. About a third of the first group had died by Monday evening.

Australia’s largest mass stranding had previously been 320 pilot whales near the Western Australian town of Dunsborough in 1996.This week’s incident is the first involving more than 500 whales in Tasmania since 2009.Marine Conservation Programme wildlife biologist Kris Carlyon said the latest mass stranding was the biggest in Australia in terms of numbers stranded and died.

Marine scientist Vanessa Pirotta said there were a number of potential reasons why whales might become beached, including navigational errors.She explained, “They do have a very strong social system; these animals are closely bonded and that’s why we have seen so many in this case unfortunately in this situation.Rescuing them does not always work, because they are wanting to return back to the group, they might hear the sounds that the others are making, or they’re just disoriented and, in this case, extremely stressed, and just probably so exhausted that they in some cases don’t know where they are.” she added.

As the species migrates (迁徙) from Central Asia to Southeast Asia every autumn, it must cross over the Himalayan range. These mountains force the bar-headed goose to fly at around 30,000 feet above sea level, which is the highest altitude for migratory birds.

These geese have special adaptions that allow them to survive at the altitude. For example, a special protein (蛋白质) in blood cells that transports oxygen throughout the body allows their blood cells to combine with oxygen. Their circulatory system provides a constant supply of fresh, oxygenated blood to their wing muscles (肌肉). They have much larger lungs than other birds, which give them the ability to take in more air.

Scientists initially believe that the geese flow at an extremely high altitude for the full length of their migration. But later the data suggests that the birds use a much more effective way of travel. Instead of remaining at an extremely high altitude to fly over the mountain range, the geese hug the mountains, flying up and down depending on the obstacles (障碍物) in their way. This works better for them because they don’t have to use all their energy flying in an area with low oxygen; they can spend time flying at lower altitudes.

The geese also make use of nature to make this work easier. To fly down, they simply allow gravity to pull them. To fly back up, they make use of orographic (地形的) lift, which happens when flowing air meets an obstacle, such as a mountain. The mountain forces the air up, creating an upward draft. The birds take advantage of this draft, expending less of their own energy to fly up the mountain.

The way these birds have adapted to flying across the Asian continent during their annual migration is certainly an amazing way to see nature at work.

Scientists say they have found out a chemical produced by locusts（蝗虫）that causes the insects to join together in huge swarms（群）.

On their own, locusts are mostly harmless. But in large swarms, they can be extremely destructive. The new finding could lead to new methods to prevent locusts from joining swarms to destroy huge areas of crops.

A recent study published in Nature identifies a pheromone believed to be responsible for the insect’s swarming behavior. A pheromone is a chemical item produced by an animal that influences the behavior of another animal of the same kind.

The pheromone, known as 4VA, was found in the world’s most widespread kind of locust, the migratory locust. It powerfully drew locusts of both sexes and all ages, the research found. And it was produced when as few as four to five locusts came together.

Lead researcher Le Kang is with the Chinese Academy of Sciences’ Institute of Zoology. He told Reuters news agency that migratory locusts are so widespread and dangerous, they represent"a serious threat to agriculture worldwide. " Kang said further research will be needed to find out if 4VA exists in other species, such as the desert locust.

Kang said a chemical could be developed to block 4VA’s effects to prevent swarming. A man-made version of the pheromone might also be developed to attract locusts into traps to be killed. Locusts could also be developed with genetic changes that would not react to 4VA, Kang added. Such locusts could be sent to the wild to build wild non-swarming populations.

Leslie Vosshall, head of Rockefeller University’s Laboratory of Neurogenetics and Behavior in New York, said one of the most exciting developments would be finding a chemical that could block the reception of 4VA. She noted that there are still several unknowns about the research. These include whether 4VA is the only cause of swarm formation, and whether other locust species respond similarly to the chemical.