SCIENCE IN THE NEWS #2097 - DigestBy StaffThis is Sarah Long.And this is Bob Doughty with SCIENCE IN THE NEWS, a VOA Special English program about recent developments in science. Today, we tell about how dolphins communicate. We tell about the thinning of the ice sheet in Greenland. We tell about a shorter treatment for pregnant women with the virus that causes AIDS. And we tell about the threat to the world's plants and animals.
A new study of bottlenose dolphins suggests that they may communicate even better than scientists thought earlier. Vincent Janik (YAH-nik) recorded the voices of twelve wild dolphins off the coast of Scotland. Mr. Janik is a biologist at the University of Saint Andrews in Britain. He also works at the Woods Hole Oceanographic Institution in the American state of Massachusetts. The journal Science published his findings. They represent a major gain toward understanding dolphin communication.
Mr. Janik says the animal can make exactly the same sound -- a whistle -- made by another dolphin. He found that a second dolphin could recognize this copy of its whistle. And he reports that the animal can repeat and return this same sound to the first dolphin.Such communication has been observed before. It happens when a captured dolphin lives with other captured dolphins. But Mr. Janik says this system of call and response has never before been observed in the wild. His study was possible because a dolphin can make a sound all its own. It is the only mammal besides a human known to do this. Some scientists believe dolphins use a form of language.Mr. Janik recorded almost five hours of dolphin sounds. The animals were in Moray Firth in Scotland, near Loch Ness. He found that a dolphin could copy the whistles of another dolphin even at a distance. For example, two dolphins exchanged whistles in less than one second. This happened when the two animals were more than five-hundred meters apart. Mr. Janik says this shows one dolphin can directly communicate with another dolphin.
Dolphins whistle by using tissue within their noses. The sounds come from the front of their heads. A dolphin makes other sounds besides whistles. It makes a sound like a sharp "click" to find distant objects. This click can reach very high-frequency levels. The dolphin also makes a noise similar to the barking of a seal.Scientists have believed for a long time that the bottlenose dolphin is very intelligent. A main reason is the size of its brain. The dolphin brain weighs about one-percent of its body weight. The brains of humans weigh about two-percent of their body weight.
Captured dolphins learn quickly. Many dolphins are trained to perform tricks in shows at water parks. For example, dolphins are taught to react to commands. They obey orders like "Catch the ball" or "Jump through the ring." The military of several nations also have trained dolphins to find underwater bombs placed on ships.
((MUSIC BRIDGE))The American space agency NASA says the ice that surrounds the world's largest island is getting thinner. NASA scientists say the ice in some coastal areas of Greenland is decreasing at a rate of more than one meter each year. The scientists note any change is important because a smaller ice sheet could result in higher sea levels.
Eighty-five percent of Greenland is covered with ice. In some areas, the ice is more than three kilometers thick. NASA scientists completed a map of Greenland's ice sheet a few months ago. The project took almost seven years to complete.
The scientists measured the ice sheet with laser equipment on airplanes. They also used information provided by Global Positioning Satellite receivers orbiting earth.NASA scientists say the mapping project shows changes in the height of the ice sheet for the first time. For example, it found that ice at the center of Greenland is becoming a little thicker.
However, project scientist Bill Krabill said the scientists found a loss of about fifty-one cubic kilometers of ice from the ice sheet each year. He says this would explain about seven percent of the observed increase in sea levels. Mr. Krabill says this amount of sea level rise does not threaten coastal areas.
Scientists say studying Greenland's ice sheet may be one of the best ways to measure changes in the climate in the northern part of the world.
((MUSIC BRIDGE))You are listening to the Special English program SCIENCE IN THE NEWS on VOA. This is Sarah Long with Bob Doughty in Washington.
Doctors say they can shorten the length of drug treatments for pregnant women who are infected with the virus that causes the disease AIDS. The drug treatments keep the mother from passing the virus to her unborn child. However, the drugs are very costly and many women in developing countries can not pay for them. Shortening the treatment periods could help solve this problem.
For years, industrial nations have treated H-I-V-infected pregnant women with the drug A-Z-T for periods of three to six months. This A-Z-T treatment has lowered the spread of H-I-V infection from mother to baby to about seven percent.Now, a team of French, Thai and American doctors has been studying shorter and less costly treatments. Marc Lallemant [LA-leh-MAHN] of the Research Development Institute in Paris led the study. He says his team has found success with treatments that costs hundreds of dollars less than those used in the United States and Europe.
The researchers say three short A-Z-T treatment plans provided new babies with H-I-V protection that is similar to the longer-term treatments. More than one-thousand-four-hundred women took part in the study in Chiang Mai, Thailand.
One group of women took A-Z-T for the last twelve weeks of their pregnancy. Another group took the drug for the last five weeks of pregnancy. Their new babies were given A-Z-T either for three days or for six weeks after birth. About seven percent of the babies got H-I-V when both mothers and babies received the longer treatment. However, the rate of infection was about the same in cases where either the mother or the baby got the longer treatment.
((MUSIC BRIDGE))The World Conservation Union says the world is facing an environmental crisis. It says more than eleven-thousand kinds of plants and animals are at risk of disappearing forever. And more than four-thousand species are close to being declared threatened.
The group released a report about the crisis recently. Its so-called Red List identifies those species that are in danger of being lost. The study examined eighteen-thousand organisms around the world. The group says human activity already has forced more than eight-hundred species to disappear in the past five-hundred years.
The World Conservation Union says the number of endangered species has increased since it published its last report four years ago. For example, the number of endangered monkeys and apes has risen fifty percent. The rise is mostly the result of the destruction of forests. Monkeys, apes and many other animals are also being killed for their meat.But environmentalists say the endangered species list is just the beginning. They note that there are millions of species yet to be discovered. And they say many of those may already be threatened.
The World Conservation Union says Indonesia, India, Brazil and China are among the countries with the most threatened animals and birds. It says plant species are decreasing quickly in South and Central America, Central and West Africa and Southeast Asia.
Experts say the destruction of forests and the environment is the biggest cause of species loss. And they say there is evidence of species loss because of dams and other changes to rivers.
This SCIENCE IN THE NEWS program was written by Jerilyn Watson, George Grow, Caty Weaver and Cynthia Kirk. It was produced by George Grow. This is Sarah Long.And this is Bob Doughty. Join us again next week for more news about science in Special English on the Voice of America.