VOICE ONE:This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty.VOICE TWO:And I'm Shirley Griffith. This week, we tell about a discovery of gorillas in the Republic of Congo and the loss of Bengal tigers in Nepal. We also tell about a famous heart surgeon and what you need to know about your heart.(MUSIC)VOICE ONE:Deep in the forests in the northern part of the Republic of Congo, scientists have made a surprising discovery. Researchers discovered more than one hundred twenty-five thousand critically endangered western lowland gorillas.In the nineteen eighties, scientists estimated that the total population of western lowland gorillas in Central Africa was fewer than one hundred thousand. Since then however, the scientists believed this number had been reduced by at least half. They thought the animals were being killed off by hunters and disease, especially the deadly Ebola virus.VOICE TWO:The new population count was the result of intensive work by the Wildlife Conservation Society, based in New York City, and scientists of the Republic of Congo. They searched rainforests and swamps, looking for gorilla nests.Gorillas build beds, or nests, for sleeping each night. They use leaves and other parts of trees. The researchers use the number of nests they find to help estimate the local gorilla population. They found some forests had population densities that were among the highest ever recorded. The researchers studied an area of forty-seven thousand square kilometers. They announced the results of their population count at a meeting of the International Primatological Society Congress in Edinburgh, Scotland.VOICE ONE:The scientists say the higher number of gorillas is the result of efforts by the Republic of Congo to take care of its protected areas. The gorillas have also done well because they live in areas far away from people. And they have plenty to eat. Wildlife Conservation Society President Steven Sanderson said the success of the gorillas is proof that humans can help protect animal species in danger of disappearing.Western lowland gorillas are one of four recognized gorilla subspecies. Other subspecies include mountain gorillas, eastern lowland gorillas, and Cross River gorillas. The International Union for Conservation of Nature considers all of the subspecies to be critically endangered, except for the eastern lowland gorillas. That subspecies is considered endangered.Researchers at the meeting in Scotland warned about the dangers that continue to threaten gorillas. They say almost fifty percent of the world's species of primates are in danger of disappearing, especially in Asia. This is because the areas in which they live are being destroyed. And many animals are illegally hunted as food.(MUSIC)VOICE TWO:That was some good news about gorillas. But we have some bad news about tigers. Three years ago, between twenty and fifty Bengal tigers lived in the Suklaphanta Wildlife Reserve in Nepal. But this year, researchers reported evidence of only six to fourteen tigers. The Nepalese government announced the decrease of the tiger population last month. The wildlife reserve measures about thirty thousand hectares. It is the world's third largest living area for the big cats.VOICE ONE:Nepalese national parks and conservation officials called the situation very serious. They said illegal hunting is the major cause of tigers disappearing from this protected area.The World Wildlife Fund did most of the study about the tigers. The findings were based on pictures taken by camera traps from January to April. The camera traps contain devices that take a picture when they sense movement in the forest. Researchers used two cameras to take pictures of the tigers from both sides. But the cameras also photographed the hunters who killed the tigers and removed their remains.VOICE TWO:The Suklaphanta Wildlife Reserve is on the border with India. World Wildlife Fund officials say this makes it easy to illegally transport protected wildlife. Very little of the tigers' remains are found because all of the animal's parts are valuable in the illegal wildlife trade.Jon Miceler heads the World Wildlife Fund's Eastern Himalayas Program. Mister Miceler said that in May, two tiger skins were seized from the Nepalese border town of Dhangadi. So were thirty-two kilograms of tiger bones.VOICE ONE:Mister Miceler says the loss of tigers is linked to a powerful international criminal group that controls the illegal wildlife trade. Only about two thousand to four thousand Bengal tigers survive in the wild.Most live in forests in central and south India, Bhutan, and the Himalayan foothills of India and Nepal. Bengal tigers also live in China, Bangladesh and Burma. The World Wildlife Fund says populations of all kinds of tigers have decreased by ninety-five percent over the past one hundred years. And three kinds of tigers have disappeared.(MUSIC)VOICE TWO:Famous American heart surgeon Michael DeBakey died last month. He was ninety-nine years old. He performed more than sixty thousand operations during his long career. As a medical student in nineteen thirty-one, he invented the roller pump. Years later doctors used it for blood transfusions during heart operations. The roller pump became a major part of the heart-lung machine. The machine pumps oxygen-rich blood to the brain and other organs so doctors can operate on the heart.Michael DeBakey was a pioneer of open-heart surgery. The name means that doctors open the chest and perform surgery on the heart. Doctors may or may not open the heart as well.VOICE ONE:Doctor DeBakey developed a way to replace or repair blood vessels with Dacron, a stretchy manmade material. He continued to improve on the process. Today the DeBakey artificial graft is used around the world. He was also a pioneer in artificial hearts, heart transplants and recording surgeries on film. During World War Two in the nineteen forties, he helped develop the Mobile Army Surgical Hospital, or MASH.Michael DeBakey saved many lives during his long career as a heart surgeon. One life he helped save was his own. Two years ago he had a damaged aorta, which carries blood from the heart to the body. Surgeons repaired it with an operation he developed long ago.(MUSIC)VOICE TWO:Speaking of hearts, here is some information about that complex organ and how to keep it healthy. The heart has four parts. As the heart beats, it pumps blood through these chambers and the blood vessels in the body. The body is estimated to have at least ninety-six thousand kilometers of blood vessels. That is about the same as two and a half times around the Earth. But blood goes the distance in about twenty seconds on its way back to the heart. Each day the heart pumps about eight thousand liters of blood.The blood feeds the brain and other organs with oxygen and nutrients. It also carries away carbon dioxide and other waste. The heart pumps by expanding and contracting of muscle. In a healthy adult, the heart beats an average of seventy-two times a minute -- about one hundred thousand times a day.VOICE ONE:Rates of heart disease started growing sharply in the second half of the twentieth century. As machines did more and more work, people did less and less. Not only did physical activity decrease, but people started eating more processed foods.Experts say a diet low in fats and high in fruits, vegetables, proteins and whole grains may help reduce the risk of heart disease. At least thirty minutes a day of physical activity, enough to work up a sweat, can also help. A good night's sleep is also important for good health.Cardiovascular disease is caused by disorders of the heart and blood vessels. It includes heart attacks, strokes and high blood pressure. The World Health Organization says there are three major causes of cardiovascular disease: tobacco use, physical inactivity and an unhealthy diet. The W.H.O. says cardiovascular disease is the world's leading cause of death.(MUSIC)VOICE TWO:This SCIENCE IN THE NEWS program was written by Jerilyn Watson, Caty Weaver and Brianna Blake, who also was our producer. I'm Shirley Griffith.VOICE ONE:And I'm Bob Doughty. You can read and listen to our programs at 51voa.com. Join us next week for more news about science in VOA Special English.