As a young man, Paul Beier hiked in the mountains of California. Since then, he has decided to choose his career as a wildlife protector. He went to school to learn more first of all. After he earned his doctor's degree, he eagerly signed up for a job studying cougars  , which once lived throughout the United States, but now live mainly in the Rocky Mountains and westward. They need not only a lot of land to survive but also plenty of food and places to raise their young. But many wild areas have been divided by freeways and taken over by towns. The small wilderness areas of the Santa Ana Mountains in Southern California didn't have much room for them. And yet a few still lived there. How did they do it? Many big animals are disappearing. Those that survive are being trapped in shrinking patches of habitat. A patch may not have enough space or food for a cougar to survive. Scientists wondered if cougars could move from one patch to another. If so, maybe humans could preserve wildlife corridors to connect the patches, providing enough room for the animals. But no one had shown that animals use wildlife corridors in real life. To see if cougars had found corridors through local suburbs and freeways, Paul and his research team studied 32 cougars for five years. They used a drug to make each cat sleep, buckled a radio collar around its neck, and let it go. Every day, Paul used an electrical device that sends and receives radio signals to find cougars, listening for radio beeps from their collars. Once or twice a week, he trailed one of the cougars all night. He traced their travels on a map. Sure enough, some of them had discovered paths from one small park land to the next. One cougar became famous for his travels. He was named M6:"M"for Male, and"6"because he was the sixth one collared in the study. M6's corner of the Santa Ana Mountains wasn't large enough for him. Chino Hills State Park was not far away, but the trip was not safe. After dark, M6 used a paved vehicle underground passage to cross undera busy eight-lane freeway. He slipped by a riding stable, and then picked his way through a golf course and across two sets of busy railroad tracks. Finally, he arrived in the sheltered canyons of 12,000-acre Chino Hills State Park. There, the cougar found deer to hunt. During a year and a half, the scientists recorded M6 making this journey 22 times! Then Paul learned of plans to build houses, gas stations, and a mall that would block M6's path. Paul once said,"The loss of this corridor would guarantee the extinction of the cougar from the Chino Hills and endanger the entire population of lions in the Santa Ana Mountains."A local citizens' group called Hills for Everyone raised money to buy the land and add it to the state park. When the group visited the state capital and showed the map that Paul had made of M6's journeys, the lawmakers saw how important the corridor was. The lawmakers had the passage preserved, with the pavement removed and with native bushes near the openings. While traffic roared above, M6 and other cougars could move safely between the state park and the mountains. Other animals such as deer, foxes, and bobcats could also use the corridor. Paul's research showed that wildlife corridors can save animals. Since his study in the Santa Ana Mountains, scientists around the world have begun restoring and protecting wildlife corridors. What had happened to cougars before Paul began to study them?
They had been driven away by humans. Their habitats had been becoming smaller. They had lived throughout the world. Their young had been hunted by humans.