英语听力：自然百科 白鲸

Meet Tiqa, the newest member of the beluga family at Vancouver Aquarium! The calf was born in June of last year. Tiqa spends her days training with the aquarium staff and swimming close to her mother Qila. In the wild, belugas live in Arctic and sub-arctic waters along the coasts of Alaska, Canada, Greenland, Norway and Russia. Biologists estimate there are about 100,000 Belugas in the wild. But although the number is greater than that of other whale species, beluga numbers have taken a battering after decades of over-hunting. As of the 2008, the beluga is listed as “near-threatened” by the International Union for Conservation of Nature. This is because ofuncertainty about the actual number of Belugas across its range, especially in the Russian Arctic. The IUCN claims that if current conservation efforts stopped, especially management of hunting, beluga population would likely qualify for “threatened” status within 5 years.

Vancouver Aquarium research associate, Valeria Vergara, watches and listens closely to the beluga whale family. She is studying how Tiqa , the beluga calf, is learning to communicate with her mother Qila and grandmother Aurora. What she discovers could offer important clues about how belugas live in the wild. Using sophisticated underwater listening devices, Vergara has classified 29 types of Beluga calls. Belugas rely on echolocation--their own built-in sonar systems and dozens of vocalization patterns to navigate and communicate.

"The echolocation system of these animals, belugas in particular, is incredibly complex or sophisticated. They navigate through sound. They map their entire surroundings. Through sonar they are able to navigate very, very precisely."

Trainers at the Vancouver Aquarium lead baby Tiqa , her mother Qila and grandmother Aurora through a daily training regiment. The belugas are never too shy to vocalize with the trainers and impress visitors with their movements and sounds. Global warming is creatingunprecedented pressures for beluga whales in Arctic and sub-Arctic waters.

"Right now, especially with the ice float , and all that are changing up there, that's basically saying okay, a boat traffic, come on and up, it's gonna be a lot easier to move back and forth. We start throwing a lot more noise up there and a lot more things that may impact how those animals are able to communicate with each other. We can see some big changes."