[ti:Scientists Get First-Ever Measure of Blue Whale Heart Rate] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]For the first time ever, scientists have recorded the heart rate [00:06.08]of the world's largest creature: the blue whale. [00:11.72]To get this reading, they attached an electrocardiogram device to the body of a whale. [00:21.04]They found that the mammal's heart rate can slow to just two beats a minute [00:28.52]as the animal searches for food below the surface of the ocean. [00:35.76]The highest heart rate they recorded was 37 beats a minute [00:41.27]after the whale returned to the surface for air. [00:47.12]The team's study appears online in the publication Proceedings of the National Academy of Sciences. [00:56.08]The blue whale is the largest animal that has ever lived. [01:01.52]It can grow to 30 meters long and weigh as much as 181,000 kilograms. [01:11.20]The animal's heart alone weighs more than a fully grown cow. [01:18.92]Stanford University ocean biologist Jeremy Goldbogen led the blue whale heart rate study. [01:28.20]He said such research helps scientists understand how massive animals operate. [01:37.60]Generally, larger animals have slower heart rates. [01:43.32]A normal human heart of a person at rest beats 60 to 100 times each minute. [01:52.80]It increases to about 200 beats a minute during exercise. [01:59.92]The smallest mammals, shrews, have heart rates of more than a thousand beats per minute. [02:08.36]The researchers recorded nine hours of information [02:12.92]on a 22-meter-long male from the Pacific Ocean off the coast of California. [02:21.52]The data did not come easily. [02:24.80]"First, we has to find a blue whale, which can be very difficult" Goldbogen said, [02:31.02]because these animals live across massive areas of open ocean. [02:37.88]But, with years of research experience and some luck, he explained, [02:43.56]the team was able to position a small boat along the whale's left side. [02:51.20]Then, the researchers connected a special recording device to a very long pole. [02:59.72]As the whale surfaced to breathe, they quickly deployed the device [03:05.06]as near to the animal's heart as possible: just behind its left flipper. [03:13.16]The small device had four suction cups on it, [03:17.28]permitting it to remain on the whale for several hours. [03:24.08]Blue whales belong to the baleen whale family. [03:28.46]These whales are toothless. [03:31.31]Instead of teeth, they have baleen, [03:35.40]a softer material made from the same substance as fingernails. [03:41.92]To feed, the whales flood their mouths with huge amounts of water [03:47.67]and then release it through the baleen. [03:51.85]It serves as a filter, trapping krill and other very small sea animals [03:59.02]that make up the baleen whale diet. [04:03.36]During feeding dives, the blue whale under observation [04:08.32]showed extremely low heart rates, usually of four to eight beats a minute [04:15.13]and as low as two beats a minute. [04:19.56]After surfacing to breathe after food dives, [04:23.28]the whale had heart rates of 25 to 37 beats per minute. [04:30.92]Blue whales have fascinated biologists and people in general for years. [04:37.93]They are not only the largest and biggest-brained animals. [04:43.44]They are also the loudest. [04:46.48]They can communicate with other whales hundreds of miles away. [04:52.67]I'm Caty Weaver. [04:54.36]更多听力请访问51VOA.COM