名稱：18 Porpoises
內(nèi)容簡(jiǎn)介：
新概念英語第四冊(cè)（英音）
[al:新概念英語（四）]
[ar:MP3 同步字幕版（英音）]
[ti:Porpoises]

[00:01.49]Lesson 18
[00:03.31]Porpoises
[00:10.62]What would you say is the main characteristic of porpoises?
[00:17.06]There has long been a superstition among mariners that porpoises will save drowning men by pushing them to the surface,
[00:25.54]or protect them from sharks by surrounding them in defensive formation.
[00:31.72]Marine Studio biologists have pointed out that, however intelligent they may be, it is probably a mistake to credit dolphins with any motive of life-saving.
[00:43.54]On the occasions when they have pushed to shore an unconscious human being they have much more likely done it out of curiosity or for sport,
[00:53.55]as in riding the bow waves of a ship.
[00:57.55]In 1928 some porpoises were photographed working like beavers to push ashore a waterlogged mattress.
[01:06.19]If, as has been reported, they have protected humans from sharks,
[01:11.15]it may have been because curiosity attracted them and because the scent of a possible meal attracted the sharks.
[01:18.95]Porpoises and sharks are natural enemies.
[01:22.48]It is possible that upon such an occasion a battle ensued, with the sharks being driven away or killed.
[01:31.19]Whether it be bird, fish or beast, the porpoise is intrigued with anything that is alive.
[01:38.09]They are constantly after the turtles, who peacefully submit to all sorts of indignities.
[01:44.87]One young calf especially enjoyed raising a turtle to the surface with his snout, and then shoving him across the tank like an aquaplane.
[01:54.64]Almost any day a young porpoises may be seen trying to turn a 300-pound sea turtle over by sticking his snout under the edge of his shell
[02:04.07]and pushing up for dear life.
[02:06.72]This is not easy, and may require two porpoises working together.
[02:12.26]In another game, as the turtle swims across the oceanarium, the first porpoise swoops down from above and butts his shell with his belly.
[02:22.62]This knocks the turtle down several feet.
[02:25.63]He no sooner recovers his equilibrium than the next porpoises comes along and hits him another crack.
[02:32.79]Eventually the turtle has been butted all the way down to the floor of the tank.
[02:38.16]He is now satisfied merely to try to stand up, but as soon as he does so a porpoise knocks him flat.
[02:46.00]The turtle at last gives up by pulling his feet under his shell and the game is over.