新概念英语听力mp3下载第四册lesson 18 Porpoises

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There has long been a superstition among mariners that porpoises will save
drowning men by pushing them to the surface, or protect them from sharks by
surrounding them in defensive f.mp3ation. 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. 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,as in riding the bow waves of a ship. In 1928 some porpoises
were photographed working like beavers to push ashore a waterlogged mattress.
If, as has been reported, they have protected humans from sharks, it may have
been because curiosity attracted them and because the scent of a possible meal
attracted the sharks. Porpoises and sharks are natural enemies. It is possible
that upon such an occasion a battle ensued, with the sharks being driven away
or killed.
Whether it be bird, fish or beast, the porpoise is intrigued with anything that
is alive. They are constantly after the turtles, the Ferdinands of marine life, who
peacefully submit to all sorts of indignities. One young calf especially enjoyed
raising a turtle to the surface with his snout and then shoving him across the
tank like an aquaplane. Almost any day a young porpoise may be seen trying
to turn a 300-pound sea turtle over by sticking his snout under the edge of his
shell and pushing up for dear life. This is not easy, and may require two porpoises
working together. In another game, as the turtle swims across the oceanarium,
the first porpoise swoops down from above and butts his shell with his belly.
This knocks the turtle down several feet. He no sooner recovers his equilibrium
than the next porpoise comes along and hits him another crack. Eventually the
turtle has been butted all the way down to the floor of the tank. He is now satisfied
merely to try to stand up, but as soon as he does so a porpoise knocks him
flat. The turtle at last gives up by pulling his feet under his shell and the game
is over.