Table of Contents
BEST IELTS Academic Reading Test 537
IELTS ACADEMIC READING TEST 537 – PASSAGE – 3
IELTS ACADEMIC READING TEST – 537
READING PASSAGE – 3
Marine mammals exhibit their ingenuity
Dolphins use ‘tools’ to help hunt for food
1. In the deep, clear channels of Australia’s Shark Bay, bottlenose dolphins have discovered tools, raising questions about the origins of intelligent behavior, the nature of learning, and the birth of technology. There, dolphins in one extended family routinely use sponges* to protect their noses as they forage for fish hidden in the abrasive seafloor sand, according to Georgetown University scientists.
2. As far as the researchers can tell, a single dolphin may have invented the technique relatively recently and taught it to her offspring. The simple innovation dramatically changed their behavior, hunting habits and social life, the researchers found. Those who adopted it became loners who spend much more time hunting than others, and dive more deeply in search of prey. The sponging dolphins teach the technique to all their young, but only the females seem to grasp the idea.
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‘It is indisputably tool use,’ says primate anthropologist Craig Stanford at the University of Southern California, an authority on animal cognition and behavior. For those seeking a glimpse of our own beginnings, the dolphins of Shark Bay offer a hint of the inventive impulse that occurred when our earliest ancestors first shaped destiny by fashioning implements with their hands.
3. Tool use of any sort among wild animals is rare, difficult to document reliably, and controversial. The line between instinct, ingenuity and intelligence is easily blurred by wishful thinking, experts caution. Field observations often give rise to scholarly disputes. Even so, 10 primate species of monkeys and apes, along with 30 species of birds, are thought to use sticks, rocks or leaves as tools.
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4. In the first in-depth analysis of this natural dolphin behavior, marine biologist and psychologist Dr Janet Mann at Georgetown University and her colleagues found that the dolphins of Shark Bay use their makeshift hunting masks more often than any other species uses tools, except human beings.
5. The curious hunting habit was first observed by a local fisherman who reported to marine biologists that he had seen a dolphin with an odd growth on its nose. Monitoring its movements through the bay’s unusually clear waters, researchers soon discovered that the dolphin was actually balancing a conical basket sponge on its nose.
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6. At first, it was not evident what the dolphin was doing with a sponge. Observing from a small boat, Dr. Mann and her colleagues eventually identified 41 dolphins who regularly used sponges to hunt, cataloging 1,295 dives in which they surfaced with sponges on their snouts. Researchers were startled to realize that the dolphins of Shark Bay employed one living creature as a tool to help hunt another.
7. Not any basket sponge would do, the researchers soon learned. The dolphins might search for 10 minutes to locate one with the right conical shape to cap their nose, tear it free of its mooring, and then carry it to a preferred hunting ground along channels between eight meters and 13 meters deep. “You can see that they are scattering the sand gently as they go along,” says Dr. Mann. ‘When they startle a fish out of the sand they immediately drop the sponge and go after it.
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8. ‘They return to retrieve the sponge and pick up the hunt again, repeating the pattern. “They really use these sponges as a foraging tool,” says dolphin biologist Maddalena Bearzi, president of the Ocean Conservation Society of Los Angeles. ‘They discovered it could create an advantage in their foraging technique, and they pass it from generation to generation.’ However, among the hundreds of dolphins living in this bay, only a few dozen use sponges to keep from scraping their noses, and that offered researchers an opportunity to compare creatures that use tools to others of the same species that do not.
9. Although these dolphins all appear to be related, researchers at the University of New South Wales suggest that nurture, not nature, is the reason these dolphins use tools, ruling out genetic explanations for the behavior. Instead, they are convinced that the use of sponges is passed from one generation to the next through imitation. Among bottlenose dolphins, mothers nurse their young for up to eight years, ample time for calves to absorb their mother’s hunting tricks by observation. “This is an example of culture among these animals,” says Dr. Bearzi. This is part of the reason it is so important.’
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10. So far, almost all of the dolphin spongers have proven to be female. “The sex difference is really striking,” says Dr. Mann. ‘I don’t know of another species where it is so dramatic.’ Of the sponge offspring, only the daughters could be seen still sponging once they reached maturity. The sons tried it but almost always abandoned it. Male dolphins rarely play a role in child rearing and tend to fish in packs.
11. For Dr. Mann, the discovery that dolphins, too, are tool users adds an unexpected dimension to the history of innovation, shedding new light on animal intelligence. Clever mimics and fast learners, dolphins have unusually large brains – four times the size of a chimpanzee’s and second only to humans in relative size. ‘It speaks to this whole issue of creativity and learning and brain size,’ she says. The number one question that drives me and others is: Why do dolphins have such big brains? What are they doing down there in the water that requires them to be so smart?’
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Questions 27-30
Do the following statements agree with the claims of the writer in Reading Passage 3? In boxes 27-30 on your answer sheet, write:
YES if the statement agrees with the claims of the writer
NO if the statement contradicts the claims of the writer
NOT GIVEN if it is impossible to say what the writer thinks about this
27. Researchers believe that the use of sponges for hunting may have originated with one female dolphin’s experimentation.
28. Research into tool use by dolphins can help us understand the origins of the use of tools by humans.
29. There is general agreement among researchers on the relationship of tool use among animals and animal intelligence.
30. Dr. Mann’s analysis of dolphin behavior has been criticized by some other scientists.
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Questions 31-35
Choose the correct letter, A, B, C, or D.
31. Some bottlenose dolphins in Shark Bay use sponges
A. to attract fish.
B. to avoid getting hurt.
C. to supplement their diet.
D. as a form of decoration.
32. The use of sponges by bottlenose dolphins results in their
A. living longer.
B. attracting more mates.
C. becoming more isolated.
D. becoming more aggressive.
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33. The Shark Bay fisherman mentioned in the passage
A. provided an explanation for the dolphins’ hunting habits.
B. made numerous observations of the dolphins in Shark Bay.
C. notified the media about dolphins balancing sponges on their noses.
D. thought the sponge was permanently attached to the dolphin’s nose.
34. The dolphins sometimes take some time to find a sponge because
A. some sponges are too heavy.
B. sponges are quite rare in Shark Bay.
C. they are only satisfied with sponges that fit well.
D. they have individual preferences for types of sponges.
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35. The fact that only a few dozen Shark Bay dolphins use sponges in this way allowed researchers to
A. investigate different behaviors within one species.
B. track individual members of a species.
C. decides whether the behavior was tool use or not.
D. explain the purpose for the behavior.
Questions 36-40
Complete each sentence with the correct ending, AH, below. Write the correct letter, AH, in boxes 36-40 on your answer sheet.
36. A genetic explanation for the dolphins’ use of sponges
37. Observation of the behavior of their mothers
38. The continued use of sponges in adulthood
39. A tendency to hunt for fish in groups
40. The clever behavior of the dolphins
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A. is more frequent among female dolphins.
B. is possibly linked to a physical characteristic.
C. is only possible in salt water.
D. is more typical of male dolphins.
E. is evidence of a dolphin’s use of sound.
F. is a threat to commercial fishing.
G. is the most likely way that sponge use is learned.
H. is not accepted by investigators.
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ANSWERS
27. YES
28. YES
29. NO
30. NOT GIVEN
31. B
32. C
33. D
34. C
35. A
36. H
37. G
38. A
39. D
40. B
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