IELTS Reading 147: Tracking the Ocean's Long-Distance Travellers

Adapted from OCEARCH / Wildlife Conservation Society / Nature (Jorgensen et al.). IELTS Reading Section 3 difficulty, approximately 1,050 words. Source: https://www.ocearch.org/research/global-white-shark-project/

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Reading Passage

A. For centuries the great white shark was known mainly from what fishermen and sailors saw near the shore — a creature of the surface, glimpsed briefly and usually feared. Because these animals swim fast, dive deep and range across entire oceans, observing them in the open sea is enormously difficult, and for most of history almost nothing was known of where they went between those coastal encounters. That picture has changed dramatically in the last two decades, thanks to a small electronic device clamped onto an animal's dorsal fin. The technology has not merely added detail to old maps; it has overturned them, revealing migrations longer than anyone had guessed and hidden meeting places thousands of kilometres from land. Researchers now speak of replacing fear with facts, and the facts have turned out to matter not only for science but for conservation, because a shark that crosses oceans cannot be protected by a single marine reserve drawn around one beach. Old estimates of numbers, based on the few animals seen near shore, were wildly uncertain; the tags did what fieldwork never could, by following the animals themselves rather than waiting for them to appear.

B. The instrument behind the revolution is the pop-up satellite archival tag. Clamped to a shark's fin or back, it records, every few minutes, the depth the animal swims at, the surrounding water temperature, and the level of sunlight. Crucially, the tag is not meant to stay on forever. After a pre-set period it detaches itself, floats to the surface, and radios its stored data up to an overhead satellite. From the sunlight measurements scientists can estimate roughly where the shark was, using the length of the day and the timing of local noon. The method is indirect and not as precise as a phone's global-positioning signal, but it works on animals that cannot carry receivers and that spend most of their lives far from any coast. Deployed across many individuals and hundreds of cumulative days at sea, the fragments have been stitched into surprisingly complete journeys. Each tag costs enough that researchers cannot place one on every animal, but even a few hundred attachments, gathered over many years, reveal patterns that no amount of shoreline observation could. The tags also record the depth and temperature of every dive, so that the reconstructed journey is not a line on a map alone but a record of the underwater landscape the shark actually inhabits.

C. The first journey that astonished everyone belonged to a female named Nicole. Roughly 3.8 metres long, she was fitted with a tag off the coast of South Africa by a research team from the Wildlife Conservation Society. The team expected to learn something about her local movements. Ninety-nine days later, the tag popped to the surface not nearby, or even anywhere in southern African waters, but off the coast of Western Australia — on the opposite side of the Indian Ocean. In less than three and a half months, Nicole had swum thousands of kilometres straight across open water. The discovery settled an old argument: white sharks were not merely coastal predators tied to one hunting ground, but capable of — and apparently devoted to — transoceanic travel. Remarkably, Nicole later returned to South Africa, suggesting the crossing was not a random drift but a purposeful, repeated commute. Such long, directed trips implied that the animals navigate the vast, featureless ocean by mechanisms scientists are still trying to understand. Candidates include sensitivity to the Earth's magnetic field, navigation by smell, or some internal map built from years of memory; the tags have proved the journeys happen but have not, yet, shown how they are achieved.

D. Pacific sharks turned out to keep a secret of their own. Individuals tagged off central California vanish from the coast every year, and until the 2000s no one could say where they went. The satellite tags supplied the answer. They head west for about 2,500 kilometres into the open Pacific to a featureless, mid-ocean region researchers call the White Shark Cafe. There, far from any coastline, they spend several months making repeated deep dives into dark water to feed on squid and other small prey that live at depth, before returning to the continental shelf to hunt seals. The discovery was doubly important. It showed that a species everyone associated with beaches and seal colonies actually lives for much of its life in the deep ocean. And it identified a specific, shared gathering point — a place that, despite being thousands of kilometres from land, the sharks return to as reliably as migrants returning to a single field. That a dozen animals, tagged in different years, should all converge on the same blank patch of open sea argues that the spot offers something the sharks cannot find anywhere else.

E. These maps carry a clear message for those who would protect the species. White sharks are organised into perhaps nine recognisable populations around the world, each with its own routes, breeding areas and seasonal hotspots. Conservation that guards only the coastal sites where sharks come close to humans therefore protects just a fraction of their lives. A shark's real range includes offshore dining grounds, deep-water feeding zones and the long corridors it swims between them — routes that may cross the waters of several countries or the high seas beyond any nation's control. Tracking programmes now publish these journeys on open online maps, so that fishermen, planners and the public can see exactly which underwater highways matter. The hope is that protection will follow the animal itself, extending beyond the beaches where it is most visible to the invisible, ocean-spanning life that a tag on a fin has finally begun to reveal. The animals that sailors once imagined as mindless wanderers turn out to follow ancient, repeatable routes; the conservation task is simply to catch up with what they have known all along.

Questions 1-4

Choose the correct heading for paragraphs B, C, D and E from the list of headings below.

List of Headings i. How the pop-up tag works ii. The Pacific sharks' hidden offshore meeting place iii. Why one famous transoceanic trip was a shock iv. What the maps mean for conservation v. How sharks navigate using the stars vi. Why white sharks attack humans vii. The design of modern fishing nets

1. Paragraph B: ____
2. Paragraph C: ____
3. Paragraph D: ____
4. Paragraph E: ____

Questions 5-8

Choose the correct letter, A, B, C or D.

5. What does a pop-up satellite archival tag record? A. The shark's exact position via GPS at all times. B. Depth, water temperature and light level over a set period. C. The shark's body weight daily. D. Only the direction the shark is facing.

6. Why was Nicole's journey surprising? A. She swam from South Africa to Australia in 99 days. B. She stopped eating during the voyage. C. She was smaller than expected. D. She swam only at night.

7. What is the "White Shark Cafe"? A. A coastal seal colony in California. B. A mid-Pacific offshore area where sharks dive deep to feed. C. A breeding beach in Australia. D. An aquarium in South Africa.

8. According to the writer, why is protecting coastal sites insufficient? A. Sharks never return to coasts. B. Sharks spend much of their lives in offshore zones and corridors. C. Coastal reserves are too expensive to maintain. D. Sharks prefer warm freshwater rivers.

Questions 9-13

Do the following statements agree with the claims of the writer?

Write:

• TRUE if the statement agrees with the information
• FALSE if the statement contradicts the information
• NOT GIVEN if there is no information on this

9. Pop-up tags transmit their data to a satellite after detaching.
10. Nicole was tagged off the coast of Western Australia.
11. Pacific white sharks migrate to an offshore region about 2,500 km from land.
12. Scientists fully understand exactly how sharks navigate across open ocean.
13. White sharks are currently found in only two oceans worldwide.

Questions 14-15

Complete the summary below using NO MORE THAN TWO WORDS from the passage.

The tag estimates position from sunlight, using the length of the (14) _____________ and the timing of local (15) _____________.

Answers & Explanations

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