Reading Comprehension – In the late 1960s, while studying the northern-elephant


Slot – 1 – RC



In the late 1960s, while studying the northern-elephant-seal population along the coasts of Mexico and California, Burney Le Boeuf and his colleagues couldn’t help but notice that the threat calls of males at some sites sounded different from those of males at other sites. . . .

That was the first time dialects were documented in a nonhuman mammal. . . .

All the northern elephant seals that exist today are descendants of the small herd that survived on Isla Guadalupe . As that tiny population grew, northern elephant seals started to recolonize former breeding locations. It was precisely on the more recently colonized islands where Le Boeuf found that the tempos of the male vocal displays showed stronger differences to the ones from Isla Guadalupe, the founder colony.

In order to test the reliability of these dialects over time, Le Boeuf and other researchers visited Año Nuevo Island in California—the island where males showed the slowest pulse rates in their calls—every winter from 1968 to 1972. “What we found is that the pulse rate increased, but it still remained relatively slow compared to the other colonies we had measured in the past” Le Boeuf told me.

At the individual level, the pulse of the calls stayed the same: A male would maintain his vocal signature throughout his lifetime. But the average pulse rate was changing. Immigration could have been responsible for this increase, as in the early 1970s, 43 percent of the males on Año Nuevo had come from southern rookeries that had a faster pulse rate. This led Le Boeuf and his collaborator, Lewis Petrinovich, to deduce that the dialects were, perhaps, a result of isolation over time, after the breeding sites had been recolonized. For instance, the first settlers of Año Nuevo could have had, by chance, calls with low pulse rates. At other sites, where the scientists found faster pulse rates, the opposite would have happened—seals with faster rates would have happened to arrive first.

As the population continued to expand and the islands kept on receiving immigrants from the original population, the calls in all locations would have eventually regressed to the average pulse rate of the founder colony. In the decades that followed, scientists noticed that the geographical variations reported in 1969 were not obvious anymore. In the early 2010s, while studying northern elephant seals on Año Nuevo Island, [researcher Caroline] Casey noticed, too, that what Le Boeuf had heard decades ago was not what she heard now …..By performing more sophisticated statistical analyses on both sets of data, [Casey and Le Boeuf] confirmed that dialects existed back then but had vanished. Yet there are other differences between the males from the late 1960s and their great-great-grandsons: Modern males exhibit more individual diversity, and their calls are more complex. While 50 years ago the drumming pattern was quite simple and the dialects denoted just a change in tempo, Casey explained, the calls recorded today have more complex structures, sometimes featuring doublets or triplets. . . .

Q.1 From the passage it can be inferred that the call pulse rate of male northern elephant seals in the southern rookeries was faster because:?
  1. The male northern elephant seals of Isla Guadalupe with faster call pulse rates might have been the original settlers of the southern rookeries.
  2. The calls of male northern elephant seals in the southern rookeries have more sophisticated structures, containing doublets and triplets.
  3. A large number of male northern elephant seals from Año Nuevo Island might have migrated to the southern rookeries to recolonise them.
  4. A large number of male northern elephant seals migrated from the southern rookeries to Año Nuevo Island in the early 1970s.
Answer: 1

Q.2 Which one of the following best sums up the overall history of transformation of male northern elephant seal calls?
  1. Owing to migrations in the aftermath of near species extinction, the calls have transformed from exhibiting complex composition, less individual variety, and great regional variety to simple composition, less individual variety, and great regional variety.
  2. Owing to migrations in the aftermath of near species extinction, the average call pulse rates in the recolonised breeding locations exhibited a gradual increase until they matched the tempo at the founding colony.
  3. The calls have transformed from exhibiting simple composition, less individual variety, and great regional variety to complex composition, great individual variety, and less regional variety.
  4. The calls have transformed from exhibiting simple composition, great individual variety, and less regional variety to complex composition, less individual variety, and great regional variety.
Answer: 3

Q.3 Which one of the following conditions, if true, could have ensured that male northern elephant seal dialects did not disappear?
  1. The call tempo of individual male seals in host colonies changed to match the average call tempo of immigrant male seals
  2. Besides Isla Guadalupe, there was one more surviving colony with the same average male call tempo from which no migration took place.
  3. The call tempo of individual immigrant male seals changed to match the average tempo of resident male seals in the host colony.
  4. Besides Isla Guadalupe, there was one more founder colony with the same average male call tempo from which male seals migrated to various other colonies.
Answer: 3

Q.4 All of the following can be inferred from Le Boeuf’s study as described in the passage EXCEPT that:
  1. changes in population and migration had no effect on the call pulse rate of individual male northern elephant seals.
  2. male northern elephant seals might not have exhibited dialects had they not become nearly extinct in the nineteenth century
  3. the influx of new northern elephant seals into Año Nuevo Island would have soon made the call pulse rate of its male seals exceed that of those at Isla Guadalupe.
  4. . the average call pulse rate of male northern elephant seals at Año Nuevo Island increased from the early 1970s till the disappearance of dialects.
Answer: 3

Solutions:
Q.1 Refer to the following extract, “At other sites, where the scientists found faster pulse rates, the opposite would have happened—seals with faster rates would have happened to arrive first.” (from Isla Guadalupe). This extracts tell us that the original or first settlers might have been the seals from Isla Guadalupe with faster call pulse rates. This explanation points to option 1 as being the correct answer.

Option 2 is incorrect. The calls of male northern elephant seals having more sophisticated structures, containing doublets and triplets was found to be true throughout the population and not just in the southern rookeries. Secondly, this took place later in 2010 and not in the 1970s by which time there were no differences in call pulse rates in the entire seal population.

Option 3 contradicts the passage. The seals in Ano Nuevo had the slowest call pulse rates, not faster pulse rates. Therefore, had they migrated to the southern rookeries, the average pulse rates there would have decreased.

Option 4 does not answer the question asked. The question asked is of faster call pulse rates among male seals in the southern rookeries and not that of Ano Nuevo island. Hence, the correct answer is option 1.

Q.2 Refer to the two extracts, “Modern males exhibit more individual diversity, and their calls are more complex. While 50 years ago the drumming pattern was quite simple and the dialects denoted just a change in tempo, Casey explained, the calls recorded today have more complex structures, sometimes featuring doublets or triplets. . . “ and “In the decades that followed, scientists noticed that the geographical variations reported in 1969 were not obvious anymore…” From these extracts it can be inferred that the calls which had simple composition, less individual variety and great regional variety in the 1970s changed to complex compositions, great individual variety and less regional variety later. This explanation points to option 3 as being the correct answer.

Options 1, 2 and 4 can thus be eliminated.

Hence, the correct answer is option 3.

Q.3 The passage states that that the call tempo of individual immigrant male seals altered the average call tempo of resident male seals in a particular colony. If the call tempo of individual immigrant male seals changed to match the average tempo of resident male seals in the host colony then the call tempo average for that site would have been maintained and this call tempo rate would have been different from other call tempo rates in other sites (as was the case in 1969). This explanation points to option 3 as being the correct answer.

Option 1 directly contradicts the explanation above. It can be eliminated.

Options 2 and 4 would have made no difference to individual dialects as the crux of dialect variation was due to the call tempo of individual immigrant male seals changing to match the average tempo of resident male seals in the host colony.

Hence, the correct answer is option 3.

Q.4 Option 1 can be inferred from Le Boeuf’s study. Refer to the following extract, ‘“What we found is that the pulse rate increased, but it still remained relatively slow compared to the other colonies we had measured in the past” Le Boeuf told me. At the individual level, the pulse of the calls stayed the same: A male would maintain his vocal signature throughout his lifetime.’

Option 2 too can be inferred. Male northern elephant seals exhibited dialects after re-colonization of former sites after becoming nearly extinct and due to their isolation from each other. Had they not become extinct they would probably have had the same pulse rate. Option 4 can also be inferred. Refer to the following extract, “But the average pulse rate was changing. Immigration could have been responsible for this increase, as in the early 1970s, 43 percent of the males on Año Nuevo had come from southern rookeries that had a faster pulse rate.”

Option 3 cannot be inferred from Le Boeuf’s study. We cannot state with any degree of certainty that the influx of new seals into Ano Nuevo island would have made the call pulse rate of its male seals exceed that of those at Isla Guadalupe. The passage does not give us sufficient information to be able to make this inference.

Hence, the correct answer is option 3.


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