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RC Passage
Direction for the questions 15 to 18: The passage below is accompanied by a set of four questions. Choose the best answer to each question.
In the late 1960s, while studying the northern-elephant-seal population along the coasts of Mexico and California, Burney Le Boeuf and his colleagues couldnāt 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 [after the near extinction of the species in the nineteenth century]. 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 AƱo Nuevo Island in Californiaāthe island where males showed the slowest pulse rates in their callsāevery winter from 1968 to 1972. āWhat we found is that the pulse rate increased, but it still remained relatively slow compared to the other colonies we had measured in the pastā 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 AƱo 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 AƱo 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 happenedāseals 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 AƱo 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.
RC Line-wise Explanation
Paragraph 1
"In the late 1960s, while studying the northern-elephant-seal population along the coasts of Mexico and California, Burney Le Boeuf and his colleagues couldnāt help but notice that the threat calls of males at some sites sounded different from those of males at other sites..."
Explanation: During the 1960s, researchers noticed that male elephant seals at different locations had unique vocal threat calls.
"That was the first time dialects were documented in a nonhuman mammal."
Explanation: This observation marked the first known case of vocal dialects in a nonhuman species.
Paragraph 2
"All the northern elephant seals that exist today are descendants of the small herd that survived on Isla Guadalupe [after the near extinction of the species in the nineteenth century]."
Explanation: Modern elephant seals all descend from a tiny group that survived near extinction on Isla Guadalupe.
"As that tiny population grew, northern elephant seals started to recolonize former breeding locations."
Explanation: Once the population recovered, the seals spread back to their old breeding sites.
"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."
Explanation: Le Boeuf found that seals in newer colonies had calls that were more different from those in the original colony, especially in tempo.
Paragraph 3
"In order to test the reliability of these dialects over time, Le Boeuf and other researchers visited AƱo Nuevo Island in Californiaāthe island where males showed the slowest pulse rates in their callsāevery winter from 1968 to 1972."
Explanation: To study if these vocal differences stayed consistent, researchers observed seals on AƱo Nuevo Island (where calls were slowest) over five winters.
"āWhat we found is that the pulse rate increased, but it still remained relatively slow compared to the other colonies we had measured in the pastā Le Boeuf told me."
Explanation: They discovered that the calls became slightly faster over time, but still slower than those from other colonies.
Paragraph 4
"At the individual level, the pulse of the calls stayed the same: A male would maintain his vocal signature throughout his lifetime."
Explanation: Each seal kept the same call tempo for life.
"But the average pulse rate was changing."
Explanation: However, the overall call tempo in the colony gradually changed.
"Immigration could have been responsible for this increase, as in the early 1970s, 43 percent of the males on AƱo Nuevo had come from southern rookeries that had a faster pulse rate."
Explanation: This shift may have been caused by new seals joining the colony from southern areas where the pulse rate was naturally faster.
"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."
Explanation: They hypothesized that these vocal differences had developed due to geographical isolation after recolonization.
"For instance, the first settlers of AƱo Nuevo could have had, by chance, calls with low pulse rates."
Explanation: The first male seals to settle in AƱo Nuevo may have happened to have slow calls.
"At other sites, where the scientists found faster pulse rates, the opposite would have happenedāseals with faster rates would have happened to arrive first."
Explanation: In contrast, colonies with fast-tempo calls likely began with seals that naturally had faster vocal rhythms.
Paragraph 5
"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."
Explanation: As more seals moved between colonies, the vocal differences began to average out, returning to the founder colonyās norm.
"In the decades that followed, scientists noticed that the geographical variations reported in 1969 were not obvious anymore."
Explanation: Over time, researchers observed that those distinct dialects were no longer clearly present.
Paragraph 6
"In the early 2010s, while studying northern elephant seals on AƱo Nuevo Island, [researcher Caroline] Casey noticed, too, that what Le Boeuf had heard decades ago was not what she heard now."
Explanation: In the 2010s, Caroline Casey also found that the earlier dialects described by Le Boeuf had disappeared.
"By performing more sophisticated statistical analyses on both sets of data, [Casey and Le Boeuf] confirmed that dialects existed back then but had vanished."
Explanation: They used advanced data analysis to confirm that while dialects were present in the past, they no longer exist.
"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."
Explanation: Todayās male seals differ in other waysāthey have more varied and intricate vocalizations.
"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."
Explanation: Previously, calls were simple and mainly differed in speed, but now they have layered, complex patterns.
RC Paragraph Explanation
Paragraph 1 Summary
Researchers first noticed dialects in male elephant seal calls during the 1960s, marking a historic discovery of vocal variation in a nonhuman mammal.
Paragraph 2 Summary
All modern elephant seals descend from a small founder group on Isla Guadalupe, and the vocal differences seen in recolonized areas likely arose from random variations among early settlers.
Paragraph 3 Summary
Between 1968 and 1972, researchers monitored one colony and found that while individual calls stayed constant, the overall tempo increased slightly but remained distinct.
Paragraph 4 Summary
The shift in colony-wide call tempo was likely caused by immigrants from faster-calling colonies. Le Boeuf and Petrinovich theorized dialects developed due to isolation during recolonization.
Paragraph 5 Summary
As populations mixed, the vocal dialects began to fade, and by later decades, scientists could no longer detect clear geographical differences.
Paragraph 6 Summary
Caroline Caseyās 2010s research confirmed the past existence of dialects, now lost. However, modern males display more individual variation and use more complex vocal structures than before.
RC Quick Table Summary
| Paragraph Number | Main Idea |
|---|---|
| Paragraph 1 | Dialects in seal calls were first identified in the 1960s. |
| Paragraph 2 | Modern seals descend from one small group; dialects likely emerged by chance. |
| Paragraph 3 | Individual calls stayed the same, but colony call tempo slowly changed. |
| Paragraph 4 | Immigrants influenced vocal changes; dialects stemmed from recolonization. |
| Paragraph 5 | Dialects faded as population movement increased and calls averaged out. |
| Paragraph 6 | Dialects are gone, but calls now show more individual and structural variety. |
RC Questions
Ques 15.All of the following can be inferred from Le Boeufās study as described in the passage EXCEPT that:
Ques 16. Which one of the following conditions, if true, could have ensured that male northern elephant seal dialects did not disappear?
Ques 17. Which one of the following best sums up the overall history of transformation of male northern elephant seal calls?
Ques 18. From the passage it can be inferred that the call pulse rate of male northern elephant seals in the southern rookeries was faster because:
