Question 14·Medium·Central Ideas and Details
For centuries, shepherds in mountainous regions have relied on guardian dogs to protect livestock from predators. Ecologist Maria Dominguez recently conducted a study in the Pyrenees comparing flocks accompanied by dogs with those protected by high-tech deterrent lights. Over two years, illuminated pastures recorded slightly fewer predator visits, but Dominguez found that sheep tended to cluster near the bright devices, reducing grazing time and weight gain. By contrast, flocks guarded by dogs roamed widely and gained more weight, even though occasional wolf tracks were still found nearby.
Which choice best states the main idea of the text?
For main idea questions, first read the whole passage and briefly restate, in your own words, what the passage is mostly about and what overall conclusion it reaches. Then check each answer to see whether it (1) covers the entire passage rather than a single detail, (2) matches the author’s attitude and conclusion, and (3) avoids adding new information that isn’t in the text. Eliminate choices that are too narrow, focus on side details, or introduce unstated claims, and select the one that best summarizes the comparison or argument the passage makes.
Hints
Locate the comparison
Notice that the passage talks about two protection methods. Ask yourself: what is the author trying to show by comparing these two methods?
Focus on the conclusion, not just one detail
Look especially at the last few sentences of the passage. How does the information about sheep clustering near lights versus roaming with dogs help you understand the overall point?
Check which choice covers the whole passage
Which answer choice captures both predator encounters and the effects on sheep behavior and weight, instead of focusing only on predators or only on one side detail?
Watch for ideas not in the passage
Be careful with answers that introduce new claims, like long-term trends or causes (for example, what mostly determines weight gain) that the passage never directly discusses.
Step-by-step Explanation
Identify the general topic and focus
First, note what the passage is mainly about. The text discusses two different methods of protecting sheep from predators in the mountains: long-used guardian dogs and newer high-tech deterrent lights. The focus is on comparing these two methods in Maria Dominguez’s study.
Determine the study’s key findings
Look at what Dominguez actually found.
- Illuminated pastures had slightly fewer predator visits.
- But sheep clustered near the bright devices, which reduced grazing time and weight gain.
- Flocks with dogs roamed widely and gained more weight, even though some wolf tracks were still found nearby. These details show that lights reduce predator visits a bit more, but they have negative side effects for the sheep, while dogs allow better grazing and weight gain even with some predator presence.
Express the main conclusion in your own words
Ask: What is the author’s overall point about these two protection methods? The passage suggests that both methods help limit predator encounters, but the overall benefits to the sheep (especially weight gain and natural roaming) are greater when they are guarded by dogs than when they are protected by deterrent lights.
Match that main idea to the best answer choice
Now compare your summary to the answer choices:
- Eliminate any choice that says the lights are clearly the best, because the passage shows important drawbacks to lights.
- Eliminate any choice that claims predators are not very dangerous, since predator danger is never dismissed.
- Eliminate any choice that shifts focus to something like grazing-season length, which the passage never mentions. The only choice that accurately captures the passage’s main conclusion—that traditional guardian dogs provide greater overall benefits than deterrent lights, even though both help reduce predator encounters—is Choice C.