TOEFL Reading Practice Online | Q&A 013

This is an original TOEFL-style academic reading passage with practice comprehension questions, not reproduced from any official test. Try about 1.5 minutes per question as a self-practice pace, and see the reading practice hub or more reading practice articles for additional sets.

Passage

Echolocation: How Bats Navigate by Sound

[1] Many bat species hunt flying insects at night in conditions too dark for vision to be of much use, yet they capture prey with remarkable accuracy. Rather than relying on sight, these bats navigate and hunt using echolocation: they produce short, high-frequency calls, generally well above the range of human hearing, and interpret the echoes that bounce back from objects in their surroundings.

[2] A typical echolocation call is produced in the larynx and emitted through the mouth or, in some species, through specialized structures in the nose. As the sound wave travels outward, it strikes nearby objects, such as tree branches, cave walls, or a moth in flight, and a portion of that sound reflects back toward the bat. By measuring the delay between the outgoing call and the returning echo, a bat's brain calculates the distance to an object with great precision. Subtle differences in the echo's loudness and frequency provide further information about an object's size and texture, while shifts in frequency caused by an object's motion, a phenomenon similar to the change in pitch of a passing siren, help the bat judge whether prey is approaching, retreating, or moving sideways.

[3] Producing calls loud enough to generate a useful echo poses a problem: the sound could easily overwhelm the bat's own sensitive hearing before the faint returning echo arrives. Many bats solve this through a precisely timed reflex in which small muscles in the middle ear contract just before and during each outgoing call, temporarily reducing the ear's sensitivity, and then relax rapidly so the ear can register the much quieter echo. During the final seconds of an insect chase, some bats emit calls more than one hundred times per second, which means this contraction-and-release cycle must occur with extraordinary speed and consistency.

[4] Not all bats use the same kind of call. Some species sweep quickly through a wide range of frequencies in each call, a strategy well suited to resolving fine detail at close range, such as distinguishing a twig from a moth. Other species instead hold a single frequency steady for a longer call, a strategy that makes frequency shifts caused by a moving target easier to detect at greater distances. Some bats that hunt moths capable of hearing ultrasound use unusually quiet calls, a kind of "stealth" echolocation that appears to reduce the chance that prey will detect the approaching predator and take evasive action.

[5] Beyond its role in bat biology, echolocation is often compared with sonar, a human technology that also locates objects by timing reflected sound. Bat echolocation has also inspired devices intended to help visually impaired people detect obstacles using reflected sound, an indication of how research into animal senses can reach well beyond its original subject.

Questions

1. What does the passage mainly discuss?

• (A) The diet of insect-eating bats
• (B) The evolution of bat wings
• (C) How bats use echolocation to navigate and hunt, and how the ability varies between species
• (D) A comparison of bat and dolphin habitats

2. The word "reflects" in paragraph 2 is closest in meaning to

• (A) bounces
• (B) absorbs
• (C) disappears
• (D) weakens

3. According to paragraph 2, how does a bat judge the distance to an object?

• (A) By comparing the loudness of two different calls
• (B) By counting how many echoes it receives each second
• (C) By sensing changes in air temperature
• (D) By measuring the delay between an outgoing call and the returning echo

4. Why does the author compare frequency shifts caused by motion to "the change in pitch of a passing siren" in paragraph 2?

• (A) To question the accuracy of echolocation
• (B) To explain an unfamiliar effect with a familiar example
• (C) To argue that sirens and bat calls are produced in the same way
• (D) To describe how bats avoid emergency vehicles

5. According to the passage, an echo can give a bat information about all of the following EXCEPT

• (A) the distance to an object
• (B) the size and texture of an object
• (C) whether prey is approaching or moving away
• (D) the exact species of insect it has detected

6. The word "this" in the last sentence of paragraph 3 refers to

• (A) the bat's hunting strategy
• (B) the moth's evasive flight
• (C) the reflex in which small middle-ear muscles tighten during each call and then relax
• (D) the rate at which the bat beats its wings

7. It can be inferred from paragraph 4 that the unusually quiet calls of some bats

• (A) are less useful than loud calls for detecting any kind of prey
• (B) probably developed partly in response to prey that can hear ultrasound
• (C) are used only during the day
• (D) are louder than the calls of most other bats

8. The word "evasive" in paragraph 4 is closest in meaning to

• (A) intended to escape
• (B) aggressive
• (C) noisy
• (D) accidental

9. According to paragraph 5, which of the following has bat echolocation inspired?

• (A) Treatments for hearing loss
• (B) Methods for tracking insect migration
• (C) Night-vision cameras
• (D) Devices that help visually impaired people detect obstacles using reflected sound

Answers and explanations

1. (C) Paragraphs 1–3 explain how echolocation works, and paragraph 4 describes how call types differ between species.
2. (A) When part of the sound "reflects back toward the bat," it bounces back.
3. (D) Paragraph 2 says the bat measures "the delay between the outgoing call and the returning echo" to calculate distance.
4. (B) Most readers have heard a siren change pitch as it passes, so the comparison makes the frequency shift easier to understand.
5. (D) Paragraph 2 mentions distance, size, texture, and movement. Nothing suggests an echo identifies the exact species of insect.
6. (C) "This contraction-and-release cycle" refers to the reflex described earlier in paragraph 3, in which middle-ear muscles contract during each call and then relax to hear the echo.
7. (B) Paragraph 4 says these faint calls "appear to reduce the chance that prey will detect the approaching predator," linking them to moths that can hear ultrasound.
8. (A) "Evasive action" is action taken to escape or avoid something, here the approaching bat.
9. (D) Paragraph 5 says echolocation has inspired devices meant to help visually impaired people detect obstacles. It compares echolocation with sonar but does not claim bats inspired any of the other options.