Vocalization in Frogs
The tungara frog is a small terrestrial vertebrate that is found in Central America. Tungara frogs breed in small pools, and breeding groups range from a single male to choruses of several hundred males. The advertisement call of a male tungara frog
is a strange noise, a whine that starts at a frequency of 900 hertz and sweeps downward to 400 hertz in about 400 milliseconds. The whine may be produced by itself, or it may be followed by one or several chucks or clucking sounds. When a male tungara frog is calling alone in a pond, it usually gives only the whine portion of the call, but as additional males join a chorus, more and more of the frogs produce calls that include chucks. Scientists noted that male tungara frogs calling in a breeding pond added chucks to their calls when they heard the recorded calls of other males played back. That observation suggested that it was the presence of other calling males that incited frogs to make their calls more complex by adding chucks to the end of the whine.
What advantage would a male frog in a chorus gain from using a whine-chuck call instead of a whine? Perhaps the complex call is more attractive to female frogs than the simple call. Michael Ryan and Stanley Rand tested that hypothesis by placing female tungara frogs in a test arena with a speaker at each side. One speaker broadcast a pre-recorded whine call, and the second speaker broadcast a whine-chuck. When female frogs were released individually in the center of the arena, fourteen of the fifteen frogs tested moved toward the speaker broadcasting the whine-chuck call.
If female frogs are attracted to whine-chuck calls in preference to whine calls, why do male frogs give whine-chuck calls only when other males are present? Why not always give the most attractive call possible? One possibility is that whine-chuck calls require more energy than whines, and males save energy by only using whine-chucks when competition with other males makes the energy expenditure necessary. However, measurements of the energy expenditure of calling of male tungara frogs showed that energy cost was not related to the number of chucks. Another possibility is that male frogs giving whine-chuck calls are more vulnerable to predators than frogs giving only whine calls. Tungara frogs in breeding choruses are preyed upon by a species of frog-eating bats, Trachops cirrhosis, and it was demonstrated that the bats locate the frogs by homing on their vocalizations.
In a series of playback experiments, Michael Ryan and Merlin Tuttle placed pairs of speakers in the forest and broadcast vocalizations of tungara frogs. One speaker played a recording of a whine and the other a recording of a whine-chuck. The bats responded as if the speakers were frogs: they flew toward the speakers and even landed on them. In five experiments at different sites, the bats approached speakers broadcasting whine-chuck (168 approaches versus 81). Thus, female frogs are not alone in finding whine-chuck calls more attractive than simple whines—an important predator of frogs also responds more strongly to the complex calls.
Ryan and his colleagues measured the rates of predation in tungara frog choruses of different sizes. Large choruses of frogs did not attract more bats than small choruses, and consequently the risk of predation for an individual frog was less in a large chorus than in a small one. Predation was an astonishing 19 percent of the frogs per night in the smallest chorus and a substantial 1.5 percent per night even in the largest chorus. When a male frog shifts from a simple whine to a whine-chuck call, it increases its risk of attracting a female, but it simultaneously increases its rate of attracting a predator. In small choruses, the competition from other males for females is relatively small, and the risk of predation is relatively large. Under these conditions it is apparently advantageous for a male tungara frog to give simple whines. However, as chorus size increases,
competition with other males also increases while the risk of predation falls. In that situation, the advantage of giving a complex call apparently outweighs the risks.
【Paragraph 1】
The tungara frog is a small terrestrial vertebrate that is found in Central America. Tungara frogs breed in small pools, and breeding groups range from a single male to choruses of several hundred males. The advertisement call of a male tungara frog
is a strange noise, a whine that starts at a frequency of 900 hertz and sweeps downward to 400 hertz in about 400 milliseconds. The whine may be produced by itself, or it may be followed by one or several chucks or clucking sounds. When a male tungara frog is calling alone in a pond, it usually gives only the whine portion of the call, but as additional males join a chorus, more and more of the frogs produce calls that include chucks. Scientists noted that male tungara frogs calling in a breeding pond added chucks to their calls when they heard the recorded calls of other males played back. That observation suggested that it was the presence of other calling males that incited frogs to make their calls more complex by adding chucks to the end of the whine.
1. According to paragraph 1, male tungara frogs add chucks to the whine they produce when
A. potential mates are unable to hear the frequency of their whine sounds
B. other males produce louder whine sounds than they do
C. the frogs breed in large pools rather than small ones
D. other males are present in their breeding pool
【Paragraph 2】
What advantage would a male frog in a chorus gain from using a whine-chuck call instead of a whine? Perhaps the complex call is more attractive to female frogs than the simple call. Michael Ryan and Stanley Rand tested that hypothesis by placing female tungara frogs in a test arena with a speaker at each side. One speaker broadcast a pre-recorded whine call, and the second speaker broadcast a whine-chuck. When female frogs were released individually in the center of the arena, fourteen of the fifteen frogs tested moved toward the speaker broadcasting the whine-chuck call.
2. What is the relationship of paragraph 2 in the passage to paragraph 1?
A. Paragraph 2 provides additional support for a scientific hypothesis discussed in paragraph 1.
B. Paragraph 2 questions the accuracy of a scientific observation discussed in paragraph1.
C. Paragraph 2 provides a possible explanation for a scientific observation discussed in paragraph 1.
D. Paragraph 2 identifies some strengths and weaknesses of a scientific hypothesis discussed in paragraph 1.
【Paragraph 3】
If female frogs are attracted to whine-chuck calls in preference to whine calls, why do male frogs give whine-chuck calls only when other males are present? Why not always give the most attractive call possible? One possibility is that whine-chuck calls require more energy than whines, and males save energy by only using whine-chucks when
competition with other males makes the energy expenditure necessary. However, measurements of the energy expenditure of calling of male tungara frogs showed that energy cost was not related to the number of chucks. Another possibility is that
male frogs giving whine-chuck calls are more vulnerable to predators than frogs giving only whine calls. Tungara frogs in breeding choruses are preyed upon by a species of frog-eating bats, Trachops cirrhosis, and it was demonstrated that the bats
locate the frogs by homing on their vocalizations.
3. To be attracted to whine-chuck calls “in preference to” whine calls means
A. to like whine-chuck calls instead of whine calls
B. to like whine-chuck calls in addition to whine calls
C. to like whine-chuck calls followed by whine calls
D. to like whine-chuck calls more than whine calls
4. Which of the sentences below best expresses the essential information in the highlighted sentence in the passage?
Incorrect choices change the meaning in important ways or leave out essential information.
A. Males may save energy when competing for mates by using only whine-chuck calls rather than both whines and whinechucks.
B. Males expend as much of their energy on whine-chuck calls as on whine calls when competing with other males.
C. Males save energy by using whine-chuck calls only when competing with other males.
D. Males that save energy by using only whines are less able to compete with other males.
【Paragraph 4】
In a series of playback experiments, Michael Ryan and Merlin Tuttle placed pairs of speakers in the forest and broadcast vocalizations of tungara frogs. One speaker played a recording of a whine and the other a recording of a whinechuck. The bats responded as if the speakers were frogs: they flew toward the speakers and even landed on them. In five experiments at different sites, the bats approached speakers broadcasting whine-chuck (168 approaches versus 81). Thus, female frogs are not alone in finding whine-chuck calls more attractive than simple whines—an important predator of frogs also responds more strongly to the complex calls.
5. According to paragraph 4, all of the following are true of the playback experiments EXCEPT
A. Female frogs and predator bats approached the broadcasting speakers.
B. The bats responded more strongly to the whine-chuck calls than they responded to the whine calls.
C. Each speaker played a different kind of male frog call.
D. The same experiment was repeated at different locations.
6. According to paragraph 4, the playback experiments of Ryan and Tuttle demonstrated which of the following?
A. Tungara frogs use both whines and whine-chucks in their vocalizations.
B. Female tungara frogs are attracted to both whine and whine-chuck vocalizations.
C. Female tungara frogs and predators of tungara frogs are attracted to different types of vocalizations.
D. Frog-eating bats are attracted to whine-chuck calls more than to whine alone.
【Paragraph 5】
Ryan and his colleagues measured the rates of predation in tungara frog choruses of different sizes. Large choruses of frogs did not attract more bats than small choruses, and consequently the risk of predation for an individual frog was less in a large chorus than in a small one. Predation was an astonishing 19 percent of the frogs per night in the smallest chorus and a substantial 1.5 percent per night even in the largest chorus. When a male frog shifts from a simple whine to a whine-chuck call, it increases its risk of attracting a female, but it simultaneously increases its rate of attracting a predator. In
small choruses, the competition from other males for females is relatively small, and the risk of predation is relatively large. Under these conditions it is apparently advantageous for a male tungara frog to give simple whines. However, as chorus size increases, competition with other males also increases while the risk of predation falls. In that situation, the advantage of giving a complex call apparently outweighs the risks.
7. According to paragraph 5, all of the following are true about tungara frog vocalizations EXCEPT
A. The larger the frog chorus, the smaller the chance there is of a particular frog being eaten by a predatory bat.
B. The larger the frog chorus, the louder each individual frog calls.
C. The smaller the frog chorus, the easier it is for a frog to attract a female.
D. The smaller the frog chorus, the more likely it becomes that frog using the whine-chuck vocalization will be attacked by a bat
8. Which of the following can be inferred from paragraph 5 about the behavior of male tungara frogs?
A. When in small choruses they use less effective mating calls to decrease their risk of predation.
B. They avoid joining a large chorus in a breeding pool because it increases the risk of predation.
C. They avoid the use of the whine-chuck call whenever there is the risk of predators.
D. They attempt to avoid predation by making their calls at night.
【Paragraph 5】
Ryan and his colleagues measured the rates of predation in tungara frog choruses of different sizes. Large choruses of frogs did not attract more bats than small choruses, and consequently the risk of predation for an individual frog was less in a large chorus than in a small one. Predation was an astonishing 19 percent of the frogs per night in the smallest chorus and a substantial 1.5 percent per night even in the largest chorus. ■When a male frog shifts from a simple whine to a whine-chuck call, it increases its risk of attracting a female, but it simultaneously increases its risk of attracting a predator. ■In small choruses, the competition from other males for females is relatively small, and the risk of predation is relatively large. ■Under these conditions it is apparently advantageous for a male tungara frog to give simple whines. ■However, as
chorus size increases, competition with other males also increases while the risk of predation falls. In that situation, the advantage of giving a complex call apparently outweighs the risks.
9. Look at the four squares【■】that indicate where the following sentence could be added to the passage.
Predation, therefore, is a risk in choruses of all sizes, but the risk varies depending on the type of call used.
Where would the sentence best fit?
10.【Directions】An introductory sentence for a brief summary of the passage is provided below. Complete the summary by selecting the THREE answer choices that express the most important ideas in the passage. Some sentences do not belong in the summary because the express ideas that are not presented in the passage or are minor ideas in the passage. This question is worth 2 points.
In order to attract females, male tungara frogs use two kinds of calls: a whine and a whine-chuck.
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Answer Choices
A. Tungara frogs generally use simple calls when they wish to attract a mate, and complex calls when they wish to avoid predation.
B. The hypothesis that whine calls are used to save energy when males are not in immediate competition with each other has been disproved by showing that chuck calls do not require more energy.
C. Most males gather in groups of several hundreds when calling because the rate of predation from bats is so high in small groups.
D. Two hypotheses have been put forward about why females and frog-eating bats are more attracted to males using whine-chuck calls.
E. Tungara females overwhelmingly favor the whine-chuck call used by the males, but so do certain bats that prey upon tungara frogs.
F. Male tungara frogs use the whine-chuck call in large groups, where their risk of predation is lower, and the whine call in small groups, where their risk is higher.
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