Echolocation Flashcards

1
Q

What is echolocation?

A

emission of acoustic signals in order to use the returning echoes to perceive the environment

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2
Q

echo ______, ________________, and ____________ and ___________________ differences enable an animal to determine azimuth and distance.

A
  • delays
  • intensity
  • frequency
  • left-and-right
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3
Q

List the following for megachiroptera:
- what kind of animals
- large or small?
- visual or non-visual?
- echolocating or non-echolocating?

A
  • flying foxes and fruit bats
  • fairly large
  • primarily visual
  • 1 echolocating species
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4
Q

List the following for microchiroptera:
- what kind of animals
- large or small?
- visual or non-visual?
- echolocating or non-echolocating?

A
  • “typical” bats
  • most are small
  • vision relatively poor
  • all echolocate
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5
Q

What kind of frequencies does bat echolocation depend on?

A

ultrasound

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6
Q

What is the range of bat echolocation in dB?

A

60-140 dB

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7
Q

Is call duration long or short?

A

short

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8
Q

TRUE or FALSE: Slow attenuation of high frequencies also results in greater changes in the power of returning echoes.

A

FALSE: RAPID attenuation

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9
Q

What features can be determined from echoes?

A
  1. distance
  2. subtended angle
  3. absolute size
  4. azimuth
  5. elevation
  6. velocity
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10
Q

TRUE or FALSE: very small amplitude + short delay = small insect is nearby

A

TRUE

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11
Q

TRUE or FALSE: very small amplitude + long delay = large object is nearby

A

FALSE: large object is FAR AWAY

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12
Q

How do bats use distance to echolocate?

A

compare the time between a call and its returning echo

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13
Q

How do bats use subtended angle to echolocate?

A

the intensity of the echo dictates how much of the echolocating call is broken by an object

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14
Q

How do bats use echolocation to determine absolute size of an object?

A

by combing DELAY and INTENSITY, the absolute size of an object can be calculated

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15
Q

How do bats use echolocation to determine the azimuth?

A

compare INTENSITY and TIMING differenes between LEFT and RIGHT to determine direction in x-y dimensions

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16
Q

How do bats use echolocation to determine elevation?

A
  • can move ears when receiving echoes to compare intensities between ears
  • ear structure can also enhance intensity differences
  • together these provide info on z-axis (up-down)
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17
Q

How do bats use echolocation to determine velocity?

A

doppler shift of echoes yields velocity

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18
Q

TRUE or FALSE: echo is higher frequency than call = target is moving further away from bat

A

FALSE: bat is gaining on target (hint: doppler shift)

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19
Q

label the following on slide 8 diagram:
- absolute size
- azimuthal angle
- elevation
- doppler shift and flutter

A

slide 8

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20
Q

Put the following in order of when a bat’s calls get closer in time:
- search phase
- terminal buzz phase
- approach phase

A
  1. search phase
  2. approach phase
  3. terminal buzz phase
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21
Q

What are 3 types of echolocating calls?

A
  1. clicks
  2. constant frequency (CF)
  3. frequency modulation (FM)
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22
Q

Describe the characteristics of clicks.

A
  • broad spectrum; not ultrasonic
  • found in the single echolocating fruit bat and birds
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23
Q

Describe the characteristic of constant frequency calls.

A

primarily a single frequency

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24
Q

Describe the characteristic of frequency modulation (FM) calls.

A

frequency sweeps

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25
Draw a frequency-time graph for FM bats. Label the 3 phases of the call.
graph A on slide 12 (frequency sweeps)
26
Draw a frequency-time graph for CF-FM bats. Label the 3 phases of the call.
graph B on slide 12 (downward sweep at end)
27
Where do FM bats typically forage?
in open areas or on forest edges
28
TRUE or FALSE: CF-FM bat calls tend to be high intensity to ensure that echoes from targets can be received.
FALSE: FM bats
29
TRUE or FALSE: CF-FM bats tend to have shorter duration calls, whereas FM bats tend to have longer duration calls
FALSE: - CF-FM = longer call - FM = shorter call
30
Why do FM bats have a shorter duration, broad frequency call?
the sweep of the call allows for BETTER RESOLUTION of the TIME DELAY between the call and echo
31
TRUE or FALSE: CF-FM bats use harmonics to make their echolocation even more precise.
FALSE: FM bats
32
TRUE or FALSE: CF-FM bat calls tend to be longer and the operational range is smaller than only FM
FALSE: operational range is GREATER than only FM
33
CF component of CF-FM bat calls permits more accurate determination of ______________________ and _________________________.
target velocity, fluttering movement
34
Where do CF-FM bats normally hunt/forage?
denser foliage
35
Draw the pulse and echo for when an insect's wing moves toward the bat vs away from the bat? (i.e. what occurs to the frequency and amplitude of the echo)?
- toward bat = higher frequency and amplitude echo - away from bat = lower frequency and amplitude echo (slide 16; hint = doppler shift)
36
Describe how echolocation works when bats glean their prey from leaves and twigs (or the ground).
- hover and emit continuous FM calls - no terminal buzz
37
TRUE or FALSE: when bats glean their prey from leaves and twigs (or the ground), there is no approach phase
FALSE: no terminal buzz phase
38
How do bats produce echolocating calls?
- generate motor pattern that is sent to the larynx - laryngeal muscles are 'superfast', allowing them to contract at an extremely high frequency (i.e. allow for TERMINAL BUZZ)
39
TRUE or FALSE: some CF-FM bats have bizarre noses that can be used to direct and detect echolocating calls
TRUE
40
Which features of echolocation can be shifted in different contexts?
- call duration - intensity - frequency
41
TRUE or FALSE: when there is more ambient noise, bats make their calls longer and more intense
FALSE: LESS intense
42
Draw a diagram to show how bats' echolocating calls are shifted in the presence of more and more ambient noise
slide 20; longer and less intense calls
43
TRUE or FALSE: beam width is larger in the search and approach phase, and smaller in the terminal buzz phase
FALSE: - larger in terminal buzz phase - smaller in search and approach phase
44
How do bats avoid getting confused by the echoes from other bats?
- when foraging with other bats, FM bats adjust FREQUENCY and TEMPORAL features of their calls - this allows them to separate out the call features of one another
45
TRUE or FALSE: the auditory system of the bat is very differnt from non-echolocating mamals
FALSE: very similar
46
label slide 25
slide 25
47
Bats move their ears between calls to enhance ____________ and _____________ differences between left and right
intensity and timing
48
What does the TRAGUS of the external ear do?
direct echoes and enhance intensity and timing differences (for calculating azimuth and elevation)
49
Why do FM bats contract the middle ear muscles during a call?
attenuates the loudness of their call so they are not deafened when echolocating
50
TRUE or FALSE: bats have poor high-frequency hearing
FALSE: low-frequency
51
Draw the threshold vs frequency graph comparing humans and horseshoe bats.
slide 29, graph A; horseshoe bat shift to right because they cannot detect low frequencies
52
Which part of the ear is very large to account for a large hearing range in bats?
cochlea
53
TRUE or FALSE: high frequency is encoded at the base of the cochlea (near outer ear); low frequency is encoded at the tip of the cochlea (near inner ear)
TRUE
54
What part of the ear reflects hearing range?
basilar membrane
55
TRUE or FALSE: in CF-FM bats, the FM frequency of echoes is expanded
FALSE: CF frequency expanded
56
Why is the CF frequency of echoes expanded in CF-FM bats?
provides greater sensitivity to CF that assists in Doppler shift analysis
57
Draw a diagram of the auditory pathway from the cochlear nuclei to the cortex
slide 35
58
What frequency range is the largest reflected area in the inferior colliculus of a bat?
60-63 kHz
59
TRUE or FALSE: specific neurons respond to specific calls
TRUE
60
The inferior colliculus is not only tuned to frequency, but also highly sensitive to __________________________.
timing between calls and echoes
61
TRUE or FALSE: inferior colliculus neurons have a very high threshold and therefore the timing of activity is responsive to even high amplitudes
FALSE: LOW threshold; responsive to even LOW amplitudes
62
Draw a graph of biosonar signals in bats using frequency vs time.
slide 42
63
TRUE or FALSE: difference between FM (FM-FM areas) encodes velocity, whereas difference in CF (CF-CF areas) encodes distance
FALSE: - FM-FM = distance - CF-CF = velocity
64
TRUE or FALSE: cortical organization in FM bats also have the doppler and CF regions
FALSE: LACK the DCSF and CF regions
65
____________ species have a bimodal distribution for over-representation of frequencies: one area for _________, a second for _________________.
gleaning; echoes; passive learning
66
Draw the distribution of number of sites and best frequency in FM bats.
slide 45