Echolocation

Question 1

Echolocation

Answer 1

• Use echoes of sounds produced to locate objects

Question 2

Who does echolocation?

Answer 2

–  Chiroptera – navigation & hunting
– Odontoceti – navigation & hunting?
– Soricomorpha – navigation
– Afrosoricida – navigation
– Rodentia – navigation

Question 3

• Water is much denser than air

Answer 3

– Sound travels 4X faster in water

– Sound attenuates more rapidly in air

Question 4

• Aquatic echolocating mammal

Answer 4

– Signals transmitted farther and return faster

– Less energy used for signal of given intensity

Question 5

Echolocation calls can be described in terms of

Answer 5

time, frequency, and intensity

Question 6

Echolocation in bats

Answer 6

• Brief pulses of sound
•Frequency varies widely
among species
• Intensity (decibels) 
• Bandwidth (breadth of frequencies
produced)

Question 7

Range Limits

• Echolocation is a short-range system in air

Answer 7

– Targets detected at close range

– Requires slower, more maneuverable flight

Question 8

High-Frequency Sound

Answer 8

• Rapidly attenuated in air

Question 9

• Why use high frequencies?

Answer 9

– High frequency = short wavelength
– Objects equal in size to wavelength reflect that wavelength well
– Low frequency sounds have long wavelengths
• Tend to bend around small objects instead of being reflected

Question 10

How do bats distinguish incoming from

outgoing calls?

Answer 10

1. Duty cycles (high or low)

2. Self deafening

Question 11

• Clicks

Answer 11

– Produced in nasal passages in odontocetes

– Produced with tongue in two genera of pteropodids

Question 12

• Vocal signals

Answer 12

– Produced in larynx in most echolocating

chiropterans and soricomorphs

Question 13

– Low duty cycle approach

Answer 13

• Produce signals small percentage of time

* Do not broadcast and receive signals simultaneously

Question 14

– High duty cycle approach

Answer 14

• Produce signals larger percentage of time
• Produce pulses and receive echoes simultaneously
• Doppler-shifted echoes
-Distinguish echo by frequency

Question 15

Self-Deafening
• Middle and inner ear are insulated from the rest of
the skull

Answer 15

• Two ear muscles dampen sounds
– Tensor tympani
• Changes tension in tympanic membrane
– Stapedius
• Changes contact between stapes and oval window

Question 16

• Bat echolocation pulses emitted via:

Answer 16

– Nose
• Members of Nycteridae, Megadermatidae,
Rhinolophidae, Hipposideridae, and Phyllostomidae
– Mouth
• All the others

Question 17

Faces, Ears, and Echolocation

Answer 17

• Mouth emitters use lips like megaphones
• Noseleaves and horseshoes focus sound
• Tragus
– Sound localization

Question 18

Both echolocation and flight contributed to
evolution and diversity of bats (>1000
species)

Answer 18

• Echolocation calls probably derived from

vocal communication

Question 19

Evolution of Echolocation
Hypothesis:
• Echolocation-first hypothesis
– 
• Flight-first hypothesis
– 
• Tandem-evolution hypothesis
–

Answer 19

– Bat ancestors were small, nocturnal gliders

– Bat ancestor capable of powered flight

– Echolocation and flight evolved together

Question 20

• Evidence for Flight First Hypothesis

Answer 20

– Early Eocene bat Onychonycteris could fly:

– Onychonycteris could not echolocate

Question 21

• Many nocturnal moths have “ears”

Answer 21

– “Ears” are on thorax
– Sensitive to wide range of frequencies
– Aid detection of bat ultrasonic pulses

Question 22

• Some moth species have sound-producing

organ on thorax

Answer 22

– Produce ultrasonic clicks

– Interferes with bat signals/echoes

Question 23

Coevolution

– Bats prey on nocturnal moths

Answer 23

– Moths responded by detecting bats’ signals
• Avoidance maneuvers
• Jamming bat echolocation
– Bats responded by:
• Using allotonic frequencies
• Lower duty cycles

Question 24

Sound in Cetaceans

Answer 24

Two basic types of sounds
– Narrowband continuous tones (whistles)
– Broadband clicks (audible to humans)

Question 25

``` Echolocation in Cetaceans • Types of biosonar – Active sonar • – Passive sonar • – Ambient noise imaging • ```

Answer 25

• Typical echolocation – hearing echoes of emitted sound pulses • Hearing sounds without producing sounds • Ability to “ see ” underwater with sound

Question 26

• Where are echolocation clicks produced? | in cetaceans

Answer 26

– Upper nasal passages ventral to blowhole – Bilateral phonic lip/dorsal bursae (PLDB) complex

Question 27

``` in cetaceans • Melon serves to focus sound pulse into beam – • Sperm whales have single large PLDB – ```

Answer 27

– Forms an “acoustic lens” that shapes the beam – PLDB anterior to spermaceti organ and junk

Question 28

Echolocation in Cetaceans •Rapid bursts of clicks (called creaks) may be analogous to terminal buzz in bats

Answer 28

•Intense blasts of sounds (called bangs) | may disorient or stun prey

Question 29

Cetacean Hearing • Bullae are insulated from skull by sinuses – • Thin region on posterior dentary (pan bone) –

Answer 29

– Sinuses contain oil-mucus-air emulsion – Acts as acoustic window

Question 30

• Shrews may echolocate for

Answer 30

target | detection

Question 31

• Tenrecs echolocate by

Answer 31

tongue clicks

Question 32

• Some rodents produce ultrasonic sounds

Answer 32

– Probably for communication

Question 33

Pinnipeds

Answer 33

– No direct evidence for echolocation

Question 34

• Sirenians

Answer 34

– Complex, single-note calls – No clear evidence of echolocation (target detection)