BAT FLIGHT AND ECHOLOCATION

http://www.arkive.org/species/ARK/mammals/Myotis_daubentonii/Myotis_daubentoni_08.html?movietype=wmMed

Structure of bat wings

Comparative structure of vertebrate wings

Bat & Bird comparison

Mechanical efficiency

http://www.arkive.org/species/GES/mammals/Petaurus_gracilis/Petaurus_gracilis_00.html?movietype=wmMed

Origin of bat flight

Gliding as an intermediate stage

Multiple independent origins among living mammals Marsupials – 1 Order, 3 Families Placentals – 2 Orders, 3 Families

Dermoptera vs. Chiroptera – gliding membrane

Wing shape and flight dynamics

Artibeus(low aspect ratio)

Eumops(high aspect ratio)

Wing aspect ratio (length/width)

Echolocation

FREQUENCY

Human hearing0.02 – 20 kHz

Bat echolocation9 – 200+ kHz

http://www.asel.udel.edu/speech/tutorials/acoustics/sn_h7.wav

1400 Hz (1.4 kHz)

AMPLITUDE(loudness)

20 dB – whisper 60 dB -- conversation 130 dB – pain threshold Bat echolocation 60 – 120 dB

Characteristics of sound

ATTENUATION of sound(rate of energy loss)

Increases with frequency

ECHO attenuation Increases with frequency

HOWEVER

Higher frequencies produceechoes from smaller objects.

Characteristics of sound

Characteristics of sound in echolocationHigh frequencies more effective in locating small targets but have limited range

Low frequencies increase detection range but limit resolution of target

Constant frequency (CF)allows for precise location via doppler shift (i.e., returning sound has a shifted freqeuncy)

Multiple frequencies (broad band) provide more information about target shape

Harmonics

Frequency modulation (FM) –frequecny sweep

Bat ear shapes

Yangochiroroptera Murina (Vespertilionidae) Lonchorhina (Phyllostomidae)

Yinpterochiroroptera Cardioderma (Megadermatidae) Hipposideros (Hipposideridae)

Bat facial structures

“ Tongue-clicking” echolocationRousettus (Pteropodidae)

Short duration pulseswith wide frequency range.Effective for obstacleavoidance inside cave roosts

Does not involve larynx.Sound pulses produced byin mouth with tongue

FM(frequency modulated)

Initial CF(“constant” frequency)

Teriminal FM

Basic types of “microchiropteran” calls

Broad FM(frequency modulated harmonics)

Nycteris (Nycteridae) Macroderma (Megadermatidae)

Perch-hunters & “whispering” bats Large ears for receiving low-frequency ambient sound from prey. Large eyes (also use vision to locate prey) Produce low amplitude FM “stealth” calls

Plecotus (Vespertilionidae)

harmonics

Low frequency FM batsHunt in open habitatProduce high amplitude calls at low frequencies (some audible to humans)Large ears “tuned” to low frequencies

Euderma maculatum (Vespertilionidae)

http://batcalls.org/prod/uploads/joesze.Euderma_maculatum_1.wav

Broad frequency FM batsProduce high amplitude calls with multiple harmonics over a broad frequency range, with downward-sweeping FM.

Provide detailed information on shape and size of prey

http://batcalls.org/prod/uploads/joesze.Myotis_ciliolabrum_5.wav

Myotis ciliolabrum

High duty cycle bats Fly in closed, cluttered habitat (forest interior). Emit very high frequency constant frequency (CF) calls, or CF and FM in combination, using Doppler shift to determine location and movement of prey.

Elaborate nose involved in beaming calls and ear shape “tuned” to receive narrow-band echoes

Rhinolophus (Rhinolophidae)

Hipposideros (Hipposideridae)

Rhinolophus megaphyllus

Rhinolophus hipposideros

High duty cycle bats (Rhinolophidae)Constant Frequency (CF)

http://batcalls.org/prod/uploads/mlwen.Rhme-08Nov03-0457.wav

http://batcalls.org/prod/uploads/willemhol.Rhin_hipp_Dordogne_08062005_A2_12000_290000.wav

High duty cycle bats (Hipposideridae)Constant Frequency + Frequency Modulated (CF/FM)

Second harmonic

First harmonic

CF component FM component

Hipposideros abae Hipposideros commersoni

Insulation from “self-deafening”

Dampening sound transmission through middle ear ossicles

Tensor tympani (increasing tension on tympanum)Stapedius (regulates contact of stapes with cochlea)

Isolation of theotic capsule from cranium

Bat evolution: flight first or echolocation first?

CF

FM no laryngeal echolocation

fossils

Comparative morphology (size of cochlea)

CF/FM

YINPTER

OC

HIR

OPTER

A YAN

GO

CH

IRER

OPTER

A“Microchiroptera” paraphyletic

THE ABSENCE OFLARYNGEAL

ECHOLOCATIONIN PTEROPODIDSIS APPARENTLY

DERIVED