BAT FLIGHT AND ECHOLOCATION
http://www.arkive.org/species/ARK/mammals/Myotis_daubentonii/Myotis_daubentoni_08.html?movietype=wmMed
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
Wing shape and flight dynamics
Artibeus(low aspect ratio)
Eumops(high aspect ratio)
Wing aspect ratio (length/width)
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 echolocation
High 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
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 bats
Produce 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
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