Transcript Overview Acoustic Detection of Bats

Gobi Bat Project
and
Acoustic Detection of Bats
Cori Lausen
Birchdale Ecological Ltd.
www.batsRus.ca
Great Gobi Strictly Protected Area
Bat Project
Main Goals of Project:
1. To determine what species of bats are in the
GGSPA using mistnets and bat detectors.
2. To record echolocation (bat ultrasound) from each
species to know what each bat sounds like for
identification without mistnet capture.
3. To teach Mongolian biologists about bat acoustics
and how to use the bat detectors to learn more
about bats in Mongolia.
Great Gobi Strictly Protected Area
Bat Project May 2011
BAT DETECTORS: ANABAT and SM2BAT
Bat Detectors and Software
Donated to Mongolia:
Titley Scientific (Australia) - Anabat
Wildlife Acoustics (USA) - SM2BAT
Joe Szewczak (USA) – Sonobat (analysis software)
Two Types of Detectors
Wildlife Acoustics
SM2BAT
Full
spectrum
Zerocrossing
Titley Scientific
Anabat
Species of bats
captured in Gobi
Vespertilio murinus
Species of bats
captured in Gobi
Eptesicus gobiensis
Species of bats
captured in Gobi
Hypsugo alashanicus
Species of bats
captured in Gobi
Myotis mystacinus
Species Differences at a Glance
Myotis mystacinus
Hypsugo alashanicus
Eptesicus gobiensis
Vespertilio murinus
MINIMUM FREQUENCIES OF PULSES
Species Previously Known from
Great Gobi Strictly Protected Area
Recorded but not captured May 2011
Photo: Ariunbold
Plecotus kozlovi
Water as a Limiting Factor
Studies in the Southwest USA
(Rick Adams) have shown that
bats do not move when their
water source dries out, they just
stop reproducing each year.
This means we need to keep
checking for reproduction in dry
areas with ephemeral water.
Enhancing Gobi’s water
sources would be good for
bats… it is currently being
considered for bears (e.g. at
Baran Tooroi).
Khulan Holes
-keeping water open for bats
Making Bat-Friendly Water Troughs
• A way for them to
crawl out of water
(or they will drown)
• Appropriate size for
all species of bats to
benefit
Understanding bat echolocation
We can’t hear bats.
Frequency of sound:
Humans hear <20kHz
Speech is <5 kHz
Most bats echolocate >20kHz (ultrasound).
We therefore need to transform ultrasound into a
lower frequency using bat detectors.
Sound
• Sound is a wave.
Sound bounces off of objects providing echoes.
Object must be larger than one wavelength to reflect sound.
Sound
• Sound is a wave.
Sound bounces off of objects providing echoes.
Object must be larger than one wavelength to reflect sound.
A 35 kHz frequency has a wavelength of ~1 cm, and would therefore
best detect this size of object.
Wave Length
• Wave length Increases as frequency decreases
– 35kHz
wave length = 10 mm
– 70kHz
wave length = 5 mm
• Shorter wavelengths (Higher Frequencies)
– Can detect smaller objects
– Provide finer detail
• Longer wavelengths (Lower Frequencies)
– Travel further (Less absorbed by the air)
Example of ultrasound from Gobi Bats….
Frequency (kHz)
35 kHz allows bat to
detect objects 1 cm.
Time (s)
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Clutter:
-trees
-grass
-ground
-other bats
-detector
-insect prey
etc.
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Clutter:
-trees
-grass
-ground
-other bats
-detector
-insect prey
etc.
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Clutter:
-trees
-grass
-ground
-other bats
-detector
-insect prey
etc.
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Clutter:
-trees
-grass
-ground
-other bats
-detector
-insect prey
etc.
Frequency (kHz)
Properties of bat echolocation.
The effect of CLUTTER.
Time (s)
Clutter:
-trees
-grass
-ground
-other bats
-detector
-insect prey
etc.
In High Clutter:
• Species/genera/families often converge
– High slope
– Short duration
– Long frequency sweeps
– Raised frequency
Clutter …
makes identification of some species challenging
Little Brown
in low clutter
Little Brown
in high clutter
Northern Myotis
(a bat that tends to stay
in high clutter)
Search-phase Continuum
•Two species of
different families
Big Brown Bat
•Produced at
different levels of
clutter
•Variation within an
individual is much
greater than
between families!
Mexican Freetail Bat
Time (s)
Frequency (kHz)
Feeding Buzz
Eptesicus fuscus
Search-phase Continuum
•Two species of
different families
•Produced at
different levels of
clutter
•Variation within
an individual is
much greater than
between families!
Tadarida brasiliensis
SLIDE BY C. CORBEN, ANABAT WORKSHOPS
To Understand Species Diversity in
Mongolia
Collect reference calls from captured bats
-bat distributions can then be determined using bat
detectors
-capture may not be required in many places of
the country if a good reference call collection is
established
-to evaluate whether taxonomic classifications are
accurate, recording ultrasound from potentially cryptic
species is important (e.g. Soprano vs Commom
Pipistrelles in Europe)
Obtaining Reference
Calls from Captures
• Hand-released *
• Zip-lining
• Bat-kiting
*Try to obtain ‘free-flying’ calls so wait until the
bat has flown out of the hand but is still within
recording distance of microphone. Ideal if
they circle back over you, or you can run after
them!
Reference Calls from Bats
Tethering Techniques
Zip-line
Bat-kite
Effects of Releasing a Bat
Analook
View Unknown and Reference Files
Sonobat
View Unknown and Reference Files