Bat Survey Technology An Introduction. Dr Tina Aughney

Transcription

1 Bat Survey Technology An Introduction Dr Tina Aughney

2 Ireland s bats 11 species of bats Pipistrelle bats Common pipistrelle Soprano pipistrelle Nathusius pipistrelle Myotis bats Natterer s bat Whiskered bat Daubenton s bat Brandt s bat Brown long-eared bat Leisler s bat Lesser horseshoe bat Greater horseshoe bat

3 All European bats use echolocation i.e. rapidly repeated bursts of sound pulses, when flying. Bats emit short, high frequency sounds and use the echoes to make a sound image of their environment. Echolocation

4 Which bat is which? To correctly identify bats we need to know a little about where and how they fly, because the sounds they make are related to flight style. A bat makes an echolocation call with each beat of its wings. Bats flying in enclosed spaces tend to beat their wings more rapidly than a bat out in the open.

5 FM (sweeps) and CF (levelled)

6 HOW DO BATS USE SOUND? Constant frequency (CF) call Frequency modulated (FM) call (FM/CF) call Sonograms of ultrasonic calls of bat species (time expanded recordings)

7 How do bats use sound? The habitats that bats tend to use are: Open Closed Edge Water

8 Closed Environments Open Environments Requires fine detail in confined space: quiet FM calls, don t have to travel far Need echoes that travel long distances: loud, low frequency CF calls e.g. Myotis spp. e.g. Nyctalus spp.

9 Leisler s bat (Nyctalus leisleri) Common pipistrelle (Pipistrellus pipistrellus) Natterer s bat (Myotis nattereri)

10 Soprano pipistrelle moving from clutter to open environment

11 HOW DO BATS USE SOUND? Use time difference between sound emission and returning echo to calculate distance Wavelength has to be equal or less than the size of the insect higher frequency calls = more resolution higher amplitude calls = travel further Compromise between calls of high frequency/low amplitude low frequency/high amplitude

12 HOW DO BATS USE SOUND? Bats determine where the insect is by calculating time difference between call and echo How do they know an insect isn t something else? Wavelength must be <=size of insect e.g. Insect 1cm (0.01m) 340/0.01 = 34,000hz (34kHz) NB: freq = speed of sound (340 ms -1 )/wavelength

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14 What is a bat survey? A bat survey is sampling the survey area for the presence of bats, identifying the species and where possible the population status of local bat populations. E.g. In relation to planning works or a development, the aim of surveying is to identify and assess the potential impacts the proposed works is likely to have on local populations of bat species present on and around the site and provide mitigation measures where required.

15 Where are bats found?

16 What is a bat survey? Condt. A bat survey generally involves the following: Daytime surveys to identify potential roosting sites, potential commuting routes and potential feeding areas. Signs of bat usage of buildings and trees as resting sites include bat droppings and staining. Direct searching for roosting bats can be undertaken using endoscopes and torches. Night-time survey, undertaken in the appropriate season and during fine, dry weather conditions, is completed using bat detectors, an instrument that detects the echolocation calls of flying bats and allows the observer to identify the species of bat Acoustic Surveying.

17 What is a bat survey? Condt. There are a number of different types of bat surveys: roost surveys (the resting place of a bat); commuting route surveys (travel paths to and from roosts and feeding areas) and foraging surveys (habitats where bats feed). Since bats are nocturnal mammals, much of the survey work is completed during the hours of darkness using acoustic technology (i.e. bat detectors). Scoping appropriate surveying for the survey site and for the time of year. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Hibernation / Spring Bat activity only in mild weather Bat Activity Surveys Autumn / Hibernation Bats become more active leading into the maternity season leading into the Mating season Mating season followed by hibernation in cold weather

18 The Bat Survey Desktop Study Site assessment Are their potential roosting places on-site Are their suitable habitats for foraging and commuting bats Bat Survey Type of survey required Type of equipment to be used Duration of the survey single night, full season survey Bat Survey Report

19 Types of Surveys Dusk & Dawn surveys Observer with a bat detector e.g. building surveys Stationary Units Units left on-site for a duration of time and set to continuously record e.g. Songmeter SM2 Bat Walking Transects Set routes walked with a bat detector e.g. Wind Farms Driven Transects Set route driven with a recording unit attached to the vehicles to record bats encountered

20 Echolocation Detector types: Tuneable (heterodyne) detectors Frequency Division bat detectors Time Expansion bat detectors Real Time recording devices

21 Real time ultrasound recording e.g. Pettersson D1000x, Laptop with DAQ card Time Expansion e.g. Pettersson D240x, Tranquillity Transect Frequency Division (+ Amplitude) e.g. Batbox Duet, Pettersson D230 Frequency Division ( - Amplitude) e.g. Anabat Heterodyne e.g. BatBox III, Magenta, Skye

22 Heterodyne Bat Detectors Grabs a small range of frequencies. Range of frequency heard depends on the position of the dial. Cannot survey for all species/frequencies simultaneously Resultant sound allows us to identify the repetition rate and rhythm of the call. On heterodyne, the Daubenton s bat can be described as a rapid series of click similar to a machine gun.

23 Detector tuned to 45kHz Detector tuned to 25kHz Bandwidth of detector usually (i.e. 5 khz either side of frequency detector is tuned at).

24 Heterodyne Detectors Magenta Bat Box 3D SSF Bat Pettersson D Bat Scanner Elekon's Bat Scanner - You just turn on the device and listen. The ultrasonic sounds are automatically transformed into the audible range, without the need for any adjustments. The mixing frequency of this heterodyne detector is determined and readjusted automatically by the call frequency of the bats. This offers many advantages: - Immediate display of the main frequency, even with only a brief flyby. This also helps to get a first estimation of the species. - Miss no bat, just because the wrong frequency is selected. - No tedious search for the optimal setting, which is especially helpful in the dark.

25 Frequency Division Bat Detectors Bat Baton Bat Box Duet Pettersson D Anabat Express Anabat SD Frequency Division is a broadband method as the entire ultrasonic range audible all the time Calls are transformed in real time i.e. the calls are heard through the detector at the same time they were emitted by the bat. By listening to the full range of frequencies you won't miss a bat while tuned into the wrong frequency.

26 Time ExpansionBat Detectors D1000x D240x Time Expansion Time Expansion detection is a `broadband' method as the entire ultrasonic range audible all the time (in contrast to a Heterodyne detector, which is sensitive only to a limited range of frequencies at each time). Time Expansion detectors first stores a portion of the ultrasonic signal in its digital memory and then replays it at a slower speed, i.e. it is does not transform the calls in real time. The delay depends on the actual storage time, and if this is very short (up to around 100 msec), the replay is also made fairly quickly and the detector gives an "almost real time" response. Time expanded calls produce the highest quality sonograms.

27 BUDGET Active Bat Monitoring VS Passive Bat Monitoring ZC Crossing Time Expansion Screen to actively view bat calls Full Spectrum PURPOSE DURATION Windows Apple

28 The Anabat Walkabout, Batbox XD, Pettersson M500 and Wildlife Acoustics EM Touch all have realtime sonogram display (Batbox XD, Pettersson M500 & Wildlife Acoustics EM Touch when connected to suitable device) and the Batbox Griffin, Elekon Batlogger M and Pettersson D1000X do not. The EM Touch connects to compatible Apple ios devices. If the real-time sonogram display is important to you, I recommend either the Anabat Walkabout or the Wildlife Acoustics EM3. If you don't want the display it would be the Batbox Griffin or Elekon Batlogger M (both of which can be used passively as well).

29 D240X Ultrasound Detector Very popular heterodyne and time expansion detector with backlit, large digit, accurate digital display, showing the tuned frequency in the heterodyne mode. The frequency and volume controls are on the side of the case, making it easy to adjust. Using stereo headphones, the heterodyne signal is heard on the left channel and the time expansion signal on the right channel. When the built-in speaker is used, a switch is used to select the heterodyne or time expansion signal. A digital recorder can be connected to the D240X to record the time expanded calls for analysis on a PC. 1,194.00

30 Wildlife Acoustics EM3 The EM3+ records bat passes in 16-bit full spectrum while simultaneously listening to bat calls in the method of your choice: Heterodyne, Time Expansion or Full Spectrum. The calls can be monitored during a survey with headphones or using the built-in speaker. Has a built-in spectrogram that displays current and recent bat passes. Recording of bat calls on an SDHC card GPS receiver can be attached. SongScope or Kliedoscope 1, Can be used for walking transects or car transects - GPS Can be used for dusk and dawn surveys heterodyne mode + recording Can be left out in the field to monitor for 20 hours real time recording Recording schedule easily set e.g. Sunset to sunrise

31 BatLogger M Features: Records unaltered bat echolocation calls (real-time, full spectrum). Can be used as a heterodyne bat detector (with automatic tuning) with speaker or headphones. Recording of bat calls on an SD card Every recording is geo-referenced by built-in GPS receiver. Additionally, the temperature at the time of recording is also recorded. Free software Bat Explorer 1, Can be used for walking transects or car transects - GPS Can be used for dusk and dawn surveys heterodyne mode + recording Can be left out in the field to monitor for 20 hours real time recording Recording schedule easily set e.g. Sunset to sunrise

32 BatLogger M The free BatExplorer Software allows you to manage Batlogger M recordings easily and quickly. You can listen to the recordings and expanded in time. Analysis is easy with BatExplorer because the software automatically detects bat calls and displays them. Customizable spectrogram with zoom and measuring aids facilitate manual species identification. BatExplorer also includes computer-aided identification of species with the help of an integrated bat species library ONLY BATLOGGER recordings can be used.

33 Passive Full Spectrum - SongMeter Bat+ 2 / 3 / SF4 1, , , Features: * Ideal for passive monitoring * Records WAC, WAV and/or ZCA * Enhanced waterproofing * Omni-directional microphone * Kaleidoscope Software ( 1068) SongScope Software ( ) Can be left out in the field to monitor for a minimum of 20 hours real time recording Recording schedule easily set e.g. Sunset to sunrise

34 Passive ZC , The Anabat Express and the Wildlife Acoustics SM4BAT ZC are both zero crossing recorders for leaving out on site. They both perform the same function and give the same results - ZC files of ultrasonic calls, i.e. bats. The differences are in the design, construction and weight of the units. The Express is a nice lightweight unit (476g with batteries) that's easily and discreetly deployed and it has a built-in GPS unit. It is programmed via a computer and can be deployed for up to 14 nights. The SM4BAT ZC is heavier (1.2kg with batteries) and more obtrusive and the GPS is optional (uses the same GPS as the EM3). Programmed on the front panel and easy to check and reprogram in the field. Has an integral security case. Deployable for up to 50 nights.

35 USB Microphones A Windows tablet PC with BatSound Touch and the M500 makes an easy to use and powerful bat detector with realtime audio as well as real-time spectrogram. M50 USB microphone Dodotronic microphone Connect it to your PC, iphone, ipad, Android smartphone or tablet. Use with SeaWave Software

36 Sound Analysis For analysing bat calls, we use 3 main graphical representations of sound waves: Oscillograms Displays time against sound pressure (amplitude) Power Spectrums Displays sound pressure (amplitude) against frequency Sonograms Displays time against frequency with amplitude represented by colour intensity

37 A = Oscillogram B = Power Spectrum C= Sonogram (or Spectrogram)

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40 Comparing pipistrelles Soprano pipistrelle 55kHz (peak between 51 and 56kHz). Common pipistrelle 45kHz (peak between 42 and 48kHz). Nathusius pipistrelle 39kHz (peak between 38 and 40kHz).

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42 Leisler s Bat Slow repetition rate Low frequency Tune in around 22-28kHz (higher frequencies when the bat is flying low or in clutter)

43 Myotis bats Myotis bats can be very difficult to distinguish in flight. Myotis bats change their echolocation calls depending on where they are flying.

44 MYOTIS Distinguishing Features End Frequency: Natterers have lowest end frequency of 15-28kHz End frequency of whiskered/brandts and Daubentons is similar 29-40kHz Start frequencies overlap BUT Natterer s tends to be highest (around 110kHz), whiskered lower (around 95kHz) and Daubenton s lower again (around 75kHz)

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46 Lesser horseshoe Echolocation calls unmistakeable at 110kHz, warbling sound on HD detector.

47 Soprano pipistrelle feeding buzz

48 Soprano pipistrelle feeding buzz

49 Books to Assist

50 Bat Analysis Software The following software applications do not offer automatic bat species identification, but they are very good at what they do. Which is to enable a user to view recorded ultrasounds. BatSound for Pettersson detectors, purchase license ( 348) BatScan for BatBox Duet (freq div) purchased for SeaWave Free, designed for Dodotronic microphones Soundchaser purchase license ( 580) Different software types are designed for use with different systems

51 Automatic Bat ID Software Bat call identification software is particularly difficult to produce well. There is a lot of work required, to make an effective product. The myriad of special algorithms required alone, can be overwhelming. It's not easy to find a well-executed, robust, and easy-to-use package and as a consequence it is never cheap!

52 Kaleidoscope Auto ID is intended for use in analyzing recordings of single bats in free flight, low clutter environments. Recordings of roost emergence, multiple bats, captive bats, bats in high-clutter environments or bat social calls are not suitable for Auto ID and results may not be accurate.

53 71% Brandt's bat Kaleidoscope 67% Daubenton's bat 87% Natterer's bat 60% Leisler s bat 91% Nathusius's pipistrelle 96% Common pipistrelle 96% Soprano pipistrelle 79% Brown long eared 91% Lesser horseshoe

54 Bat Classify & Bat Explorer Follow instructions on how to download this. This is of limited use at the moment but will be further developed. Download this free software if you do not have your own bat analysis software. Download the most up-to-date version NB please learn how to use bat analysis software before using Bat Classify.

55 Bat Classify Setting the Parameters Echolocation calls must be recorded in WAV sound files. Developed for use with Pettersson D240x and D500x units. Made compatible with EcoObs Batcorder, Elekon Batlogger, Batbox Griffin and Wildlife Acoustics Units. Software was designed for woodland bat species primarily. Software extracts all but the weakest calls and identifies the species likely to be present. Only Time Expansion and Direct Sampling calls can be used for analysis. Heterodyne and Frequency Division calls can not be used. Direct Sampling files should be short i.e. 1-3 seconds long

56 Bat Classify Setting the Parameters The software identifies each call and calculates the overall probability of each species being present based on all calls being analysed (Call-averaging). Results for each call segment is provided in an Excel File for review. The output file provides an estimate of the probability of occurrence in each file of each species. Probability ranges from 0 to 1 Precision is the proportion of bats calls that the software has identified to a species and identified it correctly. Recall is the proportion of available recordings of that species the software retrieves from the recording in order to identify it % is the measure to be used in order to accept for a species identification.

57 Species N F1 Precision Recall Barbastella barbastellus Myotis alcathoe Myotis bechsteinii Myotis daubentonii Myotis mystacinus / brandtii Myotis nattereri Noctule, serotine, Leisler s Pipistrellus pipistrellus Pipistrellus pygmaeus Plecotus auritus Rhinolophus ferrumequinum Rhinolophus hipposideros

58 Bat Classify Setting the Parameters The package is small and easily transferred from user to user and needs no installation. It is a stand-alone package and does not need commercial software to prepare calls for analysis. It is freely available. The source code is available for further development. If the results are interpreted with common sense and a basic knowledge of bat echolocation call structure then errors should be few.

59 FileName Bbar Malc Mbe c Mbra Mmy Mda s u Mnat NSL Paur Ppip Ppyg Rfer Rhip _ BLE _ Leis _ BLE&CP _ Pips _ My _ My_Natt _ SocCalls-Confusing

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