Change is in the air . . .

Transition to our new website!


BAT125FG2About transect surveys . . .

A “transect” is simply an arbitrary line throughout a habitat where continuous or point-count measurements of species occupancy can be conducted. Using bat detectors on transects allow us to estimate and monitor bat abundance and/or species abundance at single locations and multiple locations throughout a habitat. By moving continuously through a habitat and recording bat calls we can be assured that each call recorded represents a different individual, since it is unlikely in the extreme that a single bat will be following us along the entire transect, or portions of a transect.

By stopping periodically on our transect line and monitoring for a pre-determined amount of time, we can cover a lot of ground and perhaps intercept bats and record longer file sequences that could be more useful for species ID.

The tools we might select to accomplish this mission is a little different than a straightforward active or passive detector. We want a high quality microphone system as always to maximize the chances for species ID. Because the microphone is often moving during the survey, an omnidirectional mic response may be desirable to record longer call sequences as the bat remains in the "bubble" of moving reception. A live display is useful to engage users on what otherwise may be a tedious, uneventful monitoring session. Finally, the whole point of transects is to log bat activity over a large geographic area, so some sort of software solution for visualizing transect data is helpful.


Why the AR125FG?

  • The omnidirectional-like coverage of this microphone is ideal for moving transects and captures significantly more pulses in files than directional microphones and lower quality omni-directional mics.
  • The AR125-FG is controlled via BAT's SPECT’R software which performs live view of incoming bat calls and recording. It is designed for field collection and it is capable of operating up to any four BAT USB microphones from a single laptop.
  • The BAT miniMic is a less expensive version of the AR125-FG. The AR125-FG is housed in a robust weatherproof housing more appropriate for inclement weather. It is also tested to have a noticeably lower noise floor than the miniMic.
  • Orient this microphone vertically with the element on the top to minimize moisture in the cable port. Billed as omnidirectional, raise this microphone as far as possible from all obstructions (~12'+ above ground) and extend it into the airspace you intend to monitor.
  • Power consumption is irrelevant for typical mobile transects working from and powered by vehicles. We like the ability to run the live view of Spect'r/AR125FG in one window on a vehicle mounted laptop, and also run our GPS-enabled mapping software of choice in another window, such as Terrain Navigator or Google Earth, etc., although smartphone tracking apps are reducing the need for a laptop-based map solution. For walking transects, the Spect'r/AR125FG combo on a tablet will run plenty long enough for survey typically lasting only a couple hours, so again power consumption is not an issue.


item4Why the Transect app?

  • Written by bat biologists solving a real workflow problem of visualizing transect data.
  • Not locked to a particular brand of detector. Any detector generating a time stamped event + any GPX log file produced by a GPS or smartphone app generates a file viewable in Google Earth.
  • Works with Anabat/BAT/SonoBat/Wildlife Acoustics as well as a number of European detector file formats.


What do you need?

  • BAT AR125FG
  • 30' USB Active Extension Cable
  • mist net poles or telescoping pole appropriate to fix the mic about 10' above ground, certainly 3' or more away from the roof of the vehicle
  • A Win XP or higher tablet/netbook/laptop or Mac running Parallels
  • Any GPS/smartphone that outputs a GPX track log
  • Bat ID software to distill data down to just bat calls, see our recommendation here.
  • Transect app to merge bat call data with your GPX log
  • Optional, but suggested- mapping software with your proposed transects highlighted, such as Terrain Navigator, Google Earth, etc.





BCM's Comparison Chart for Acoustic Transects
Any detector can be used for acoustic transects as long as it generates a time stamped file.
It does NOT need a built-in GPS (see Transect software above). Most modern Passive Detectors are perfectly suited for transects, but the detectors on this chart simply feature a real time display that is "fun" to watch while conducting your survey and also supports GPS intergration.

This chart does not mean to suggest other detectors are not suitable for mobile transects... most are!


A note about automatic classification of bat calls: Some manufacturers are incorporating species ID into their devices. While this is an amazingly fun thing to watch in real time. the reality is often the species ID can be flat out wrong. If you as a user choose to append automatically classified names to the data and/or maps, you and anyone that data is shared with should be prepared to accept some degree of error. For professional use, BCM strongly suggests all auto-classifications be expertly reviewed using professional level software before accepting any data results.




See also: BCM's top pick for:

Passive Monitoring

Active Monitoring

Mobile Transects

Automated + Manual Bat Call ID Software

BCM's Top Recommendation for Mobile Transects:

BAT AR125 FG + Transect

BAT MiniMic

Conceived at the April 1, 2013 Western Bat Working Group Meeting, BCM received the first two prototype miniMic devices just a few weeks later in time for a full summer of testing. The D500X is a USB driven full spectrum ultrasound microphone intended for live view active monitoring, mobile transects, and short term unattended (passive) monitoring of bat and other high frequency animal calls. The miniMIC is specifically designed for applications such as bat recording and vocalization analysis where wide spatial coverage and a wide ultrasonic frequency range are desired. It employs low noise circuitry along with 16-bit digital converters to achieve high sensitivity along with a large dynamic range. It is capable of detecting bats at a distances up to one hundred and forty feet.

General MiniMIC Features:

MiniMIC is better suited for: