Magenta Detector

Magenta bat detectors are heterodyne detectors that allow you listen to the bats echolocations calls as they fly around you at night. Unlike the SM2 and Anabat Express detectors they do not record any of the bat calls, and so we do not recommend using the Magenta as a sole bat detector. The Magenta bat detector needs to be tuned so that you can hear the bat calls, see diagram below:


Turn the detector on until you can hear a quiet hissing sound, check the torch is not on (unless you need it) and turn the frequency dial until the display reads around 45kHz.

You are now ready to hear the bats echolocation calls. Different species of bats call at different peak frequencies, they also use different repetition rates and rhythms. When you are listening to a bat you need to tune the detector up and down until you hear the deepest note, this is not necessarily the loudest sound, often it can be quite quiet.

Pipistrelle species have a fast repetition rate with an irregular rhythm; common pipistrelle have a peak frequency around 45kHz and soprano pipistrelle have their peak frequency around 55kHz. Their calls ahve been described as sounding like a wet slap!

Noctules, our largest bats, have a slow repetition rate with a more regular chip-chop pattern , their calls are loud and relatively slow with a peak around 20-22kHz.

Myotis species bats do not have a peak frequency to their calls, but make a fast regular clicking sound, these bats do not fly until it is almost dark, making them harder to detect.

If you are only using a Magenta then it is important that you make a note of the following information:


Time when survey started and ended

Where you were

A grid reference would be best; a good website for finding a grid reference is If you put in your location, ie Loftus, this will let you move the cursor over the map to where you are and give you the six figure grid ref, ie NZ714184. If you are unable to do this, please make a note of the postcode and address and a description of where you walked.

Ambient temperature when survey started and ended

You can get this from a mobile phone or checking up on


Cloud cover, rain and wind direction and approximate strength

Level of bat activity

Make a note of how much bat activity there was, for example the time of your first bat, where there was a lot of bat activity, the number of bat passes (individual bat calls) you detected or where you recorded different species of bats (if you are able to tell them apart).

Download the quick start guide

Download Recording Form