Monday, 10 July 2017

An update on the bat project

The project has now been running from April and we have been out on 13 nights. Unfortunately due to poor weather many of our surveys have been cancelled as we can only go out when there's no rain or wind. However, in the past couple of weeks the bats have been out in force! At the start of April many of the nights were only just above 10*c, windy, and there was only a few passing bats but now that its getting warmer we are getting many more feeding above our heads.

The noises we are picking up are the bat's echolocation. This is when the bats emit sounds (usually at high frequencies undetectable to humans) and use the echoes from nearby objects to essentially "see" (through hearing) their surroundings. They use this to navigate the woodland but also to locate insects to feed on.

Emily and Alison recording and counting bat calls and writing down times.
We have picked up at least 3 distinctive types of calls so far. We believe they could be the feeding calls of a Pipistrelle and a type of Myotis bat as well as some communication calls (high pitch squeak sounds).

The feeding calls are a series of clicks and, due to the Doppler effect, we can tell when they're flying past as it get louder then quieter (like an ambulance or racecar). When bats are 'calling' to fly around objects their calls are spaced apart but when they are feeding these calls are closer together.
When the bats get even closer to the prey, the noise turns in to a raspberry/fart noise which when they make lots of rapid calls to give them a better idea of where the insect is. Their communication calls are quick high pitch squeaks that are very distinctive from the feeding calls. Check out this video for some of the calls we are hearing:  BAT VIDEO

We believe that many bats in the surrounding area, such as Much Wenlock, come to the woods to feed, and could be using the Blakeway hollow path like a corridor into the denser woodland as this is where the highest amount of bats have been heard.