New survey improves our understanding of bats in southern Scotland

Support from 275 volunteers – in one of the largest-ever volunteer-based surveys in Scotland – is giving a clearer picture of bat populations in Southern Scotland.

An encouraging finding was that Leisler’s and noctule bats were found to be more abundant than previously thought, although they are still among the five scarcest species of bat in Scotland.

A report commissioned by Scottish Natural Heritage (SNH) demonstrates the power of the volunteers in helping to better understand the distribution of rare and vulnerable species. Coordinated on behalf of SNH by the British Trust for Ornithology (BTO), the survey was carried out across southern Scotland and had huge support from enthusiastic volunteers throughout the area collecting data in the summer of 2016.

Collecting the data

Volunteers used bat detectors borrowed from 16 bat monitoring centres set up for the purpose. Detectors were set in position for between one and three nights and left to record any activity overnight. The National Trust for Scotland, RSPB Scotland and Forestry Commission Scotland also contributed, using multiple bat detectors on their properties for extended periods. Researchers analysed the data emerging from this and were able to update current population estimates and distributions across the area.

The collective effort generated over 1,500 complete nights of recording in just under 1,500 different recording locations. Almost 670,000 recordings were collected which included just under 400,000 bat recordings.  In total, the survey collected data across 715 one-kilometre squares in southern Scotland – an area of more than 20,000 km² – making it one of the largest-scale volunteer-based surveys in the country.

The study focused on the distribution and abundance of three bat species – Leisler’s bat, noctule and Nathusius’ pipistrelle – because their preferred habitat and hunting styles make them particularly vulnerable to wind farms. It was found that the previous population estimate of about 250 bats per species can now be increased to thousands.

Bats are notoriously difficult to count. They are only active at night and are very quick and mobile. It’s impossible to identify individuals from their sound so it’s easy to mistakenly count a bat more than once. Because of this, exact counts are impossible, but broad estimates can be based on bat calls and activity.

Southern Scotland has one of the highest densities of wind farms in the country. The study has produced detailed data and mapping which will be invaluable in assisting decisions in the region, including assessing future onshore wind energy construction.

The power of volunteers

Sally Thomas, Director of Policy and Advice at Scottish Natural Heritage said, “This survey shows the power which volunteers have in helping us to better understand little-known species. We had a tremendous response from the small army of volunteer citizen scientists who helped collect the survey data, and we’d like to express our thanks to them all for their support. The information they have collected will certainly help us and others to make better-informed decisions on future developments.”

Stuart Newson of the British Trust for Ornithology added, “There is a real need for higher-quality data of this type to inform our understanding of bat distribution and activity if we are to make good decisions for bats across a range of issues. As a minimum standard, researchers working on bats should prioritise the collection and use of distributional data with consideration of the underlying survey design and representativeness of the data collected.  This can be achieved most cost-effectively by working with the public to develop large-scale acoustic monitoring schemes.”

Read the full report

For more information on bats, visit the Bat Conservation Trust website.

View the distribution of the bats as shown on the NBN Atlas and NBN Atlas Scotland

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