07.08.2012

Holy bat detector! Ecologists develop first Europe-wide bat ID tool

A small colony of greater mouse-eared bats (Myotis myotis)in  Rodersdorf, Switzerland. Photo WSL / Martin Obrist

Press release of the BRITISH ECOLOGICAL SOCIETY

Just as differences in song can be used to distinguish one bird species from another, the pips and squeaks bats use to find prey can be used to identify different species of bat. Now, for the first time, ecologists have developed a Europe-wide tool capable of identifying bats from their echolocation calls.

The new free online tool – iBatsID – will be a major boost to conserving bats, whose numbers have declined significantly across Europe over the past 50 years. Details are published today in the British Ecological Society's Journal of Applied Ecology.

Working with an international team of ecologists, lead author and PhD student Charlotte Walters from the Zoological Society of London (ZSL) selected 1,350 calls of 34 different European bat species from EchoBank, a global echolocation library of more than 200,000 bat calls.

The calls were then analysed to find out which characteristics were most useful in distinguishing different bat species. According to Walters: “Lots of different measurements can be taken from an echolocation call, such as its maximum and minimum frequency, how quickly the frequency changes during the call, and how long the call lasts, but we didn’t know which of these measurements are most useful for telling different species' calls apart.”

The 12 most useful call parameters were then used to train artificial neural networks to produce the new identification tool, iBatsID, which can identify 34 different bat species across the whole of Europe. Most species can be identified correctly more than 80% of the time, although accuracy varies because some species are much harder to identify than others. “iBatsID can identify 83-98% of calls from pipistrelle species correctly, but some species such as those in the Myotis genus are really hard to tell apart and even with iBatsID we can still only identify 49-81% of Myotis calls correctly,” she explains.

iBatsID should have a major impact on European bat conservation, which until now has been hampered by the absence of a standardised, objective and continent-scale identification tool. According to Professor Kate Jones, another of the paper's authors and chair of the Bat Conservation Trust: “Acoustic methods are really useful for surveying and monitoring bats, but without using the same identification methods everywhere, we can't form reliable conclusions about how bat populations are doing and whether their distributions are changing. Because many bats migrate between different European countries, we need to monitor bats at a European, as well as at country, scale. In iBatsID, we now have a free, online tool that works anywhere in Europe.”

Bat populations have declined significantly across Europe since the middle of the 20th century. As a result, all bats are now protected through the EU Habitats Directive. Bats face many pressures, including loss of roosting sites in trees and buildings; loss of feeding habitats in woodlands, meadows, parks and gardens; falling insect numbers; and habitat fragmentation resulting in the loss of green corridors such as hedges that provide connectivity in the landscape.

As well as providing vital ecosystem services, such as pollinating plants and controlling insect pests, bats are important indicators of biodiversity. “Bats are very sensitive to changes in their environment, so if bat populations are declining, we know that something bad is going on in their environment. Monitoring bats can therefore give us a good idea of what is going on with biodiversity in general,” Walters adds.

Main author of the study ist Charlotte Walters, Institute of Zoology, Zoological Society of London, tel: 07841 875606, email: charlotte.walters@ucl.ac.uk.

WSL contributions came from Dr. Martin K. Obrist (Birmensdorf) an d Dr. Thomas Sattler (Bellinzona).

Contact at WSL

• Martin Obrist
  

Notes for editors

A continental-scale tool for acoustic identification of European bats

by Charlotte L. Walters, Robin Freeman, Alanna Collen, Christian Dietz, M. Brock Fenton, Gareth Jones,    Martin K. Obrist, Sébastien J. Puechmaille, Thomas Sattler, Björn M. Siemers, Stuart Parsons, Kate E. Jones

Bats make up a fifth of all mammal species and occur in all areas of the world except for the Arctic, Antarctic and a few oceanic islands. Many bats use echolocation for orientation and prey detection. Different bat species have evolved different call structures, and individual calls can also vary depending on what the bat is trying to do: while commuting and searching for prey, bats use “search phase” calls, with calls becoming shorter and more rapid as they zero in on prey. Some species' calls also vary across their geographic range, with bats having different “dialects” in different parts of Europe.

This study was funded by NERC, the Leverhulme Trust, the Darwin Initiative and the University of Auckland. The study team came from the Zoological Society of London, the Bat Conservation Trust, University of Kent, University College London, Microsoft Research, Cambridge, University of Western Ontario, University of Bristol, Swiss Federal Institute for Forest, Snow and Landscape Research WSL, University College Dublin, Max Planck Institute for Ornithology, Groupe Chiroptères de Midi-Pyrénées, University of Ulm and University of Auckland.

The Journal of Applied Ecology is published by Wiley-Blackwell for the British Ecological Society. Contents lists are available at www.journalofappliedecology.org.

The British Ecological Society is a learned society, a registered charity and a company limited by guarantee. Established in 1913 by academics to promote and foster the study of ecology in its widest sense, the Society has 4,000 members in the UK and abroad. Further information is available at www.britishecologicalsociety.org.

ZSL. Founded in 1826, the Zoological Society of London (ZSL) is an international scientific, conservation and educational charity: the key role is the conservation of animals and their habitats. The Society runs ZSL London Zoo and ZSL Whipsnade Zoo, carries out scientific research in the Institute of Zoology and is actively involved in field conservation in more than 50 countries worldwide. For further information please visit www.zsl.org.

Copies of the paper, photographs and audio clips of bat calls are available from Becky Allen, British Ecological Society Press Officer, tel: +44 (0)1223 570016, mob: +44 (0)7949 804317, email: beckyallen@ntlworld.com