Social Calls of the Bats of Britain and Ireland

Social Calls of the Bats of Britain and Ireland

Neil Middleton

Andrew Froud

Keith French

Pelagic Publishing | www.pelagicpublishing.com

Published by Pelagic Publishing
www.pelagicpublishing.com
PO Box 725, Exeter EX1 9QU

Social Calls of the Bats of Britain and Ireland

ISBN 978-1-907807-97-8 (Pbk)

ISBN 978-1-78427-000-1 (ePub)

ISBN 978-1-78427-001-8 (Mobi)

ISBN 978-1-78427-002-5 (PDF)

Copyright © 2014 Neil Middleton, Andrew Froud and Keith French

This book should be quoted as Middleton, N., Froud, A. and French, K. (2014) Social Calls of the Bats of Britain and Ireland. Exeter: Pelagic Publishing.

All rights reserved. No part of this document may be produced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without prior permission from the publisher. While every effort has been made in the preparation of this book to ensure the accuracy of the information presented, the information contained in this book is sold without warranty, either express or implied. Neither the authors, nor Pelagic Publishing, its agents and distributors will be held liable for any damage or loss caused or alleged to be caused directly or indirectly by this book.

British Library Cataloguing in Publication Data

A catalogue record for this book is available from the British Library.

Cover image: Brown long-eared bats in bat box. Photograph by Derek Smith.

Contents

Foreword

Preface

Acknowledgements

About the authors

1.  An Overview of Bats within Britain and Ireland

2.  Introducing Bat Social Calls

3.  Classification of Social Calls

4.  Analysis of Social Calls

5.  Considerations in Survey Design

6.  Species Groups

Rhinolophus

Myotis

Nyctalus

Vespertilio

Pipistrellus

Eptesicus

Plecotus

Barbastella

Appendix: Downloadable Track List

Bibliography

References

Index

Foreword

It is common knowledge that bats live in colonies. In some species these colonies may number several thousand individuals. Animals that live a colonial life do so because the advantages of living together exceed the disadvantages of not doing so. Colonial life provides the advantage of knowledge sharing – where to find food; how to find mates; avoiding danger or warning others of potential harm – all of which are crucial for a species survival. And the means whereby this is undertaken? The answer is of course very much dependent on the species concerned and may involve communication through scent, movement, touch, audible noises or, in the case of bats, sound in the audible and ultrasonic spectrum.

High-pitched ultrasonic sounds are energetically expensive to produce and most bat species emit them when they require a detailed sonic picture of their environment (echolocation). When sound is needed and such detail is not required, the sound produced may be of lower frequencies. Many sounds produced by bats when not commuting or foraging are often lower in frequency than the species’ echolocation calls. It is conjecture that these ‘other sounds’ are all for purposes such as communication, but it is a reasonable assumption given their colonial lifestyle. Such sounds are often grouped together and termed ‘social calls’, although for many their precise purpose is something we can only guess at.

Neil, Andrew and Keith have produced a thoroughly researched book on this little understood and little explored subject, and have made recordings available to us, graphically, electronically and audibly. Their painstaking work of collating existing knowledge, in collecting, categorising and interpreting as many as possible of these non-hunting/non-commuting calls, is an important contribution to our bat survey and impact assessment armoury. Many species groups have vocalisations that are unique to them and an increased understanding of these sounds and their sonograms will improve our ability to identify bat species and interpret their behaviour. As consultants we are continually seeking ways of improving our ability to assess impacts and thus design appropriate mitigation. A better understanding of what bats are doing by surveying the places that they are doing it in, would go a long way to achieving this. Recording of social calls and an improved ability to interpret them could be the key!

In summary this is an important new work which will take our understanding of bats within Britain and Ireland, and therefore the techniques we use to conserve them, to a whole new level. I hope that this work will educate, inspire and encourage further research into this little understood and fascinating subject.

Dr Sandie Sowler MCIEEM
14th March 2014

Preface

Social calls relating to bats is an area about which relatively little is known, with continued research still required in order to verify what is already thought to be understood, and explore further our knowledge and understanding of this subject. During recent years when we have delivered this subject at training events we have been asked to explain the value of studying bat social calls. In short, they are becoming increasingly recognised as a good aid to identification, as in many respects they appear to be species-specific, as well as being indicative of bat-related behaviour (e.g. territorial behaviour of males during the mating season). In this day and age, when the gathering and interpretation of bat echolocation data are used as matter of course during research, conservation and consultancy work, it seems a logical progression to build momentum within mainstream bat-related work behind the subject of social calls.

This book summarises much of what is understood so far about social calls relating to the bat species occurring within Britain and Ireland. The authors and contributors have collected calls from throughout Europe, and it is anticipated that the material provided will be of benefit to people carrying out bat studies, at whatever level or for whatever purpose, and also encourage others to carry out further research. Social calls are fascinating to listen to: they are after all produced with listeners in mind (other bats). As such, to produce this work without the reader also having the opportunity to become a listener, and therefore fully appreciate the sounds produced, would have been falling well short of what could be achieved. Hence the rationale behind the accompanying downloadable sound files. These are there for you to explore either with or without the use of bat sound-related analysis software.

The material produced here will not give all the definitive answers relating to the subject. It is a complex area of study, which still, relatively speaking, requires a greater level of understanding. What we are seeking to do is pull together a lot of the information that currently exists, with the anticipation that over the next decade or so further research will increase knowledge and confidence. So please do not feel that you should read this book with a view to knowing everything there is to know by the end of it. In many respects there are still far more questions than there are answers (not an uncommon concept for those familiar with bats!). For the time being, please regard this piece of work as a source of reference and a collection of material, blended with our own experiences and thoughts, with the aspiration of creating intrigue and inspiring others to further the understanding of this fascinating subject.

Acknowledgements

The idea for this book was born out of the frustration of not having anything that was easily accessible to reference our own findings against. As the number of social calls encountered and the time spent analysing them increased, so did the need to reference what had been found. Talking to people interested in bats and presenting our findings to interested groups prompted a lot of debate as to why we were not delivering such an important subject to a wider audience. Our initial feelings of inadequacy were dispelled by the support and encouragement we have received on the journey, and this work could not have been produced without it. To everyone that has contributed to, enquired about or promoted what we were doing we owe a huge debt of thanks. In many instances material obtained by ourselves or contributed by others has not been included; however we feel it is important to acknowledge that all the material sent to us has been of great assistance to our overall understanding of this subject. There are many more examples that we could have used, and certainly some areas that we could have expanded upon more than we have (e.g. calls within maternity roosts). There comes a point, however, when the time and space available need to be considered, and all of that in conjunction with what the overall objectives of the project at the outset were.

We would like to thank and acknowledge the following people and organisations who have all contributed towards the finished work:

A special thanks to Derek Smith for allowing us to use his excellent photographs, including the front cover, and also to Sandie Sowler for providing the foreword and for being such a strong supporter and ambassador of what we were seeking to achieve. Sandie Sowler also, and Sue Swift, who gave up their time to review a near final draft of the work and provide their valuable feedback which helped to improve upon the final version. Laura Davis and Aileen Hendry, both of whom have supported the project throughout, and have given valued encouragement and feedback, as well as their thorough proofreading skills. Laura Davis also for providing the picture supporting the Pipistrellus species profiles, as well as Laurie Campbell and the National Trust for Scotland Ranger Service for the use of their pictures. Nigel Massen and Thea Watson of Pelagic Publishing, for their continued support and professional expertise throughout the final months leading to publication.

Tania Percy-Bell, Paul McNie, Amelia Hodnett, Andrew Hargreaves, Erika Dahlberg and Will Woodrow for their greatly appreciated support and time during the project. Sophie Punteney for statistical support, as well as assisting with the collection and analysis of calls. Sabine Schramm and Heather Ream for their assistance in the translation of foreign papers.

Lars Pettersson (Pettersson Elektronik, Sweden) for his support in our use of ‘BatSound’ software to generate many of the figures contained within the work, and for facilitating others to provide us with some of the calls we obtained from Scandinavian contributors. The Bat Conservation Trust (in particular Lisa Worledge and Anne Youngman) for promoting our work throughout the wider bat community, which resulted in many expressions of interest and contributions of calls. To the following organisations who assisted and supported the project: Cheddar Gorge & Caves; City of London Corporation (Epping Forest); Code 7 Consulting; Echoes Ecology Ltd; National Trust (Crom Estate and Lodge Park & Sherborne Estate); National Trust for Scotland (Threave Estate, Culzean Castle & Country Park, Hill of Tarvit, Ben Lomond, Brodick Country Park & Goatfell and Falkland Palace & Garden); Natural England; Scottish Natural Heritage; Stratton Deanery; Wildlife Provencale.

Finally with regards to providing considerable assistance in so many ways, including the provision of research papers, providing call contributions (whether making the final cut or not), arranging site access, and for general support and encouragement to the project we would especially like to thank all of the following: Elaine Anderson; Maggie Andrews; Kate Barlow; Mark Beard; Kathrin Bogelsack; Heather Campbell; Peter Cowling; Sarah Cox; Richard Crompton; Pieterjan Dhont; James Faulconbridge; Maurice Febry; Adam Fitchet; Joanna Furmankiewicz; Mike Glyde; Corinna Goeckeritz; Rhiannon Hatfield; Les Hatton; Soeren Hedal; Phillip Heels; Jon Hill; Colleen Hope; Paul Hope; Dave Hunter; Kjell Isaksen; Jackie Kemp; Jeroen van der Kooij; Danielle Linton; Heather Lowther; Lindsay Mackinlay; Roger Martindale; Phil May; Tore Christian Michaelsen; Aaron Middleton; Audrey Middleton; Stephanie Murphy; Ebbe Nyfors; Claire Parnwell; Steve Parnwell; Jools Partridge; David Patterson; Phil Riddett; Mike Robinson; Steven Roe; Jens Rydell; Harriet Safe; Amy Sneap; Rev. Robert Thewsey; Paul Wagstaffe; Nick Woods; David Woolley and Maja Zagmajster.

About the Authors

 

A library of downloadable bat calls (identified in the book with a symbol) is available to listen to in conjunction with the text.

Go to www.pelagicpublishing.com/social-calls-library.html to download the tracks, using reader access code SCB8F59K. See the Appendix for a list of all of the downloadable bat calls referred to in the book.

CHAPTER 1

An Overview of Bats within Britain and Ireland

Much has been written about the bat species occurring within Britain and Ireland, and it is not the intention here to reproduce what is easily accessible elsewhere. However, it is useful to cover a small number of more general areas relating to bats in order that the reader can relate the main subject matter of this book (i.e. social calls) to the species present in the area and their typical seasonal behaviours.

1.1  Species diversity

Within Britain and Ireland there are 17 species of bat regarded as being resident and breeding, represented by two families, comprising seven genera (see Table 1.1). In addition to these, other bat species have occasionally been found to be present, though these are thought to be occurring either purely as migrants or incidentally as vagrants (i.e. population not established and/or breeding not considered to be taking place). Throughout the world there are many families of bats; however, only two are known to be capable of true hibernation (Ransome, 1990; Altringham, 2003). Not surprisingly, due to our temperate climate producing much colder conditions in winter and hence less insect food availability, all bats occurring within Britain and Ireland belong to these two families.

1.2  Life cycles

In order to help understand the social aspects of bats it is useful to consider their life cycles. Table 1.2 describes the typical annual life cycle of the species which are resident within Britain and Ireland. Bear in mind that the information shown is of a general nature and therefore not species or location specific. There is considerable variation among species regarding their behaviours and differences occurring, within species groups, geographically within the area covered by this book. Furthermore, changing and unpredictable weather patterns are almost certainly having an impact upon bat behaviour.

1.3  Roosting behaviour

Throughout the year bats use a variety of different roosting locations (including alternatives) taking account of their specific needs, the season, unseasonable changes in weather conditions, disturbance and depending upon whether they are male or female. Table 1.3 provides examples of the different roost types that are typical for most of the bat species occurring in Britain and Ireland. Depending upon the species involved, a number of these roosting requirements could potentially occur within a single location. In reality, however, more often they tend to be separate from each other, either in the same locality, or for some species further away.

1.4  Commuting and foraging

All of the bat species occurring within Britain and Ireland use echolocation in order to help them commute and forage. Echolocation is a sophisticated system through which bats build up a sound picture of their surroundings, by producing a rapid repetition of a series of high-frequency pulses ( 1.1), and then listening for the returning echoes. Using this system a bat is able to establish its proximity to features, locate prey and navigate to and from roosting locations and foraging sites. The information that bats seek to gather as a result of echolocation is greatly aided, especially for some of our smaller species, by the presence of linear features along which bats can navigate and orientate themselves in the dark (Russ and Montgomery, 2002; Downs and Racey, 2006). Furthermore, these linear features provide a degree of protection from poor weather conditions and potential predation, and can also act as valuable foraging locations in their own right. The following are a small number of examples of features used by bats whilst commuting:

• Tree lines
• Hedgerows
• Waterways (e.g. rivers/canals/lake shores)
• Woodland tracks and rides

Within Britain and Ireland, all of the bat species present are insectivorous and require large quantities of invertebrate prey (insects and, in some cases, arachnids), in order to fuel their high metabolisms. As such it is important that good healthy invertebrate populations thrive within the environment in which bats are present, and that these food resources are accessible to bats throughout their periods of activity.

1.5  Habitat use model

To summarise, in order to interact naturally with their surroundings, establish viable populations and indeed survive, bats need suitable roosting habitat, foraging locations and additional features that can assist with orientation in the dark, thus allowing them to navigate successfully between roosts and foraging areas. Taking account of all of this, the behaviours for many of the bat species occurring within Britain and Ireland can be described as shown in Figure 1.1.