Amphibian Survey and
Monitoring Handbook
John W. Wilkinson
Pelagic Publishing | www.pelagicpublishing.com
Published by Pelagic Publishing
www.pelagicpublishing.com
PO Box 725, Exeter EX1 9QU, UK
Amphibian Survey and Monitoring Handbook
ISBN 9781784270032 (Pbk)
ISBN 9781784270049 (Hbk)
ISBN 9781784270056 (ePub)
ISBN 9781784270063 (Mobi)
ISBN 9781784270742 (PDF)
Copyright © 2015 John W. Wilkinson
This book should be cited as Wilkinson, John W. (2015) Amphibian Survey and Monitoring Handbook. Exeter: Pelagic Publishing, UK.
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 author, 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 images, top left: parsley frog (Pelodytes punctatus), Mark Barber; mid left: dip-netting, John W. Wilkinson; bottom left: western common toad (Bufo spinosus), John W. Wilkinson; top right: ©iStock.com/Kalawin; centre: Morogoro tree toad (Nectophrynoides viviparus), John W. Wilkinson; centre bottom: palmate newt (Lissotriton helveticus), John W. Wilkinson; bottom right: fire salamander (Salamandra salamandra), John W. Wilkinson.
Typeset by Saxon Graphics Ltd, Derby
For my Mom, Wendy, who became very good at
rearing Dendrobates truncatus and could find room
for 5,000 toad tadpoles at only a moment’s notice …
List of figures
List of tables
Foreword
Preface
Acknowledgements
1Introducing amphibians
1.1 Amphibian diversity
1.2 Order Anura (frogs and toads)
1.3 Order Caudata (newts and salamanders)
1.4 Order Gymnophonia (caecilians)
2Before you start surveying
2.1 Types of survey
2.2 Survey and monitoring programmes
2.3 Survey aims and resources
2.4 Collecting survey data
2.5 Survey permissions and licences
2.6 Health and safety, and biosecurity
2.7 Handling amphibians
3During your survey: amphibian survey methods
3.1 Amphibian surveys in aquatic habitats
3.2 Amphibian surveys in terrestrial habitats
3.3 What other data should you collect?
4After your survey
4.1 Arranging your data for analysis
4.2 Setting out your survey report
4.3 Who needs to see your data and read your report?
4.4 Taking amphibian studies further
5Resources to help you
5.1 Example survey forms
5.2 Risk Assessments
5.3 Guides to amphibian identification and ecology
5.4 Other useful textbooks
5.5 Equipment suppliers
5.6 Amphibian study and conservation organizations and societies
References
Glossary
Index
Figure 1.1 | The archetypal anurans are frogs like this Epirus water frog (Pelophylax epeiroticus). |
Figure 1.2 | Fairly typical (in shape at least) for an anuran is the Morogoro tree toad (Nectophrynoides viviparus) from the Eastern Arc Mountains of Tanzania. |
Figure 1.3 | The palmate newt (Lissotriton helveticus) is a typical pond-breeding newt. |
Figure 1.4 | Plethodon cinereus is a widespread and variable lungless salamander from eastern North America. |
Figure 1.5 | Ichthyophis beddomei is a caecilian endemic to the Western Ghats of India. |
Figure 2.1 | Nitrile gloves in use during a survey. |
Figure 2.2 | Handling small caudates. |
Figure 2.3 | Handling a large anuran. |
Figure 2.4 | This caecilian (Grandisonia sechellensis) has been anaesthetized to have a buccal swab taken as part of a genetics study on Seychelles herpetofauna. |
Figure 2.5 | Handling a small amphibian for taking measurements. |
Figure 3.1 | Preliminary survey visit sketch of Oakwood Park Pond. |
Figure 3.2 | Spotting newt eggs. |
Figure 3.3 | Newt eggs on folded grass. |
Figure 3.4 | Spawn clumps of the European common or grass frog (Rana temporaria). |
Figure 3.5 | A torchlight amphibian survey. |
Figure 3.6 | Night torching survey method. |
Figure 3.7 | Making and setting bottle traps. |
Figure 3.8 | Setting a bottle trap. |
Figure 3.9 | Bottle trap line. |
Figure 3.10 | Retrieving a bottle trap. |
Figure 3.11 | Mesh funnel (crayfish-type) trap in position on a newt survey. |
Figure 3.12 | Assembling and setting Ortmann-type traps. |
Figure 3.13 | Dip-netting in action. |
Figure 3.14 | An artificial egg mop ready for setting. |
Figure 3.15 | Surveying a large terrestrial (leaf litter) plot in the Seychelles. |
Figure 3.16 | Juvenile toads (Bufo spinosus) found sheltering under an established artificial refuge in Jersey, Channel Islands. |
Figure 3.17 | Your survey transects must be practical and achievable. |
Figure 3.18 | Diagrammatic representation of the start of a VES transect within an imaginary rectangular tube about 4 m wide and 2 m high. |
Figure 3.19 | A pitfall trap haul of toads (Rhinella crucifer) from a survey in Brazilian Atlantic forest. |
Figure 3.20 | Cross-sectional diagram of a pitfall trap in use with a drift fence. |
Figure 3.21 | Example arrangements of drift fences with pitfall traps. |
Figure 3.22 | Drift fence and pitfall trap array being used to sample herpetofauna in a dune system in Atlantic coastal Brazil. |
Figure 3.23 | Proprietary drift fencing staked in an extensive grid pattern. |
Figure 4.1 | A male great crested newt temporarily restrained in a clear plastic box (which formerly held a popular brand of chocolates) for photographing its belly pattern. |
Figure 5.1 | Example site information form. |
Figure 5.2 | Example recording sheet (individual amphibians). |
Figure 5.3 | Example recording scheme form. |
Table 2.1 | Essential survey information. |
Table 2.2 | Adding useful information to survey forms. |
Table 3.1 | Suggested environmental variables for amphibian surveys. |
Table 3.2 | Suggested habitat variables for amphibian surveys. |
Table 4.1 | Data showing adult amphibians recorded over four visits to Dewlands Common Pond in 2014. |
Table 4.2 | Some of the data from a fictitious amphibian survey of Oakwood Park Pond. |
Table 5.1 | Some examples of assessed risks associated with amphibian survey activities. |
Table 5.2 | Assessing overall level of risk, with examples of action needed. |
A gleam on water. Light illuminates the surface to reveal two long strings of dots like necklaces of black pearls. Under a hefty stone on the gently sloping bank, a natterjack huddles down to get warmth from the surrounding sand. Beyond the bank, females have burrowed below the sparse turf awaiting the call to spawn. Away on pastoral farmland, tadpoles of the common toad have struggled from their spawn entwined around vegetation in deep pond water.
You don’t need to go far to see such engaging creatures if you only stop to look, wait by a pond and see what happens. Return after dark with a good torch and see newts courting at the margins and, with luck, the great crested newt in full display: a waggling tail, a silver flash, a crest erect. But such fascinating creatures face a difficult future: humans drain the land, fill in ponds, build houses and intensify agriculture.
Bodies like Amphibian and Reptile Conservation aim to conserve amphibians not just for their own sake but because they are part of the intricate web of biodiversity, in which all creatures play a part and enrich the quality of our lives, if only briefly.
You can become involved and help amphibians. John Wilkinson details how to plan survey work, record and monitor the presence of species that will yield the information vital for conservation policy and practice. John’s lifelong experience and enthusiasm for amphibians shines through his book. So, read, enjoy, survey and thereby help give our amphibians a more secure future.
John Buckley
Amphibian Conservation Officer
Amphibian and Reptile Conservation
Boscombe 2015
By far the most effective way of conducting an amphibian survey would be to know from the start exactly what data you were going to generate and how you were going to use those data (having read every relevant publication and designed your survey protocols accordingly). Few of us, however, have that luxury for most of the time. The aim of this book is to set out the considerations and techniques needed for conducting amphibian surveys so that you will obtain data you can use. I have also used published amphibian survey studies as guiding examples and suggested further reading. With a little forethought, you can make your amphibian survey interesting, useful and effective in achieving its goals.
The Amphibian Survey and Monitoring Handbook is divided into three main chapters: covering before, during and after your survey. What questions do you need to ask before you start? How will you carry out the survey and what equipment will be needed? Having completed your survey, how will you arrange your data and what is the best way to tell everyone else what you’ve found out?
Having read this far you have probably started to ask some of these questions: good! Use the sections of this book to make checklists of the resources and techniques you will use throughout your survey. When planning any kind of study or survey project, I start with a long list of notes and things to do, some of which need to be ticked off near the start and others of which can be dealt with as the survey progresses. As you become familiar with surveying amphibians (or if you already have some experience), your lists become shorter as you acquire the skills and equipment required. Good planning (and some flexibility!) goes a long way towards making your amphibian survey successful.
As well as actual survey techniques, I have also included a section on handling amphibians. Believe it or not, I have in the past been asked to advise on ambitious and well-planned surveys of amphibians in remote parts of the world, by people who have never actually held a frog!
This book does not cover species identification, though the different groups of amphibians are discussed in the first section. It is, however, very important to have a good idea of the range of species you are likely to encounter during your survey, so refer to one of the many excellent national and regional amphibian guides now available (see Chapter 5). Also, though I haven’t covered in detail all possible studies involving amphibians, some of these are discussed in Chapter 4. A huge variety of investigations can be carried out, and perhaps your amphibian surveys will inspire you to look more deeply into the biology of these intriguing animals.
Most of my amphibian research and surveying has been carried out in the British Isles, where I live and work, so I have drawn on these experiences to populate the chapters of this book. I have, however, tried to include examples and illustrations from different parts of the world to illustrate important points. Many thousands of people around the world now conduct amphibian surveys, whether out of personal interest or for professional or academic reasons, and find it a fascinating and rewarding activity. I very much hope that you do too.
John W. Wilkinson, Dorset 2015
Thanks to Mark Barber, Trevor Beebee, John Buckley, Emma Douglas, Dorothy Driver, Matt Ellerbeck, Tony Flashman, Georgia French, Mark Gardener, Tony Gent, David Gower, Stuart Graham, Peter Hill, Jim Labisko, Brett Lewis, Simon Maddock, Liam Russell, David Sewell, Rick Sharp, Thomas Starnes, Ben Tapley, Moacir Tinoco and David W. Williams, who provided comments, ideas, photographs, information or advice for these pages. Last but not least, I thank Nigel Massen and Thea Watson of Pelagic Publishing for their help and patience! Without the help of all these people, this book would not have been possible.
Today’s amphibians are descended from the first terrestrial vertebrates that evolved from bony-finned fishes some 360 million years ago. A few tens of millions of years later, early amphibians gave rise to reptiles, and ultimately therefore to both birds and mammals. Your ancestors were amphibians!
The majority of amphibians develop from gelatinous eggs laid in water, which hatch into aquatic larvae (tadpoles or polliwogs) and gradually metamorphose into terrestrial juveniles resembling the adults. Many species, however, have evolved variations on this theme. Some salamanders, for example, reach sexual maturity in their larval form and never attain true adulthood, and some frogs produce eggs within which the tadpole stage takes place, hatching into fully formed froglets. Still others undergo the typical amphibian metamorphosis but remain aquatic throughout their lives. For a fuller overview of the diverse range of amphibian life histories, see Cloudsley-Thompson (1999), Halliday and Adler (2002) or Wells (2007).
Modern amphibians number more than 7,000 species in three orders (see below). This number is only a fraction of the diversity present when amphibians were the dominant terrestrial vertebrates during the Carboniferous and Permian periods, more than 300 million years ago.
Amphibians are now among the most threatened of vertebrate groups, with more than 30% of amphibian species falling into IUCN threat categories (Stuart et al., 2004). Though some amphibians are declining to extinction – many more than would be without the influence of humans (McCallum, 2007) – the number of known amphibian species is actually rising as a result of taxonomic research and advances in methods used for separating species (see Box 1.1 on page 7).
Many factors are contributing to global amphibian declines, including emerging diseases and pollution, but by far the most serious threats to amphibians are the loss and fragmentation of their habitats. The modern, human-dominated world is a hostile place for many amphibians, which have particular ecological needs, including, for example, the need to migrate between hibernation sites and breeding ponds. Despite this, many amphibian species persist and thrive alongside human activities where the features on which they depend are still present in the landscape. Often, it is habitat fragmentation and the rate of landscape-scale change that prevent amphibians from colonizing new habitats, such as urban ornamental and sustainable urban drainage system (SUDS) ponds (e.g. Gledhill and James, 2008). For more information on global amphibian declines, see the reviews by Beebee and Griffiths (2005), McCallum (2007), Hamer and McDonnell (2008) and Blaustein et al. (2011).
The fact that many amphibians, even familiar and widespread species such as the common toad (Bufo bufo) in Europe, are declining (Carrier and Beebee, 2003) is one of the factors driving the need for effective and informative surveys. Whether conducting a site species inventory or carrying out detailed monitoring of a single population, survey results provide invaluable information that can lead to better conservation decision making. Your surveys can therefore inform positive action that will help prevent further declines in these critical components of our ecosystems.
The anurans are the most diverse and numerous of the amphibians, with more than 6000 species in more than 50 families. The familiar frogs and toads are anurans, though the distinction between the two is an artificial one: anurans that jump and have smooth skin are referred to as ‘frogs’, and those with warty skin and a tendency to walk or hop are called ‘toads’. The midwife toads (genus Alytes) and fire-bellied toads (family Bombinatoridae) are more closely related to frogs than are the poison-dart frogs (Dendrobatidae) and treefrogs (Hylidae), which are allied to the true toads (Bufonidae).
Anurans lack tails and usually have a moist, scale-less skin that can be smooth or glandular and warty. Most species are also characterized by their prominent eyes, used for locating moving prey, and many species produce distinctive calls, most often as a way for the males to attract a mate. They breed, typically, in water (see Fig. 1.1), using external fertilization and laying eggs singly, in clumps or in strings, in a variety of aquatic situations from small, temporary puddles to large, permanent lakes. The jelly-covered eggs hatch into swimming larvae (tadpoles or polliwogs) that develop over days, weeks or (sometimes) years into smaller versions of their parents. Some of the many exceptions include the viviparous Nectophrynoides (see Fig. 1.2) and the Neotropical genus Eleutherodactylus. The eggs of the latter undergo direct development, hatching into fully formed froglets. Some species of anuran (e.g. the red-eyed treefrog, Agalychnis callidryas) deposit eggs on leaves over ponds or in other situations where the tadpoles can wriggle into the water when they hatch, reducing the risk of their eggs being eaten by predators. Other species, including members of the Dendrobatidae, reduce this risk by practising advanced parental care. Eggs are cared for and kept moist by one or both of the parents and the tadpoles are carried to suitable puddles or reservoirs of water in epiphytic plants to develop in relative safety. Some dendrobatids even produce unfertilized eggs that provide a regular source of nourishment for the growing tadpoles.
The order Caudata contains more than 600 species in 10 families. Though there are many fewer species than in the Anura, caudates nevertheless display a remarkably diverse range of life histories. Caudata includes the pond-breeding newts (see Fig. 1.3) of Europe, Asia and North America (family Salamandridae) but, again, the distinction between newts and salamanders is an artificial one based on their life histories. Many salamanders are more terrestrial than newts but equally others, such as the axolotl of Mexico (Ambystoma mexicanum) and members of the family Proteidae (including the olm, Proteus anguinus, of Europe), are paedomorphic, never leaving the water and never usually developing into an adult form. They retain their larval characteristics and breed, effectively, as tadpoles.
More than half of the species of caudate, however, belong to the family Plethodontidae. This family has a few species in Europe and many in the Americas, and is the only caudate family with many species in the Southern Hemisphere. The majority of this family are terrestrial (see Fig. 1.4), though some live aquatically, and quite a few small, Neotropical species have evolved to be arboreal, using direct development of their eggs to conduct their entire, tiny lives above ground. Plethodontid salamanders are lungless, obtaining all the oxygen they need through their skin.
Unlike anurans, all caudates have tails and a low-slung, lizard-like body pattern. Fertilization is predominantly internal, being facilitated by a spermatophore (packet of sperm) that the female picks up. Many caudates have an intricate and complex courtship ritual that is unique to their species. Eggs can be single or laid in groups/clumps and may be cared for by one or both parents. A few species, like the fire salamander (Salamandra salamandra), retain their eggs and give birth to tadpoles or even completely metamorphosed terrestrial baby salamanders. Caudate tadpoles typically possess branched, prominent external gills (these are internal or less obvious in anuran tadpoles). They undergo gradual metamorphosis into adult form in the same way as anurans.
The least numerous and least known of the amphibians, the order Gymnophonia currently contains around 200 species in 10 families. Part of the reason for this group being relatively poorly known is that most species are burrowers in leaf litter and moist soil, though some are aquatic. They can therefore be difficult animals to survey and study effectively, and detailed information about their distribution and fascinating ecology is only just becoming known. Caecilians are restricted to the tropics.
All caecilians share the same basic body pattern (Fig. 1.5): an elongated, limbless and virtually tail-less body like that of a large earthworm (for which they are sometimes mistaken). The eyes are tiny and indistinct. Their skins are smooth but appear scaly in species that have segmented rings (annuli) around their bodies. All the amphibian groups have extraordinary characteristics and caecilians are no exception. They have (uniquely) evolved a small, mobile tentacle below each eye. These retractable tentacles aid in sensing prey items and mates in the caecilians’ underground world where good eyesight would be useless. Additionally, though primitive and simplistic in appearance, they utilize different reproductive strategies. Fertilization is internal, with about half of all species producing eggs that hatch into gilled larvae, and the others giving birth to young that have developed within the female. Courtship in this group is very poorly known.
Some female caecilians, depending on the species, produce a kind of internal milk to feed their developing embryos, and some, like Boulengerula taitanus of Kenya, even grow and shed special layers of skin for their hatched larvae to eat. The larvae rasp this skin off their mother’s body with special baby teeth (see Kupfer et al., 2006). The resemblance to earthworms is therefore entirely coincidental!