This book is perhaps the most important reference available for those interested in measuring and monitoring biological diversity in amphibians. It was produced in response to the great need of the establishment of standardized methods and protocols for sampling natural amphibian populations. It covers a vast array of topics including overview chapters on the natural history of amphibians, on the essentials of standardization and quantification of study questions, randomization and bias, replication issues, and assumptions, on research design and planning. It also includes chapters on standard monitoring and inventory techniques, marking and tracking techniques, population estimation techniques, instructions for preparation of amphibians as scientific specimens, tissue collecting protocols for biochemical analysis, and instructions and recommendations for the analysis of biodiversity data.
Audience: Conservation organizations, environmental consultants, government agencies, wildlife managers, reserve managers, students and scientists.
In the following section I provide a brief summary of the material covered in most of the chapters. I have included the names of all the chapters.
Amphibian Diversity and Natural History: An Overview
Essentials of Standardization and Quantification
This short chapter seeks to define the terms that are widely used throughout the book. Included are clear descriptions of scale and issues of randomization and bias, of the importance of replication in any study and the assumptions that underlie a specific study program. This chapter is short and serves to give the reader a foundation for these important terms and principles.
Research Design for Quantitative Amphibian Studies
The chapter deals with the theory of research design and provides a conceptual basis for the reader. The author attempts to unfold potential problems and strengths of using a hypothesis driven approach to the amphibian researcher. She covers topics such as how to choose a testable research question, how to focus the question, how to define terms that are necessarily used in amphibian biodiversity and monitoring studies (difficult terms such as "abundant"). She gives prudent advice concerning data accuracy issues when field observations are taken. She covers measurement scales, randomness, representativeness of samples, sampling methods, sample size, sample independence, all with regards to statistical analysis.
For the non-scientist she explains the idea of a null hypothesis and the 0.05 convention of statistically "significant" results (also know as 95% confidence intervals). She discusses the interplay between statistical power, effect size and sample size and ends with a good discussion of statistical versus substantive significance.
Keys to a Successful Project: Associated Data and Planning
This chapter makes recommendations for the type of additional or ancillary data one should collect along with any monitoring project. Special attention is given to weather data collection and suggestions are given for the type of instruments needed to gather these data. Temperature, precipitation, relative humidity, barometric pressure, wind speed and direction, breeding site water level, and pH are all covered. The authors describe data collection methods ranging from cheap hand-held devices to expensive automated systems. Guidelines are provided for describing habitats, localities, and sampling sites. The authors include a checklist for microhabitat characterization environmental data on should collect, as well as specimen. For example, if one is interested in pond breeding amphibians, they suggest that data be collected on pond depth (minimum, maximum and average), percentage of water surface area covered by emergent vegetation, substrate size, relative duration of pond, shoreline characterization, etc. They also provide sample datasheets sample frog call recording diagrams and a section on scientific collecting permits. Instructions are included for voucher specimen ancillary data as well as recommendations for collection sample sizes and the type of data that should be associated with each specimen.
Standard Techniques for Inventory and Monitoring
This chapter of the book outlines ten different techniques commonly used for inventory and monitoring. I will briefly discuss each technique.
1. Complete Species Inventories--The author attempts to easily explain the best ways to compile species lists or inventories for selected areas. Museum collections may be searched for existing specimens, or specimens may be collected. He discusses three different approaches concentrating mainly on what he calls "Systematic Sampling Surveys." The author stresses the importance of using an approach that is quantitative and suggests time-constrained searches (yielding a number of species collected per person hour).
2. Visual Encounter Surveys--This may be the most commonly used amphibian survey and census technique. This can be used to determine the species richness of an area, to compile a list and to estimate relative abundances of species in the area. As the name implies, this is a visual technique and is only appropriate for those amphibians that can be seen while walking through a habitat. For example this would not be an appropriate technique for some salamanders and caecilians that are fossorial in nature. In addition, this technique is sensitive to differences in habitat types. Most of the discussion is centered on open understory rainforests in Central America, but this can probably be adapted easily to other environments. Assumptions underlying this method are discusses as are different types of designs (randomized-walk, quadtrat, and transect). Randomized-walk involves walking a randomly chosen distance at a randomly chosen compass direction repeatedly. Quadrats are square sampling areas (or varying size) placed at randomly selected sites within a study area; the quadrats are exhaustively checked for amphibians, and then these numbers are used to estimate total numbers within the entire study area. Transects are straight lines that can be set up permanently, data is then collected by walking down the line and counting all amphibians seen on either side of the line.
3. Audio Strip Transects--This technique uses the voices of calling frogs to estimate relative abundances of calling males, relative abundances of all adults, species composition, breeding habitat or microhabitat use, and time of breeding for different species. Personnel must learn the advertisement calls of the appropriate species. This method is good for species that are hard to see, either because they blend in with their habitat, or because their habitat may be inaccessible (high in the trees or in thick vegetation). The details, including the assumptions and interpretations are described.
4. Quadrat Sampling-- Quadrats are square sampling areas (or varying size) placed at randomly selected sites within a study area; the quadrats are exhaustively checked for amphibians, and then these numbers are used to estimate total numbers within the entire study area. This section gives detailed directions for use.
5. Transect Sampling-- Transects are straight lines that can be set up permanently, or temporarily; data is then collected by walking down the line and counting all amphibians seen on either side of the line. Randomized transect design allows researchers to effective track species numbers, relative abundance and densities across habitat gradients.
6. Patch Sampling--This method can be used to determine the number, relative abundances, and densities of species present in discrete subunits of an area of interest. Since amphibian density and species composition can change dramatically from one type of habitat to another, this method can be a valuable tool.
7. Straight-Line Drift Fences and Pitfall Traps--These methods are used to live-trap amphibians. Animals are caught, marked and released. Upon recapture, animals with marks are recorded, and the proportion recaptured can be used to calculate population size (see Chapter 8). This section contains valuable images for drift fence placement patterns, and pitfall trap design.
8. Surveys at Breeding Sites--Since many amphibians are most visible at the breeding ponds, methods have been developed to monitor populations and look for species at those sites. This section discusses how to conduct a survey specifically at breeding sites (includes pond and stream habitats).
9. Drift Fences Encircling Breeding Sites--This section focuses on the construction and use of drift fences that encircle breeding sites (ponds in this case).
10. Quantitative Sampling of Amphibian Larvae--Larvae, especially from frogs, can number in the thousands. This section describes methods that can be employed to estimate the total number of larvae in a given area (without having to count all of them one by one!). Figures are included for construction of a "box sampler."
Supplemental Approaches to Studying Amphibian Biodiversity
This chapter describes several methods that may not be conventionally used, but could prove to be useful depending on where one chooses to study amphibian biodiversity. Item covered include, 1) the use of artificial habitats (pools and cover) to monitor amphibians, 2) using fixed automatic acoustic devices to monitor populations, 3)different tracking techniques to follow animals (radios, threat, radioactive tags), 4) night driving on roads to quantify number of moving animals, 5) using GIS (geographic information systems) as a tool to integrate amphibian information with spatial or geographic information, 6) and using group activities and field trips to gather information.
Estimating Population Size
There are many different ways to estimate population sizes. In many cases it can be a difficult task to match the correct calculation technique with the type of data gathering technique that has been used. This chapter is a very good resource because it brings together many of the techniques available to estimate population size. It also states the assumptions for each of the techniques. Again, this is a valuable resource, one that anyone interested in monitoring populations through time should read.
Analysis of Amphibian Biodiversity Data
This chapter discusses the problems of interpretation of amphibian monitoring data. Statistical procedures that are appropriate for amphibian monitoring and sampling are discussed and limitations and important statistical assumptions are explained. Examples include calculating species richness using presence absence data, 2) species abundance using individual counts and proportions, 3) species diversity, and several others. One of the most valuable sections of this chapter contains a large table that compares the different formulas to each other (with references to the original articles).
Conclusions and Recommendations
This short chapter covers the importance of inventory data and the comparability of data across time and geography.
Handling Live Amphibians
Gives recommendations on how to handle live amphibians in the most humane manner.
Techniques for marking Amphibians
This sections quickly covers different methods for marking amphibians including, pattern mapping (uses existing color patterns), different types of tags, polymers and pigment marking, transponders, toe clipping (with helpful figures), and several other methods.
Recording Frog Calls
Gives a list of necessary equipment and some helpful tips on how to get started in frog call recording.
Preparing Amphibians as Scientific Specimens
Collecting Tissue for Biochemical Analysis