Mammalian carnivores are a difficult group of species to study, as they tend to be rare and secretive. Traditionally most studies of carnivore ecology used methodologies that required physically capturing individuals (so called ‘invasive’ techniques), with additional data deriving from either radiotelemetry or recapture events. Problematically, such approaches often resulted in studies that focused on just a few individuals or on relatively small spatial scales. Gaining a better understanding of these species and their role in the broader community was often hindered by a lack of financial resources to study more animals over a broader spatial scale. Furthermore, even when researchers have mustered these financial resources, in many parts of the world legal, social and moral norms made studies that require the physical capture of carnivores difficult, if not outright impossible, to conduct.

In an attempt to overcome these limitations, carnivore biologists have been at the forefront of efforts to develop new techniques to study these animals without having to physically capture them. These ‘non-invasive’ techniques derive from modifications to ancient methods, such as spoor identification and animal tracking, as well as adaptations of the latest molecular genetic fingerprinting technology. Because of the increased opportunities to gain novel insights on an enigmatic group of species, there has been an exponential growth in the refinement and use of non-invasive techniques. Yet with this growth has come concerns, voiced especially by those who are more attuned to the strengths and limitations of noninvasive techniques. As these methods are being increasingly used, many researchers are at fault for either using the techniques inappropriately and drawing flawed conclusions, or failing to gain the most from their datasets.

It is such concerns that are an important driver for this edited volume, which brings together carnivore researchers from the USA and Canada to discuss the nuances of non-invasive techniques from a field and data analysis perspective. Twelve chapters focus on such topics as survey design, specific non-invasive methods (such as track stations, remote cameras, hair collection, snow tracking, scat surveys and scat detecting dogs), laboratory techniques and approaches to data analysis. Discussions of the individual techniques make up the bulk of the volume and the detailed explanation of both the theoretical underpinnings as well as practical field considerations in the use of the techniques will be much appreciated by researchers who consider using these methods. However, an important drawback of this book is that the focus is limited to North American carnivores. This is unfortunate, as much of the early development and scientifically rigorous application of non-invasive techniques for carnivore population surveys and density estimates stem from work in Asia, Europe and Africa. Furthermore, it is in some of these developing countries that non-invasive techniques for monitoring carnivores are most crucially needed because of the difficulties in conducting invasive research. Although the theoretical aspect of the survey techniques may remain the same, the practical application in some of these regions may differ vastly due to differences in local field considerations.

This volume derives from a conference held in mid-2005. Given that three years have passed, and given that techniques rapidly evolve, is the work up-to-date? If the goal of a reader is to gain a basic feeling for how to conduct a non-invasive study and to better understand the problems that are intrinsic to non-invasive work, then yes, this book is a good place to start. However, if the reader is searching for the best technique, a trip to the primary literature and conversations with researchers already applying these techniques would be well advised. For example, researchers new to the field would be hard pressed to find film cameras that generated much of the insights discussed in several chapters. Furthermore, readers will still have to think long and hard about how to analyse the non-invasively generated data. Sophisticated approaches are often necessary, especially where multiple techniques are used, since different techniques result in different detection efficiencies and biases that need to be treated as covariates when modelling the response variable of interest. While the editors and authors recognize the changing nature of these techniques, and go to great effort to emphasize what the future might bring, readers must nonetheless recognize that the application of these techniques and the assessment of the non-invasively generated data are becoming increasingly sophisticated, and as such a reliance on this book alone is not a good idea. Rather, this volume should be treated by readers as a good first step to gaining an overview of the use of these non-invasive techniques.