Advances in Noninvasive Sampling through a Better Understanding of Target-Species Ecology


Noninvasive Survey Methods for Carnivores . Long, R. A., P.MacKay, W. J.Zielinski, and J. C.Ray , editors . 2008 . Island Press , Washington , D.C. 385 pp. $45.00 (paperback) . ISBN 978-1-59726-120-3 .

The release of Noninvasive Survey Methods for Carnivores coincided with the February 2008 discovery of a wolverine (Gulo gulo) in Tahoe National Forest, near Truckee, California. Without current advances in noninvasive survey methodology, as Noninvasive Survey Methods examines, it is likely that the detection of the wolverine would not have occurred. Wolverines had not been confirmed in the state since the 1920s (Grinnell et al. 1937) and were presumed extirpated. Since this recent discovery, a concerted effort has been made to search for more wolverines in the area with a variety of noninvasive survey methods, such as detection dogs, hair snares, and camera stations—all methods examined in detail within this comprehensive volume. As noninvasive survey methods become more refined, cost-efficient, and easier to deploy, monitoring rare and elusive species on the landscape level can only get more interesting and exciting. Noninvasive Survey Methods summarizes several decades of research by dedicated investigators who saw the need to survey for carnivores noninvasively and provides information on hundreds of scientific papers that fine tune and improve on many noninvasive survey methods.

What does noninvasive methods mean and why are they important? The editors define noninvasive as “not requiring target animals to be directly observed or handled by the surveyor” (p. 1). Animals may be observed on camera, their tracks can be imprinted, or samples of their hair can be obtained—there are numerous noninvasive methods, all of which are described in detail. Although invasive methods (live trapping and radiotelemetry) can provide high-resolution data with just a few individuals, noninvasive survey methods can be deployed over large areas and are capable of monitoring entire populations. Although not mentioned in the book, noninvasive methods do not necessarily require the “take” permits from federal and state agencies that live trapping does, which allows researchers to avoid a lengthy permitting process and to complete surveys quickly during the appropriate season.

Why carnivores? Carnivores are “frequently evaluated as potential focal species for regional conservation efforts and ecosystem management” (p. 227). Carnivores with large landscape needs, such as the grizzly bear (Ursus arctos), are often considered umbrella species because it is thought that the area of habitat required to support viable and sustainable populations of these species will protect habitat for other species with smaller area requirements, thus advancing the agenda of wildlife conservation (Carroll et al. 2001). Noninvasive Survey Methods provides researchers with the tools to ensure that future research involving carnivore conservation remains feasible and possible with the use of noninvasive survey methods.

Noninvasive Survey Methods for Carnivores is divided into 12 chapters, covering noninvasive survey methods, statistical analyses, genetic analysis methods, and survey design. The chapters are arranged chronologically according to the appearance of the particular method in the field: natural sign (tracks and scats), track stations, remote cameras, hair-snag devices and collection, and scat-detection dogs. At the end of most chapters, the editors include interesting case studies of practical applications of the methods discussed in the chapter. Other chapters include useful glossaries to expand on method-specific terms that may have otherwise been unclear to the reader; appendices of complex data sets; examples of field-data forms; and tables, graphs, and figures to enhance clarity and readability.

The editors emphasize that the book is a comprehensive guidebook—guiding researchers along practical routes to accomplish their research goals. Much of the volume focuses on four important research objectives: assessing occurrence and distribution, assessing relative abundance, estimating abundance, and monitoring. As always, the most suitable study design depends on the survey objectives, ecology and population status of the target carnivore, where the survey will take place, and logistical constraints.

Designing a study is as much an art as a science. Theoretical and simulation results provide useful guidance about the expected outcome of a study given certain assumptions, analytic techniques and designs. But these results must be tempered with common sense, expert knowledge of the system under study, and occasionally, lateral thinking. (MacKenzie & Royle 2005:40)

The beauty of this book is that the editors and authors have done a lot of legwork for researchers interested in using noninvasive survey methods. They have evaluated each method, provided the pros and cons of each method and its effectiveness in detecting target species, and recommended which method should be used for certain research objectives. The authors remind us that the lack of clear objectives will often lead to endless debate about design issues as there has been no specification for how the collected data will be used in relation to science and/or management; hence, judgments about the ‘right’ data to be collected cannot be made (pp. 39–40; MacKenzie & Royle 2005:1107).

Noninvasive Survey Methods for Carnivores encourages creativity and the use of one noninvasive survey method either in conjunction with or prior to another method for better survey results, provided the methods do not interfere with one another. Running detection dogs through a study site to determine the species baseline inventory before setting up camera or track stations is a good idea because these stations typically use scent lure that “unnaturally” attract target species from outside of the study site. Some noninvasive methods can also be used to record the effectiveness of another noninvasive method, such as using a remote still or video camera to record carnivore behaviors around hair snags.

Although this book offers much information on various noninvasive survey methods, there are still research gaps that need to be filled. The use of digital remote cameras is fairly new and the advantages and effectiveness over older technology (film cameras) appear to be obvious; however, more side-by-side comparisons are required, including comparing one digital camera design over another (Clark & Orland 2008). Other research to scientifically test different scent and long-distance calling lures that are on the market is needed. For example, a wide variety of carnivores are attracted to skunk-based scent lures, but ironically, little effort has gone into evaluating methods to detect skunks themselves (pp. 281 and 317).

As with any book written by several authors, unique writing styles are evident. For example, chapter 4 is a rather difficult chapter to read, even though the subject matter is straightforward and should been easy to understand. I had to reread several sections in order to identify the main point. In contrast, chapter 5 was a pleasure to read; it is very well written and has excellent flow. This book is a very useful guide in the field of noninvasive survey methods, and any researcher interested in using one or more of the methods discussed should take advantage of this book. A book summarizing noninvasive survey methods was overdue, and the editors and authors have outdone themselves in advancing the field. I hope, as a researcher, this book will become an important cornerstone in carnivore conservation biology.