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PDF: Gompper et al 2006 carnivore survey techniques

 Gompper, M.E., R.W. Kays, J.C. Ray, S.D. LaPoint, D.A. Bogan, and J.A. Cryan  2006. A comparison of non-invasive techniques to survey carnivore communities in Northeastern North America. Wildlife Society Bulletin, 34, 1142-1151.

Carnivores are notoriously difficult to survey due in large part to their relative rarity across the landscape and wariness towards humans. Several non-invasive methods may aid in overcoming these difficulties, but there has been little discussion of the relative merits and biases of these techniques. We assess the value of five non-invasive techniques based on results from two multi-year studies of carnivores (including members of the Carnivora and Didelphidae) in Northeastern North American forests. Two metrics were particularly valuable in assessing the species-specific value of any particular survey technique: latency to initial detection (LTD) and probability of detection (POD). We found differences in the value of techniques in detecting different species. For mid-sized species (raccoon [Procyon lotor], fisher [Martes pennanti], opossum [Didelphis virginiana], and domestic cat [Felis catus]), camera traps and track-plates were approximately equivalent in detection efficiency, but the potential for wariness towards the survey apparatus resulted in higher LTD for track-plates than for cameras. On the other hand, track-plates detected small carnivores (marten [Martes americana], and weasels [Mustela spp.]) more often than cameras, and had higher PODs for small and mid-sized species than did cameras. Cameras were efficient mechanisms for surveying bears (Ursus americanus; low LTD, high POD) but functioned poorly for discerning the presence of coyotes (Canis latrans; high LTD, low POD). Scat surveys and snow tracking were the best methods for coyotes, which avoided camera traps and artificial tracking surfaces. Analyses of fecal DNA revealed that trail-based fecal surveys were inefficient at detecting species other than coyotes, with the possible exception of foxes. Genetic analyses of feces and snow tracking revealed the presence of foxes at sites where other techniques failed to discern these species, suggesting that cameras and track-plates are inefficient for surveying small canids in this region. The LTD of coyotes by camera traps was not correlated with their abundance as indexed by scat counts, but for other species this metric may offer an opportunity to assess relative abundance across sites. Snow-tracking surveys were particularly robust (high POD) for detecting species active in winter, and may be more effective than both cameras and track-plates where conditions are suitable. We recommend that survey efforts targeting multiple members of the carnivore community use multiple independent techniques and incorporate mechanisms to truth their relative value.