Evaluating Methods for Counting Cryptic Carnivores

Abstract Numerous techniques have been proposed to estimate carnivore abundance and density, but few have been validated against populations of known size. We used a density estimate established by intensive monitoring of a population of radiotagged leopards (Panthera pardus) with a detection probability of 1.0 to evaluate efficacy of track counts and camera-trap surveys as population estimators. We calculated densities from track counts using 2 methods and compared performance of 10 methods for calculating the effectively sampled area for camera-trapping data. Compared to our reference density (7.33 ± 0.44 leopards/100 km2), camera-trapping generally produced more accurate but less precise estimates than did track counts. The most accurate result (6.97 ± 1.88 leopards/100 km2) came from camera-trap data with a sampled area buffered by a boundary strip representing the mean maximum distance moved by leopards outside the survey area (MMDMOSA) established by telemetry. However, contrary to recent suggestions, the traditional method of using half the mean maximum distance moved from photographic recaptures did not result in gross overestimates of population density (6.56 ± 1.92 leopards/100 km2) but rather displayed the next best performance after MMDMOSA. The only track-count method comparable to reference density employed a capture–recapture framework applied to data when individuals were identified from their tracks (6.45 ± 1.43 leopards/100 km2) but the underlying assumptions of this technique limit more widespread application. Our results demonstrate that if applied correctly, camera-trap surveys represent the best balance of rigor and cost-effectiveness for estimating abundance and density of cryptic carnivore species that can be identified individually.

[1]  David R. Anderson,et al.  Evaluation of Two Density Estimators of Small Mammal Population Size , 1985 .

[2]  R. B. Martin,et al.  Survey of the status of the Leopard (Panthera pardus) in sub-saharan Africa : report to the CITES secretariat, draft , 1987 .

[3]  N. Silvy,et al.  Estimating Bobcat Abundance Using Automatically Triggered Cameras , 2006 .

[4]  P. Stander.  Spoor counts as indices of large carnivore populations: the relationship between spoor frequency, sampling effort and true density , 1998 .

[5]  J. Squires,et al.  The Efficacy of Obtaining Genetic-Based Identifications from Putative Wolverine Snow Tracks , 2006 .

[6]  G. Gale,et al.  Human disturbance affects habitat use and behaviour of Asiatic leopard Panthera pardus in Kaeng Krachan National Park, Thailand , 2007, Oryx.

[7]  James D. Nichols,et al.  Analysis and Management of Animal Populations: Modeling, Estimation and Decision Making , 2002 .

[8]  M. Gusset,et al.  Estimating larger carnivore numbers from track counts and measurements , 2005 .

[9]  Darryl I. MacKenzie,et al.  The use of photographic rates to estimate densities of tigers and other cryptic mammals: a comment on misleading conclusions , 2002 .

[10]  Philip Riordan,et al.  Unsupervised recognition of individual tigers and snow leopards from their footprints , 1998 .

[11]  P. Griegsmith.  Quantitative plant ecology. , 1957 .

[12]  F. Dyke,et al.  Use of road track counts as indices of mountain lion presence , 1986 .

[13]  David R. Anderson,et al.  Statistical inference from capture data on closed animal populations , 1980 .

[14]  D. Stoner,et al.  Evaluation of Cougar Population Estimators in Utah , 2006 .

[15]  Paul Beier,et al.  Power of track surveys to detect changes in cougar populations , 1996 .

[16]  David R. Anderson,et al.  Small-mammal density estimation: A field comparison of grid-based vs. web-based density estimators , 2003 .

[17]  James D. Nichols,et al.  Science deficiency in conservation practice: the monitoring of tiger populations in India , 2003 .

[18]  K. S. Smallwood,et al.  A track count for estimating mountain lion Felis concolor californica population trend , 1995 .

[19]  M. C. Rutherford,et al.  The vegetation of South Africa, Lesotho and Swaziland. , 2006 .

[20]  A. Paviolo,et al.  Density, habitat use and activity patterns of ocelots (Leopardus pardalis) in the Atlantic Forest of Misiones, Argentina , 2006 .

[21]  S. T. Buckland,et al.  Estimating Animal Abundance , 2002 .

[22]  Andrew J. Noss,et al.  The use of camera traps for estimating jaguar Panthera onca abundance and density using capture/recapture analysis , 2004, Oryx.

[23]  Marc Kéry,et al.  ESTIMATION OF OCELOT DENSITY IN THE PANTANAL USING CAPTURE–RECAPTURE ANALYSIS OF CAMERA-TRAPPING DATA , 2003 .

[24]  P. Stander,et al.  Tracking and the interpretation of spoor: a scientifically sound method in ecology , 2009 .

[25]  R. Jackson,et al.  Estimating Snow Leopard Population Abundance Using Photography and Capture–Recapture Techniques , 2006 .

[26]  R. Slotow,et al.  Feeding habitat selection by hunting leopards Panthera pardus in a woodland savanna: prey catchability versus abundance , 2007, Animal Behaviour.

[27]  Marianne K. Soisalo,et al.  Estimating the density of a jaguar population in the Brazilian Pantanal using camera-traps and capture–recapture sampling in combination with GPS radio-telemetry , 2006 .

[28]  Kenneth H. Pollock,et al.  Large scale wildlife monitoring studies: statistical methods for design and analysis , 2002 .

[29]  C. O. Mohr,et al.  Table of equivalent populations of North American small mammals , 1947 .

[30]  Y. Jhala,et al.  Identification of individual tigers (Panthera tigris) from their pugmarks , 2005 .

[31]  P. Geissler,et al.  Density estimation in wildlife surveys , 2004 .

[32]  K. S. Smallwood,et al.  A rigorous technique for identifying individual mountain lions Felis concolor by their tracks , 1993 .

[33]  R. Kays,et al.  Using Patterns in Track-Plate Footprints to Identify Individual Fishers , 2007 .

[34]  J. Nichols,et al.  ESTIMATION OF TIGER DENSITIES IN INDIA USING PHOTOGRAPHIC CAPTURES AND RECAPTURES , 1998 .

[35]  Gary C. White,et al.  Population Estimation with Radio-Marked Animals , 2001 .

[36]  C. Nations,et al.  Monitoring Amur tiger populations: characteristics of track surveys in snow , 2002 .

[37]  P. Stephens,et al.  Estimating population density from indirect sign: track counts and the Formozov–Malyshev–Pereleshin formula , 2006 .