Quantifying and correcting for scat removal in noninvasive carnivore scat surveys

Abstract

Scat surveys are commonly used to monitor wildlife populations. For carnivores, surveys are typically conducted along roads and trails. Scats available for detection may not relect scats deposited and variation in disappearance may bias results. Previous research has investigated natural decay and deterioration, but scats deposited along roads or trails are likely inluenced to a greater degree by anthropogenic disturbance in some systems. We used experimental plots to evaluate variation in scat removal for two model carnivores, coyote Canis latrans and kit fox Vulpes macrotis, along roads in the Great Basin Desert, USA. Using parametric survival regression, we predicted scat survival and developed persistence-rate correction factors, which were applied to results from relative abundance scat surveys conducted along 15 transects. Kit fox scats disappeared more rapidly than coyote scats, with 3.3% and 10.6%, respectively, persisting through 42 days. At 14 days, 90.8-41.7% of scats had been removed across road types. Survival models indicated species, road type, scat position and daily traic were important predictors of scat persistence. Applying persistence-rate correction factors to scat survey results altered the inferred relative abundances. Across seasons, mean corrected:uncorrected relative abundance ratios ranged from 1.0-91.2 for coyotes and 1.3-139.3 for kit foxes, with higher mean ratios being inluenced by high corrected relative abundances on roads with high traic volumes. Understanding scat removal rates and patterns can improve inferences from surveys. Persistence-rate correction factors can be used to reduce bias in indices of abundance, but caution should be used when removal rates are high. Knowledge of spatial variation in persistence can elucidate concerns of false-positives and false-negatives in occupancy and capture-recapture studies. Considering the disparity in scat removal between species and among road types and positions, we recommend practitioners quantify and consider variation in removal when interpreting scat survey results.

The roles of habitat and intraguild predation by coyotes on the spatial dynamics of kit foxes

“…Road characteristics can influence scat persistence (Lonsinger et al. ) and detection (Kluever et al. ).…”

“…We characterized the road type of each transect as (1) unmaintained two‐track road, or maintained (2) single‐lane or (3) two‐lane gravel road (sensu Lonsinger et al. ). Scat detection may also be influenced by the presence of snow, survey date, and/or survey time (Harris et al.…”

Integrating multiple genetic detection methods to estimate population density of social and territorial carnivores

“…Thus, we sampled during the winter coyote breeding season when the probability of detection should have been highest (Long et al 2008). Because the majority of transects were located in areas that were closed to vehicular access by the public, we did not apply correction factors that may be needed for scat transect sampling that occurs in areas subjected to high scat removal rates (Lonsinger et al 2016).…”

Estimating densities for sympatric kit foxes (Vulpes macrotis) and coyotes (Canis latrans) using noninvasive genetic sampling

“…Efforts to monitor kit foxes and coyotes in the Great Basin Desert have included predator control indices, scat deposition surveys, live capture, den monitoring, and radiotelemetry (Arjo et al 2007;Kozlowski et al 2012;Kluever et al 2013;Dempsey et al 2014Dempsey et al , 2015. Scat deposition surveys provide indices of relative abundance (Gese 2001) but may suffer from misidentification of sign (Lonsinger et al 2015b) and often fail to account for spatiotemporal variation in scat detection (Kluever et al 2015;Lonsinger et al 2016). Live captures and radiotelemetry are expensive and time-consuming (Gese 2001), limiting the spatial and temporal extent of monitoring, and den monitoring often requires telemetered animals to locate dens (e.g., Arjo et al 2003).…”