A framework for validating noninvasive genetic spatial capture-recapture
studies for rare and elusive species
Abstract
Accurately estimating abundance is a critical component of monitoring
and recovery of rare and elusive species. Spatial capture-recapture
(SCR) models are an increasingly popular method for robust estimation of
ecological parameters. We provide a maximum likelihood analytical
framework to assess results from empirical studies to inform SCR
sampling design, using both simulated and empirical data from
non-invasive genetic sampling of seven boreal caribou populations
(Rangifer tarandus caribou) which varied in range size and estimated
population density. We use simulated population data with varying levels
of clustered distributions to quantify the impact of non-independence of
detections on density estimates, and empirical datasets to explore the
influence of varied sampling intensity on the relative bias and
precision of density estimates. Simulations revealed that clustered
distributions of detections did not significantly impact relative bias
or precision of density estimates. The empirical genotyping success rate
was 95.1%. Empirical results indicated that reduced sampling intensity
had a greater impact on density estimates in smaller ranges. The number
of captures and spatial recaptures were strongly correlated with
precision, but not relative bias. The best sampling designs did not
differ with estimated population density but differed between large and
small ranges. We provide an efficient framework implemented in R to
estimate the detection parameters required when designing SCR studies.
The framework can be used when designing a monitoring program to
minimize effort and cost while maximizing effectiveness, which is
critical for informing wildlife management and conservation.