DOI: 10.5061/dryad.r2280gb8k
title: Data from: Density-dependent space use affects interpretation of camera trap detection rates

description: Camera-traps (CTs) are an increasingly popular tool for wildlife survey
 and monitoring. Estimating relative abundance in unmarked species is often
 done using detection rate as an index of relative abundance, which assumes
 a positive linear relationship with true abundance. This assumption may be
 violated if movement behavior varies with density, but the degree to which
 movement is density-dependent across taxa is unclear. The potential
 confounding of population-level relative abundance indices by movement
 depends on how regularly, and by what magnitude, movement rate and
 home-range size vary with density. We conducted a systematic review and
 meta-analysis to quantify relationships between movement rate, home range
 size, and density, across terrestrial mammalian taxa. We then simulated
 animal movements and CT sampling to test the effect of contrasting
 movement scenarios on CT detection rates. Overall, movement rate and home
 range size were negatively correlated with density and positively
 correlated with one another. The strength of the relationships varied
 significantly between taxa and populations.  In simulations,
 detection rates were related to true abundance but underestimated change,
 particularly for slower moving species with small home ranges. In
 situations where animal space use changes markedly with density, we
 estimate that up to thirty percent of a true change in abundance may be
 missed due to the confounding effect of movement, making trend estimation
 more difficult. The common assumption that movement remains constant
 across densities is therefore violated across a wide range of mammal
 species. When studying unmarked species using CT detection rates,
 researchers and managers should consider that such indices of relative
 abundance reflect both density and movement. Practitioners interpreting
 changes in detection rates should be aware that observed differences may
 be biased low relative to true changes in abundance, and that further
 information on animal movement may be required to make robust inferences
 on population trends.
description: Data files are contained in the zipped folder
 <strong>BroadleyEtAl_EcolEvol_Data.zip</strong>
 <strong>MetaPercent_HRMovt.csv, MetaPercent_DensMovt.csv,
 and MetaPercent_DensHR.csv, </strong>contain data used to graph
 changes in density, movement rate, and home range size. Indicated are the
 author, species, each parameter as a percentage of that of the reference
 population (where the reference is the population with the lowest value
 for the parameter displayed on the x-axis), and the x-axis parameter as a
 fold change. <strong>MetaForest_HRMovt.csv,
 MetaForest_DensMovt.csv, and MetaForest_DensHR.csv, </strong>contain
 data used to conduct the meta analysis (i.e., data for each study that
 provided sufficient statistical information for the given parameters).
  Indicated are the author and species of the study, percent change in the
 given parameters for the two populations considered, N, test statistic
 type and value, and the standardized effect size (as a correlation
 coefficient). <strong>SimulatedHitrateData.csv
 </strong>contains outputs from the movement simulations as described
 in the paper. The title of each column indicates the number of
 individuals, the scenario speed, the scenario home range size, and whether
 the data below represents the sum encounters with cameras, or the hitrate
 (detections/d). Each row represents an additional instance of the
 simulation.