Data for fitting spatial capture-recapture (SCR) models to estimate spatially explicit demographics of Mojave desert tortoises on a demography plot in California, USA

These data are comprised of input files formatted for fitting spatial capture-recapture (SCR) models to estimate Mojave desert tortoise (Gopherus agassizii) density and sex by size class compositions on a previously unsampled demography plot in the Mojave Desert in California, USA. Data were collected during capture-mark-recapture surveys to identify tortoise sign on a 1-km2 plot within the South Range of U.S. Department of Navy - Naval Air Weapons Station China Lake (NAWSCL). Surveys were conducted over four days during September 2022. Data were collected as part of a study to estimate tortoise population demographics over time on NAWSCL.

Methods
Data were collected from mark-recapture Mojave desert tortoise (Gopherus agassizii) demographic plot surveys within a previously unsampled 1-kilometer x 1-kilometer area over four days in September 2022 within the south range of U.S. Department of Navy - Naval Air Weapons Station China Lake, California, USA. During surveys, all tortoise signs (e.g. live tortoises, carcasses, and scat) were recorded by surveyors walking transects. In addition, surveyors recorded their daily survey tracks using a global positioning system (GPS) units. All tortoise detection data from 25 tortoises were converted to three-dimensional spatially explicit detection histories and plotted with surveyors’ GPS tracks to discretize a continuous grid of ‘effective detectors’ encompassing all tortoise detections and tracks. Two detection data files were formatted for fitting spatial capture-recapture (SCR) models to estimate Mojave desert tortoise (Gopherus agassizii) density and sex by size class compositions of the plot site. Tortoise detection data are organized by plot identity, tortoise identity, occasion (day of detection during surveys), trap (specific grid cell where tortoise was detected), location (tortoise location recorded upon detection), sex (female, male, juvenile, or unknown), age (adult or juvenile), and sex by age (female adult, male adult, juvenile, unknown adult). Detector data are organized by trap (grid cell identity from discretized grid of effective detectors), x (UTM Easting of trap), y (UTM Northing of trap), and effort (occasion-specific surveyor search effort).