DOI: 10.5061/dryad.js76054
title: Data from: The challenges of recognising individuals with few distinguishing features: identifying red foxes Vulpes vulpes from camera-trap photos

description: Over the last two decades, camera traps have revolutionised the ability of
 biologists to undertake faunal surveys and estimate population densities,
 although identifying individuals of species with subtle markings remains
 challenging. We conducted a two-year camera-trapping study as part of a
 long-term study of urban foxes: our objectives were to determine whether
 red foxes could be identified individually from camera-trap photos, and
 highlight camera-trapping protocols and techniques to facilitate photo
 identification of species with few or subtle natural markings. We
 collected circa 800,000 camera-trap photos over 4945 camera days in
 suburban gardens in the city of Bristol, UK: 152,134 (19 %) included
 foxes, of which 13,888 (9 %) contained more than one fox. These provided
 174,063 timestamped capture records of individual foxes; 170,923 were of
 foxes ≥ 3 months old. Younger foxes were excluded because they have few
 distinguishing features. We identified the individual (192 different
 foxes: 110 males, 49 females, 33 of unknown sex) in 168,417 (99 %) of
 these capture records; the remainder could not be identified due to poor
 image quality or because key identifying feature(s) were not visible. We
 show that carefully designed survey techniques facilitate individual
 identification of subtly-marked species. Accuracy is enhanced by
 camera-trapping techniques that yield large numbers of high resolution,
 colour images from multiple angles taken under varying environmental
 conditions. While identifying foxes manually was labour-intensive,
 currently available automated identification systems are unlikely to
 achieve the same levels of accuracy, especially since different features
 were used to identify each fox, the features were often inconspicuous, and
 their appearance varied with environmental conditions. We discuss how
 studies based on low numbers of photos, or which fail to identify the
 individual in a significant proportion of photos, risk losing important
 biological information, and may come to erroneous conclusions.
description: image_list_field_descriptionsExplanation of field names in image_list.csvimage_listTable of all fox images and their associated fox IDs, for one patch surveyed in summer 2013, autumn 2013, winter 2013-14 and spring 2014. Field descriptions are in image_list_field_descriptions.csv.survey_1_summer_2013 image filesCamera trap photos of foxes taken in one garden ('patch') during a 40-day camera trap survey in summer 2013. Photos were taken using a Scoutguard SG565F-8M motion-sensing camera trap.survey_1_summer_2013.tar.gzsurvey_5_autumn_2013 image filesCamera trap photos of foxes taken in one garden ('patch') during a 40-day camera trap survey in autumn 2013. Photos were taken using a Scoutguard SG565F-8M motion-sensing camera trap.survey_5_autumn_2013.tar.gzsurvey_10_winter_2013 image filesCamera trap photos of foxes taken in one garden ('patch') during a 40-day camera trap survey in winter 2013-14. Photos were taken using a Scoutguard SG565F-8M motion-sensing camera trap.survey_10_winter_2013.tar.gzsurvey_17_spring_2014 image filesCamera trap photos of foxes taken in one garden ('patch') during a 40-day camera trap survey in spring 2014. Photos were taken using a Scoutguard SG565F-8M motion-sensing camera trap.survey_17_spring_2014.tar.gzREADME for all image files