Data from: The challenges of recognising individuals with few distinguishing features: identifying red foxes Vulpes vulpes from camera-trap photos

  • Jo Dorning (Contributor)

Dataset

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.,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,
Date made available14 May 2019
PublisherDryad

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