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Optimising the automated recognition of individual animals to support population monitoring
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  • Tijmen de Lorm,
  • Catharine Horswill,
  • Daniella Rabaiotti,
  • Robert Ewers,
  • Rosemary Groom,
  • Jessica Watermeyer,
  • Rosie Woodroffe
Tijmen de Lorm
Imperial College London - Silwood Park Campus

Corresponding Author:[email protected]

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Catharine Horswill
Zoological Society of London Institute of Zoology
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Daniella Rabaiotti
Zoological Society of London Institute of Zoology
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Robert Ewers
Imperial College London - Silwood Park Campus
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Rosemary Groom
Zoological Society of London Institute of Zoology
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Jessica Watermeyer
African Wildlife Conservation Fund
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Rosie Woodroffe
Zoological Society of London Institute of Zoology
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Reliable estimates of population size and demographic rates are central to assessing the status of threatened species. However, obtaining individual-based demographic rates requires long-term data, which is often costly and difficult to collect. Photographic data offer an inexpensive, non-invasive method for individual-based monitoring of species with unique markings, and could therefore increase available demographic data for many species. However, selecting suitable images and identifying individuals from photographic catalogues is prohibitively time-consuming. Automated identification software can significantly speed up this process. Nevertheless, automated methods for selecting suitable images are lacking, as are studies comparing the performance of the most prominent identification software packages. In this study, we develop a framework that automatically selects images suitable for individual identification, and compare the performance of three commonly used identification software packages; Hotspotter, I3S-Pattern, and WildID. As a case study, we consider the African wild dog Lycaon pictus, a species whose conservation is limited by a lack of cost-effective large-scale monitoring. To evaluate intra-specific variation in the performance of software packages, we compare identification accuracy between two populations (in Kenya and Zimbabwe) that have markedly different coat colouration patterns. The process of selecting suitable images was automated using Convolutional Neural Nets that crop individuals from images, filter out unsuitable images, separate left and right flanks, and remove image backgrounds. Hotspotter had the highest image-matching accuracy for both populations. However, the accuracy was significantly lower for the Kenyan population (62%), compared to the Zimbabwean population (88%). Our automated image pre-processing has immediate application for expanding monitoring based on image-matching. However, the difference in accuracy between populations highlights that population-specific detection rates are likely and may influence certainty in derived statistics. For species such as the African wild dog, where monitoring is both challenging and expensive, automated individual recognition could greatly expand and expedite conservation efforts.
09 Mar 2023Submitted to Ecology and Evolution
10 Mar 2023Submission Checks Completed
10 Mar 2023Assigned to Editor
10 Mar 2023Reviewer(s) Assigned
17 May 2023Review(s) Completed, Editorial Evaluation Pending
19 May 2023Editorial Decision: Revise Minor
18 Jun 20231st Revision Received
19 Jun 2023Submission Checks Completed
19 Jun 2023Assigned to Editor
19 Jun 2023Review(s) Completed, Editorial Evaluation Pending
21 Jun 2023Editorial Decision: Accept