Optimizing the automated recognition of individual animals to support population monitoring.

Published version
Repository DOI

Type
Article
Change log
Authors
Horswill, Catharine  ORCID logo  https://orcid.org/0000-0002-1795-0753
Rabaiotti, Daniella  ORCID logo  https://orcid.org/0000-0003-4123-2492
Ewers, Robert M 
Abstract

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, noninvasive 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 catalogs 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 intraspecific variation in the performance of software packages, we compare identification accuracy between two populations (in Kenya and Zimbabwe) that have markedly different coat coloration patterns. The process of selecting suitable images was automated using convolutional neural networks 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 preprocessing 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.

Description

Funder: Research England

Keywords
Hotspotter, I3S‐Pattern, Lycaon pictus, WildID, automated individual recognition, photographic identification
Journal Title
Ecol Evol
Conference Name
Journal ISSN
2045-7758
2045-7758
Volume Title
13
Publisher
Wiley
Sponsorship
Natural Environment Research Council (NE/T001348/1)