Phenotypical characterization of African savannah and forest elephants, with special emphasis on hybrids: the case of Kibale National Park, Uganda


J ULIE BONNALD,RAPHAËL CORNETTE,MAËLLIE P IC H A RD EDWA R D ASALU and S ABRINA KRIEF


Abstract The IUCN now recognizes the savannah Lox- odonta africana and forest Loxodonta cyclotis elephants to be separate species. Despite ecological, behavioural and morphological differences, and different habitat ranges, genetic studies confirm that the two species and hybrids coexist in forest–savannah ecotones. However, the hybrid phenotypes have not yet been described. In this survey we examined whether the phenotypes of the two species and of hybrids can be distinguished. In the first step, we used a machine learning algorithm (K-nearest neighbours) to compare 296 reference images of African elephants from five forest areas and six savannah areas where hybrids have not been recorded, confirming that six morphological criteria can be used to distinguish the species with more than 90% confidence. In the second step, we analysed 1,408 videos of elephants from 14 camera traps in Sebitoli, in Kibale National Park, Uganda, part of the main hybrid- ization area. We used a multiple correspondence analysis and a species assignment key, highlighting the presence of three categories of phenotypes. Compared to the savannah and forest phenotypes (36.8 and 12.1%, respectively), the intermediate phenotypes, which could include hybrids, were more frequent (51.1%). Further studies combining morphology and genetics of the same individuals will be ne- cessary to refine this species assignment key to characterize phenotypes confidently. This non-invasive, fast and inex- pensive phenotypical-based method could be a valuable tool for conservation programmes.


Keywords African elephant, camera traps, hybridization area, Kibale National Park, morphological criteria, pheno- type, Sebitoli, Uganda


Supplementary material for this article is available at doi.org/10.1017/S0030605321001605


Introduction


cause of poaching for ivory or habitat reduction and frag- mentation (Maisels et al., 2013; Gobush et al., 2021a,b). Today, c. 415,000 African elephants remain in 37 countries (Thouless et al., 2016). After a long-standing debate, African elephants are now considered by IUCN to be two distinct species (Hart et al., 2021): the savannah elephant Loxodonta africana, categorized as Endangered on the IUCN Red List (Gobush et al., 2021a) and the forest elephant Loxodonta cyclotis, categorized as Critically Endangered (Gobush et al., 2021b). The two species are known to have their own behavioural


S JULIE BONNALD* (Corresponding author, orcid.org/0000-0003-1407-5241,


julie.bonnald@mnhn.fr) and SABRINA KRIEF*( orcid.org/0000-0003-3814- 7641) UMR7206 Eco-Anthropologie, Muséum National d’Histoire Naturelle, CNRS, Paris VII, 17 place du Trocadéro, Paris, France


RAPHAËL CORNETTE ( orcid.org/0000-0003-4182-4201) Institut de Systématique, Évolution, Biodiversité, Muséum National d’Histoire Naturelle, CNRS, Sorbonne Université, EPHE, Université des Antilles, Paris, France


MAËLLIE PICHARD Sebitoli Chimpanzee Project, Fort Portal, Uganda EDWARD ASALU Uganda Wildlife Authority, Kampala, Uganda *Also at: Sebitoli Chimpanzee Project, Fort Portal, Uganda


Received 18 March 2021. Revision requested 5 July 2021. Accepted 29 October 2021. First published online 13 June 2022.


and ecological features (Roth & Douglas-Hamilton, 1991; Grubb et al., 2000; Turkalo & Fay, 2001). Some anatomical and morphological characteristics such as body size, ear shape, tusk orientation and depth of the temporal fossae are sufficiently different to distinguish the two species (Fallon, 1944; Morrison-Scott, 1947; Pfeffer, 1989;Shoshani, 1993;Grubb et al., 2000;Debruyne, 2003;Fowler&Mikota, 2006). However, most morphological studies comparing the two species have focused on bones/skulls and not on living individuals (van der Merwe et al., 1995; Grubb et al., 2000; Debruyne, 2003). Nevertheless, differences depending on age and sex as well as regional morphological variations ob- served in the savannah elephant, particularly in the shape and size of their ears and tusks, could limit the use of these morphological characteristics in practice (Hanks, 1972; Pfeffer, 1989). Despite their habitat differences, the geographical distri-


butions of the two species overlap, and both occur in the for- est–savannah ecotones of Central and West Africa (Pfeffer, 1989; Groves & Grubb, 2000), although there have been few morphological observations of intermediate elephants reported in these areas (Pfeffer, 1989; Groves & Grubb, 2000; Debruyne, 2003). To date, genetic studies have pro- vided evidence of hybrids in five locations: Garamba National Park in the north-eastern Democratic Republic of the Congo (DRC) (Roca et al., 2001, 2005; Comstock


This is an Open Access article, distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike licence (https://creativecommons.org/licenses/by-nc-sa/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the same Creative Commons licence is included and the original work is properly cited. The written permission of Cambridge University Press must be obtained for commercial re-use. Oryx, 2023, 57(2), 188–195 © The Author(s), 2022. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605321001605


evere population declines amongst African elephants Loxodonta sp. are occurring throughout their range be-


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