Social structure and demography of a remnant Asian elephant Elephas maximus population and the implications for survival


LAUREN J. HAL E,KUN S HI,TANIA C. GILBERT KEL VIN S.-H. P EH and P HI LI P RIORDAN


Abstract The Asian elephant Elephas maximus is at risk of extinction as a result of anthropogenic pressures, and remaining populations are often small and fragmented remnants, occupying a fraction of the species’ former range. Once widely distributed across China, only a max- imum of 245 elephants are estimated to survive across seven small populations. We assessed the Asian elephant population in Nangunhe National Nature Reserve in Lin- cang Prefecture, China, using camera traps during May– July 2017, to estimate the population size and structure of this genetically important population. Although detec- tion probability was low (0.31), we estimated a total popu- lation size of c. 20 individuals, and an effective density of 0.39 elephants per km2. Social structure indicated a strong sex ratio bias towards females, with only one adult male detected within the population.Most of the elephants asso- ciated as one herd but three adult females remained separ- ate from the herd throughout the trapping period. These results highlight the fragility of remnant elephant popula- tions such as Nangunhe and we suggest options such as a managed metapopulation approach for their continued survival in China and more widely.


Keywords camera trapping, demographic survival, Elephas maximus, habitat fragmentation, People’s Republic of China, population thresholds, protected areas, Yunnan Province


Supplementary material for this article is available at doi.org/10.1017/S0030605319000504


Introduction


africana, African forest elephant Loxodonta cyclotis and Asian elephant Elephas maximus, are at risk of extinction as a result of habitat loss and fragmentation. These threats are further compounded by illegal poaching for ivory, meat and skin (Blanc, 2008; Choudhury et al., 2008). Once widespread across Asia, the Asian elephant is now the most threatened of the extant species, categorized as Endangered on the IUCN Red List (Choudhury et al., 2008). There are an estimated 41,000–52,000 animals in the wild, occurring in restricted populations in remain- ing range countries (Choudhury et al., 2008). Given the increased extinction risk posed by population restriction and fragmentation (Lacy, 2000; Frankham, 2005), especially for larger-bodied species (Hilbers et al., 2017), it is important to understand the demography of the remaining small popu- lations so that effective management can be enacted. Once widely distributed over southern China, only


G


LAUREN J. HALE* and TANIA C. GILBERT* School of Biological Sciences, University of Southampton, Southampton, UK


KUN SHI† Wildlife Institute, School of Nature Conservation, Beijing Forestry University, Beijing, China


KELVIN S.-H. PEH‡ School of Biological Sciences, University of Southampton, Southampton, UK


PHILIP RIORDAN§ (Corresponding author, orcid.org/0000-0001-6285-8596)


Marwell Wildlife, Thompson’s Lane, Colden Common, Winchester, SO21 1JH, UK. E-mail philipr@marwell.org.uk


*Also at: Marwell Wildlife, Winchester, UK †Also at: Wildlife Without Borders, Chelmsford, UK ‡Also at: Conservation Science Group, Department of Zoology, University of Cambridge, Cambridge, UK §Also at: School of Biological Sciences, University of Southampton, Southampton, UK


Received 17 December 2018. Revision requested 12 February 2019. Accepted 30 April 2019. First published online 12 February 2020.


221–245 elephants are now estimated to remain in Lin- cang, Pu’Er and Xishuangbanna Prefectures in southern Yunnan Province (Zhang et al., 2015). The population is frag- mented into seven poorly connected subpopulations, with only four of these containing .40 individuals (Zhang et al., 2015). Fragmentation has been driven by ongoing human population expansion, rapid land conversion to agri- culture and expanding urbanization (Choudhury et al., 2008). Remnant populations are restricted to herds in small forest fragments within ahuman-dominated landscape (Choudhury et al., 2008). These small isolated populations probably suffer from genetic impoverishment and demo- graphic stochasticity, leading to an increased risk of extinc- tion (Lande, 1993; Frankham, 2003). This study aims to determine the demographic and


social structures of elephants in a remnant population in Nangunhe National Nature Reserve, Lincang Prefecture, situated at the border between China and Myanmar. Previous studies of elephants in Nangunhe have focused


This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Oryx, 2021, 55(3), 473–478 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319000504


lobal elephant populations are declining. All surviving elephant species, the African bush elephant Loxodonta


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