Deriving a population estimate for Eld’s deer (Rucervus eldii siamensis) in Siem Pang Wildlife Sanctuary, Cambodia

Paul Meek; Rachel Ladd; Jonathan C. Eames; Luke K.-P. Leung

doi:10.1071/PC25029

RESEARCH ARTICLE (Open Access)

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Deriving a population estimate for Eld’s deer (Rucervus eldii siamensis) in Siem Pang Wildlife Sanctuary, Cambodia

Paul Meek

^A ^B ^* , Rachel Ladd

^A , Jonathan C. Eames ^C and Luke K.-P. Leung ^A ^D

+ Author Affiliations

- Author Affiliations

^A School of Agriculture and Food Sciences, The University of Queensland, Gatton, Qld 4343, Australia.

^B Vertebrate Pest Research Unit, NSW Department of Primary Industries and Regional Development, PO Box 350, Coffs Harbour, NSW 2450, Australia.

^C Rising Phoenix Co, Ltd., 111 Preah Norodom Boulevard (41), Sangkat Chakto Mukh, Phnom Penh 120207, Cambodia.

^D Rodent Testing Centre, Gatton, Qld 4343, Australia.

^* Correspondence to: paul.meek@dpi.nsw.gov.au

Handling Editor: Mike Calver

Pacific Conservation Biology 31, PC25029 https://doi.org/10.1071/PC25029

Submitted: 11 April 2025 Accepted: 15 June 2025 Published: 1 July 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

Eld’s deer (Rucervus eldii) was once widely distributed across Southeast Asia but is now endangered. The strong hold of the subspecies R. e. siamensis is largely restricted to north and east Cambodia, with only small, spatially isolated populations known to occur.

Aims

To assess if camera traps and spatial capture–recapture methodology can estimate population size of Eld’s deer in Siem Pang Wildlife Sanctuary (SMWS).

Methods

Infra-red and white flash camera traps were set at 83 grid-point locations (83 km²) over a 5-month sampling period and used a Spatially Explicit Capture Recapture (SECR) model to estimate population size, relying on natural markings to identify males and using sex ratios to extrapolate a population estimate.

Key results

We estimated the number of Eld’s deer in SMWS to be 272 (95% CI: 169–435). We affirmed that white flash camera traps are advantageous in identifying individuals without significantly affecting detection probability.

Conclusions

Monitoring the small and difficult to detect subpopulations of R. e. siamensis is challenging. Camera traps can be used although there are challenges to resolve when using the SECR model that can be improved by using white flash cameras to improve the identification of individuals, and assisted with sex and age determination.

Implications

The SPWS population may potentially be the largest of the R. e. siamensis subspecies in Southeast Asia and it is therefore of critical conservation importance that long term camera trap monitoring is established.

Keywords: camera trapping, conservation practice, monitoring, population estimation, SECR, sub-species, threatened species, white flash.

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