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Evaluation of three field monitoring-density estimation protocols and their relevance to Komodo dragon conservation

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Abstract

Finding practical ways to robustly estimate abundance or density trends in threatened species is a key facet for effective conservation management. Further identifying less expensive monitoring methods that provide adequate data for robust population density estimates can facilitate increased investment into other conservation initiatives needed for species recovery. Here we evaluated and compared inference-and cost-effectiveness criteria for three field monitoring-density estimation protocols to improve conservation activities for the threatened Komodo dragon (Varanus komodoensis). We undertook line-transect counts, cage trapping and camera monitoring surveys for Komodo dragons at 11 sites within protected areas in Eastern Indonesia to collect data to estimate density using distance sampling methods or the Royle–Nichols abundance induced heterogeneity model. Distance sampling estimates were considered poor due to large confidence intervals, a high coefficient of variation and that false absences were obtained in 45 % of sites where other monitoring methods detected lizards present. The Royle–Nichols model using presence/absence data obtained from cage trapping and camera monitoring produced highly correlated density estimates, obtained similar measures of precision and recorded no false absences in data collation. However because costs associated with camera monitoring were considerably less than cage trapping methods, albeit marginally more expensive than distance sampling, better inference from this method is advocated for ongoing population monitoring of Komodo dragons. Further the cost-savings achieved by adopting this field monitoring method could facilitate increased expenditure on alternative management strategies that could help address current declines in two Komodo dragon populations.

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Acknowledgments

This Research was authorized under a collaborative research memorandum of understanding (MOU) between Indonesian Department of Forest Protection and Nature Conservation (PHKA) and the Komodo Survival Program. Animal experimental ethics committee approval was obtained from the University of Melbourne (under Permit 0911162.1). We thank the many Komodo National Park staff, Balai Besar Konservasi Sumber Daya Alam NTT staff, Komodo Islanders and Flores Islanders for facilitating, and assisting with our field research. Funding was provided through members of the American Zoological Association and European Association of Zoos and Aquaria contributing to the Komodo Species Survival Plan and  Taronga Conservation Society Australia.

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Authors and Affiliations

  1. Komodo Survival Program, Denpasar, Bali, 80223, Indonesia

    Achmad Ariefiandy & Deni Purwandana

  2. Komodo National Park, Labuan Bajo, Flores, 86554, Indonesia

    Aganto Seno

  3. Balai Besar Konservasi Sumber Daya Alam, Kupang, Nusa Tenggara Timur NTT, 85000, Indonesia

    Marliana Chrismiawati

  4. Department of Biology, University of Florence, Sesto Fiorentino, 50019, Florence, Italy

    Claudio Ciofi

  5. Department of Zoology, University of Melbourne, Parkville, VIC, 3010, Australia

    Tim S. Jessop

Authors
  1. Achmad Ariefiandy
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  2. Deni Purwandana
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  3. Aganto Seno
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  4. Marliana Chrismiawati
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  5. Claudio Ciofi
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  6. Tim S. Jessop
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Corresponding author

Correspondence to Tim S. Jessop.

Additional information

Communicated by Indraneil Das.

Appendix

Appendix

See Fig. 2 and Tables 3, 4, 5, 6

Table 3 Annual field monitoring costs for three field survey method used to obtain data for estimating Komodo dragon density at 11 sites in protected areas in Eastern Indonesia
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Table 4 Transect length, number of clusters and mean (± SE) cluster sizes observed during distance sampling of Komodo dragons at 11 sites in Komodo National Park and Wae Wuul Nature Reserve, Indonesia
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Table 5 Ranking of Royle–Nichols abundance induced heterogeneity model used to estimate λ (average abundance per site) and r (species detectability) using cage traps (a) and camera stations (b)
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Table 6 Estimates of Komodo dragon detection probability (r) derived from the top ranked Royle–Nichols model obtained from cage trapping and camera monitoring surveys
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Ariefiandy, A., Purwandana, D., Seno, A. et al. Evaluation of three field monitoring-density estimation protocols and their relevance to Komodo dragon conservation. Biodivers Conserv 23, 2473–2490 (2014). https://doi.org/10.1007/s10531-014-0733-3

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  • DOI: https://doi.org/10.1007/s10531-014-0733-3

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