Demographic status of Komodo dragons populations in Komodo National Park

Biological Conservation (Impact Factor: 4.04). 02/2014; 171. DOI: 10.1016/j.biocon.2014.01.017

ABSTRACT The Komodo dragon (Varanus komodoensis) is the world's largest lizard and endemic to five islands in Eastern Indonesia. The current management of this species is limited by a paucity of demographic infor-mation needed to determine key threats to population persistence. Here we conducted a large scale trap-ping study to estimate demographic parameters including population growth rates, survival and abundance for four Komodo dragon island populations in Komodo National Park. A combined capture mark recapture framework was used to estimate demographic parameters from 925 marked individuals monitored between 2003 and 2012. Island specific estimates of population growth, survival and abun-dance, were estimated using open population capture–recapture analyses. Large island populations are characterised by near or stable population growth (i.e. k $ 1), whilst one small island population (Gili Motang) appeared to be in decline (k = 0.68 ± 0.09). Population differences were evident in apparent sur-vival, with estimates being higher for populations on the two large islands compared to the two small islands. We extrapolated island specific population abundance estimates (considerate of species habitat use) to produce a total population abundance estimate of 2448 (95% CI: 2067–2922) Komodo dragons in Komodo National Park. Our results suggest that park managers must consider island specific population dynamics for managing and recovering current populations. Moreover understanding what demographic, environmental or genetic processes act independently, or in combination, to cause variation in current population dynamics is the next key step necessary to better conserve this iconic species.

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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 identi-fying 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-effec-tiveness criteria for three field monitoring-density estimation protocols to improve con-servation 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 het-erogeneity model. Distance sampling estimates were considered poor due to large confi-dence 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 Communicated by Indraneil Das.
    Biodiversity and Conservation 07/2014; 23(10). DOI:10.1007/s10531-014-0733-3 · 2.07 Impact Factor