Demographic status of Komodo dragons populations in Komodo National Park

Biological Conservation (Impact Factor: 3.76). 02/2014; 171. DOI: 10.1016/j.biocon.2014.01.017


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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Available from: Tim S. Jessop, Feb 05, 2014
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    • "Although the high values of F recorded in this study are relative estimates and best evaluated with respect to values recorded in other island populations (Wang 2014), such attributes may lead to higher rates of genetic drift and could allow fi xation of new, mildly deleterious alleles, which in the absence of purging (Wang 2000) could cause mean fi tness to decline rapidly (Lynch et al. 1995). Although the Motang population has persisted despite low genetic variation, small population size and low levels of gene fl ow from other islands (Ciofi et al. 1999), annual surveys indicate a rapidly declining population (Purwandana et al. 2014). Th e Motang population is the result of an isolation event following rising sea levels after the last glacial maximum (Ciofi and Bruford 1999). "
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    ABSTRACT: The population dynamics of island species are considered particularly sensitive to variation in environmental, demographic and/or genetic processes. However, few studies have attempted to evaluate the relative importance of these processes for key vital rates in island endemics. We integrated the results of long-term capture – mark – recapture analysis, prey surveys, habitat quality assessments and molecular analysis to determine the causes of variation in the survival rates of Komodo dragons Varanus komodoensis at 10 sites on four islands in Komodo National Park, Indonesia. Using open population capture – mark – recapture methods, we ranked competing models that considered environmental, ecological, genetic and demographic effects on site-specific Komodo dragon survival rates. Site-specific survival rates ranged from 0.49 (95% CI: 0.33 – 0.68) to 0.92 (0.79 – 0.97) in the 10 study sites. Th e three highest-ranked models (i.e. Δ QAIC c < 2) explained ∼ 70% of variation in Komodo dragon survival rates and identified interactions between inbreeding coefficients, prey biomass density and habitat quality as important explanatory variables. Th ere was evidence of additive effects from ecological and genetic (e.g. inbreeding) processes affecting Komodo dragon survival rates. Our results indicate that maintaining high ungulate prey biomass and habitat quality would enhance the persistence of Komodo dragon populations. Assisted gene fl ow may also increase the genetic and demographic viability of the smaller Komodo dragon populations.
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    • "Finally we considered how changes to current monitoring expenditure (i.e. use of cage trapping and mark recapture methods; Purwandana et al. 2014) could influence alternative conservation actions for this 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.
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    ABSTRACT: Multidisciplinary conservation initiatives are increasingly advocated as best practice for recovering endangered species. The Komodo dragon Varanus komodoensis is the world's largest lizard, of prominent conservation value as an umbrella species for protection of south-east Indonesian ecosystems. Komodo dragons have faced multiple human-related threat processes in the past 30 years and are listed on Appendix I of the Convention on International Trade in Endangered Species of Wild Fauna and Flora, and considered Vulnerable according to the International Union for Conservation of Nature Red List. We report on a protection programme conducted from 2005 to 2012 in the Wae Wuul nature reserve, on the island of Flores, Indonesia. The Wae Wuul ranger post was completely rebuilt, and community awareness and involvement of local people in habitat-protection schemes were regularly and successfully implemented. Local rangers were trained in wildlife-monitoring techniques. Monitoring results indicated that Komodo dragon densities were lower in Wae Wuul than in the adjacent Komodo National Park; however, a relatively high level of genetic diversity was recorded for this population. Ungulate prey showed a relatively stable prey population density. Community-based initiatives and regular wildlife monitoring are crucial to ensure the persistence of Komodo dragons on Flores. The Wae Wuul protection programme is providing several sustainability indicators by which informed management plans can be designed for long-term conservation of Komodo dragons.
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