Island specific conservation strategies

Evidence for Island specific conservation strategies on Komodo dragons

M Jeri Imansyah,Tim S Jessop, Claudio Ciofi, Deni Purwandana, Achmad Ariefiandy, Heru Rudiharto, Aganto Seno

(Abstract presented in the International Seminar of Biology, Gadjah Mada University, Yogyakarta Indonesia, 7-8 September 2007)

INTRODUCTION

Insular species are mostly susceptible to threatening processes due to limiting environmental factors including habitat loss, harvesting and invasive species because they are isolated and occur on smaller land masses (Burkey, 1995). Komodo dragon (Varanus komodoensis) is an endemic and vulnerable species inhabiting five islands in the Lesser Sunda region, southeastIndonesia. To facilitate implementation of management and conservation strategiesfor Komodo dragons in Komodo National Park, we identified insular differences among four major island populations by examining 1) Komodo dragon population density, 2) Komodo dragon body size, and 3) density of prey species (the Timor deer Cervus timorensis).

MATERIALS AND METHODS

The study was undertaken from 2003 to 2006 across 10 study sites on the islands of Komodo (393.4 km²), Rinca (278.0 km²), Gili Motang (10.3 km²), and Nusa Kode (9.3 km²) within the boundary of Komodo National Park. Capture-mark-recapture techniques were implemented to estimate differences in population density and body size among island Komodo dragon populations. Indices of Timor deer density, the main prey of Komodo dragons, was estimated by implementing pellet group density counts along line transects.

RESULTS AND DISCUSSION

The study showed significant insular divergences in Komodo dragon population density, body size for both SVL and weight, and Timor deer density as its main prey (One way ANOVA F_3,3=120.67, p<0.001;>F3,99=10960.97, p<0.001) name="OLE_LINK4">F_3,99= 6707.63, p<0.001), style="color: black;">F_3,1218=120.67, p<0.001, respectively) (Table 1). Smaller islands showed significantly lower values of these parameters than the larger islands. Timor deer density index was showed significant correlation with Komodo dragon population density (R²=0.635, F_2,202=191.74, P<0.001)>2=0.80, F_2,96=191.74, P<0.001) and weight (R²=0.73, F_2,96=131.05, P<0.001).

The study suggests that there are major divergences in both population (density and body size) and ecological parameter (main prey density) among insular Komodo dragon populations. In particular, the Komodo dragon population on Gili Motang island displayed significant differences in both population size and individual body mass from the other islands. Ciofi & Bruford (1999) showed that the Gili Motang population had the lowest level of genetic diversity compared to other insular populations as a result of limited gene flow and high genetic drift. Low population density, a reduced degree of genetic variation and a shortage of main prey species demand for island-specific conservation strategies for Komodo dragons on Gili Motang. Current management strategies adopted by Komodo National Park authority do not include the Gili Motang Komodo dragon population within the park conservation priorities.. Therefore, management officials should consider design of island specific conservation strategy of Komodo dragon populations in Komodo National Park, particularly for small islands such as Gili Motang.

Table 1. Summary results of Komodo density, body size, and prey density index

	Island	Komodo Density (ind/km2)	Komodo SVL (cm)	Komodo weight (kg)	Deer density (pellet group/ transect)
	Komodo	18.83	142.80	63.93	26.97
	Rinca	30.59	128.80	48.16	20.27
	Gili Motang	13.68	99.41	17.06	5.64
	Nusa Kode	11.80	95.53	15.99	7.81

Figure 1. Correlation between Deer density index and Komodo density

REFERENCES

[1] Burkey, T.V., “Extinction rates in archipelagos: implications for populations in fragmented habitats”, Conservation Biology 9, 527–541. 1995.

[2] Ciofi, C., Bruford, M.W., ”Genetic structure and gene flow among Komodo dragon populations inferred by microsatellite loci analysis”, Molecular Ecology 8, S17–S30.1999.

[3] Jessop, T.S., Madsen, T., Ciofi, C., Imansyah, M.J., Purwandana, D., Rudiharto, H., Arifiandy, A., Phillips, J.A, “Island differences in population size structure and catch per unit effort and their conservation implications for Komodo dragons”, Biological Conservation 135:247-255. 2007.