What determines Komodo dragon survival?

Submitted by editor on 29 September 2015. Get the paper!
A Komodo dragon walks on the beach in Komodo National Park, Indonesia. (Photograph by Achmad Ariefiandy).


By Tim Jessop, Deni Purwandana, Achmad Ariefiandy and Claudio Ciofi.


Across islands, animals may experience marked local environmental variation that along with density or genetic related processes can dramatically influence population vital rates.  However, few studies have attempted to evaluate the relative importance of these different processes on vital rates across multiple island populations.

The Komodo dragon (Varanus komodoensis) is the world’s largest lizard and persists on 5 islands in eastern Indonesia.  Four populations occur in Komodo National Park, the key conservation area for this species. However, because islands vary considerably in habitat and especially prey resources, an artefact of different island areas, and that some dragon populations have been historically isolated for millennia, multiple processes could influence lizard vital rates.

In this decade long field study, we integrated the results of capture–mark–recapture analysis, prey surveys, habitat quality assessments and molecular analysis to determine the causes of variation in survival rates of Komodo dragons at 10 sites on four islands in Komodo National Park. Across these sites, estimated survival rates varied nearly two fold. Three processes, prey biomass density, habitat quality and inbreeding coefficients explained considerable variation in Komodo dragon survival rates. These effects were most pronounced for small island populations where survival was substantially lower than that of large island populations.  Furthermore, as theory predicts there was evidence for an additive negative effect from ecological and genetic processes acting on Komodo dragon survival rates.

Our results suggest that to adequately conserve Komodo dragon populations, park managers must ensure that high ungulate prey densities and habitat quality are maintained.  Additionally, assisted gene flow may be necessary to increase the genetic and demographic viability of the small island Komodo dragon populations.