Why did the Komodo Dragon survive the Pleistocene extinctions of the megafauna?


Sometimes exceeding 100 kg in weight, the Komodo dragon Varanus komodoensis is the largest species of lizard in the world (photo Ruchira Somaweera). (b) Large Komodo dragons in modern-day populations depend heavily upon introduced ungulates as prey. This Timor deer (Rusa timorensis) was actively hunted down by an adult Komodo dragon (photos W.K. Fletcher and Donna Baylis). (c) Komodo dragons frequently walk along the beaches at low tide scavenging beach-washed marine items (photo Richard Shine).

A new paper by Shine and Somaweera (2019) seeks to understand why much of the world's terrestrial megafauna went extinct within the last 50,000 years, by looking at the exceptions: large-bodied species that avoided that fate. The Komodo dragon (Varanus komodoensis) is tenfold heavier than almost any other surviving lizard species, it is restricted to small islands, and relies on scavenging as well as predation – attributes that doomed other megafaunal taxa to extinction. How did these giant reptiles persist? The authors suggest that the Komodo dragons' survival reflects general attributes of ectotherms (low energy demands; an ability to reduce mean adult body sizes during resource shortages) coupled with features of varanid biology (behavioural and ecological flexibility that allowed utilization of marine subsidies; salt tolerance), the habitat (a fragmented arid landscape better-suited to reptiles than to humans; and with substantial spatial and temporal variation in rainfall patterns and thus productivity), and the history of hominid colonization (when modern humans arrived, they brought with them novel prey [pigs] that blunted the impacts of hunting and habitat degradation). In short, the surprising persistence of the Komodo dragon is not due to any single unique attribute, but instead reflects a fortunate combination of factors relating to the species, the habitat, and the timeframe and nature of human colonization.

Shine R, Somaweera R. 2019. Last lizard standing: The enigmatic persistence of the Komodo dragon. Global Ecology and Conservation. 2019 Apr 11:e00624.

Comments

Popular Posts