Little to fear: largest lizard predator induces weak defense responses in ungulate prey

Nonconsumptive effects can strongly influence apex predator ecological function. These effects arise because prey often induce costly phenotypic responses to mitigate predation risk. Yet because predator–prey interactions are complex, prey defenses may vary considerably. We investigated if the Komodo dragon (Varanus komodoensis), a reptile apex predator, induced multiscale antipredator responses in key prey, the Rusa deer (Cervus timorensis) and the wild pig (Sus scrofa). To this end, we examined the temporal and spatial partitioning of habitats by predator and prey, determined the size of ungulate groups as a function of risk, and assessed changes in individual behavior of prey individuals exposed to predator kairomones at feeding stations. Komodo dragon, deer, and pig populations exhibited significant, but subtle differences in 3 habitat preferences that otherwise indicated high niche overlap. Komodo dragon predation risk, alongside other commonly considered predictor variables, did not affect deer or pig group size. With the exception of one individual-based vigilance-type behavior in pigs, no other antipredator behavior, including reduced food consumption, significantly varied in the presence of predator odor cue at feeding stations. Overall, our results indicated limited evidence for antipredator behavior and suggested Komodo dragons exert weak nonconsumptive effects of predation in ungulates. However, weak predatory interactions could be beneficial in island ecosystems as it could promote predator–prey coexistence that reduces extinction risk.