Ecological allometries and niche use dynamics across Komodo dragon ontogeny

Abstract

Ontogenetic allometries in ecological habits and niche use are key responses by which individuals maximize lifetime fitness. Moreover, such allometries have significant implications for how individuals influence population and community dynamics. Here, we examined how body size variation in Komodo dragons (Varanus komodoensis) influenced ecological allometries in their: (1) prey size preference, (2) daily movement rates, (3) home range area, and (4) subsequent niche use across ontogeny. With increased body mass, Komodo dragons increased prey size with a dramatic switch from small (≤10 kg) to large prey (≥50 kg) in lizards heavier than 20 kg. Rates of foraging movement were described by a non-linear concave down response with lizard increasing hourly movement rates up until ∼20 kg body mass before decreasing daily movement suggesting reduced foraging effort in larger lizards. In contrast, home range area exhibited a sigmoid response with increased body mass. Intrapopulation ecological niche use and overlap were also strongly structured by body size. Thus, ontogenetic allometries suggest Komodo dragon's transition from a highly active foraging mode exploiting small prey through to a less active sit and wait feeding strategy focused on killing large ungulates. Further, our results suggest that as body size increases across ontogeny, the Komodo dragon exhibited marked ontogenetic niche shifts that enabled it to function as an entire vertebrate predator guild by exploiting prey across multiple trophic levels.

A high-resolution, chromosome-assigned Komodo dragon genome reveals adaptations in the cardiovascular, muscular, and chemosensory systems of monitor lizards

“…This sensory apparatus allows Komodo dragons to perceive chemicals from the environment for a variety of social and ecological activities, including kin recognition, mate choice 50,51 , predator avoidance 52,53 , hunting prey 54,55 , and for locating and tracking injured or dead prey. Komodo dragons are unusual as they adopt both foraging tactics across ontogeny with smaller juveniles preferring active foraging for small prey and large adult dragons targeting larger ungulate prey via ambush predation 10 . However, retention of a highly effective lingual-vomeronasal system across ontogeny seems likely, given the exceptional capacity for Komodo dragons of all sizes to locate injured or dead prey.…”

“…As the largest extant lizard species, Komodo dragons can grow to 3 meters in length and run at speeds of up to 20 kilometers miles per hour, which allows them to hunt large prey such as deer and boar in their native Indonesia 8 . Komodo dragons have a higher metabolism than predicted by allometric scaling relationships for varanid lizards 9 , which helps explains their extraordinary capacity for daily movement to locate prey 10 . Their ability to locate injured or dead prey through scent tracking over several kilometers is enabled by a powerful olfactory system 8 .…”

The Arnold Berliner Award 2017

“…1), in recognition of his research article on the Komodo dragon (Varanus komodoensis) published in The Science of Nature in 2016 (Purwandana et al 2016). The study is a contribution to the Komodo Survival Program, a long-term protection programme of this enigmatic lizard.…”

An investigation of the evolution of the anguimorph lizard venom system

“…In recent history deer and water buffalo were also introduced on the islands, and now oras occupy a novel ecosystem, with their potential prey consisting of feral pigs, deer and buffalo. This situation has led to a unique ecological position for the Komodo Dragon, enabling it to function as an entire vertebrate predator guild, by going through rapid ontogenetic niche shifts from preying on relatively small arthropods as a juvenile to big ungulate mammals as an adult (Purwandana et al, 2016). While previously the long-lasting effects of ora's bites were largely attributed to pathogenic bacteria this has since been suggested to be misleading as no pathogenic oral flora was recovered from V. komodoensis saliva or gingiva that would set it apart from any other carnivorous animal (Goldstein et al, 2013).…”

“…That might be the reason why varanid lizards tend to occupy any carnivorous niche the conditions allow for and only cold climate and carnivorous placental mammals can hinder their progress. Some monitors function as an entire predator guild, undergoing an ontogenetic niche shift from being strictly arboreal in juvenile stage all the way to strictly terrestrial when they are adults (Purwandana et al, 2016). At the same time, monitor lizards also scavenge a lot -from carrion to even fruit in some species .…”