World-first study identifies centipedes as seabird predators

A Phillip Island Centipede (Cormocephalus coynei) consuming a scavenged Günther's Island Gecko (Christinus guentheri). Image: D. Terrington (2019).

An international study led by Monash University scientists has found that giant centipedes, growing up to 23 cm long, are predators of seabirds, suggesting that the arthropod has a key role to play in ecosystem dynamics.

The discovery, based on research on Phillip Island, Norfolk Island, is outlined today in the American Naturalist.

Lead author of the study, professional ecologist and PhD candidate Luke Halpin at the Monash University School of Biological Sciences said the research revealed a novel result.

“There is evidence that large centipedes around the world consume vertebrate animals, but this is the first time that centipedes have been implicated as a major, natural predator of seabirds,” Luke said.

“Our work demonstrates that arthropods can play a leading role in influencing vertebrate reproductive output, and modifying trophic structures and nutrient flow in island ecosystems,” he said.

Phillip Island centipedes are predators of vertebrates including seabird chicks, geckos and skinks.

Because they prey upon animals as large as seabirds, and there are no other predators on the island that routinely prey upon centipedes, they are known as top order predators in this ecosystem.

As a top order predator, the feeding habits of the centipedes directly introduce nutrients to the island that would otherwise be unavailable in the nutrient pool (that is, by hunting seabird chicks).

On the Norfolk Islands Group, South Pacific, the research team monitored the diet and foraging activity of an endemic chilopod, the Phillip Island centipede (Cormocephalus coynei) and used a stable isotope mixing model to estimate the proportions of prey species in centipede diet.

The Phillip Island centipede diet is represented by vertebrate animals (48%) and invertebrates (52%), with 30.5% consisting of lizards including the Lord Howe Island skink (Oligosoma lichenigera) and Günther’s island gecko (Christinus guentheri), 7.9% black-winged petrel (Pterodroma nigripennis) nestlings, and 9.6% marine fishes that are dropped to the forest floor by tree-nesting seabirds.

“What they are eating is predicted by the model we built,” explains Luke.

“But this represents an unusually high proportion of vertebrates in an invertebrate’s diet,” he said.

The research shows that arthropods can increase the flow of marine nutrients in an island ecosystem by preying on the offspring of vertebrates that forage exclusively in pelagic environments.

“We demonstrate how predatory arthropods can exert top-down pressure on vertebrate populations through predation-mediated reductions in reproductive output,” Luke said.

“This could have important consequences for understanding trophic structures on islands and how vertebrate communities are shaped. Perhaps especially so on islands, where arthropod gigantism is common and evolutionary processes have allowed invertebrates to occupy novel niches.”

Co-author Dr Rohan Clarke, a senior lecturer in ecology at the Monash University School of Biological Sciences, said that a giant centipede has a key role to play in shaping a natural system really emphasises the complexity of nature.

“It highlights just how important it is to conserve remaining natural areas so that complex interactions such as this, which ultimately support life on earth, aren’t further disrupted,” Dr Clarke said.

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