On small Phillip Island, part of the Norfolk Island group in the South Pacific, the Phillip Island centipede (Cormocephalus coynei) the population can kill and eat up to 3,700 seabird chicks each year.
And that is completely natural. This unique creature endemic to Phillip Island has a diet that consists of an unusually large proportion of vertebrate animals, including seabird chicks.
Phillip Island from the Norfolk Island group, with a valley of iconic Norfolk Island pines. (Luke Halpin)
As large marine predators, seabirds usually sit at the top of the food chain. But our new study, published in The American Naturalist, shows that this is not always the case.
We show how large predatory arthropods can play an important role in the trophic networks of island ecosystems. And Phillip Island’s centipede gets it thanks to its very varied diet.
A well-armed predator stirs the night
This centipede can grow up to almost a foot (or 30.5 cm) in length. It is armed with a powerful venom embedded in two clamp-like appendages called “forceps,” which it uses to immobilize its prey. Its body is protected by shielded plates in the form of shield that cover each one with the numerous segments that form their length.
Phillip Island centipede and black-winged petrel. (Luke Halpin, author provided)
On warm, humid nights, these strictly nocturnal arthropods hunt through thick leaves, navigating a maze of seabird dens nestled in the forest floor. A wandering centipede will use its two ultra-sensitive antennas to navigate while looking for prey.
The centipede hunts a wide range of unexpectedly varied quarries, from crickets to seabird chicks, geckos and scavengers. He even hunts fish, dropped by seabirds called black noddies (
Anous minute) that make nests in the trees above.
A frightening discovery
Shortly after beginning our research on the ecology of Phillip Island seabirds, we discovered black-winged petrel chicks (Pterodroma nigripennis) fell prey to the Phillip Island centipede.
We knew we needed to dig deeper into the research, so we set out to unravel the mystery of the dietary habits of this great arthropod.
Black-winged Petrel Chick just before being weighed down on Phillip Island. (Trudy Chatwin)
To find out what these centipedes ate, we studied their feeding activities at night and recorded the species of prey they were targeting. We also monitored the petrel chicks in their nest nests every few days, for months.
Eventually, we began to see patterns of constant injury among the chicks that died. We even witnessed a centipede attacking and eating a chick.
From the predation rates we observed, we calculated that the Phillip Island centipede population can kill and eat between 2,109 and 3,724 petrel chicks each year. Black-winged petrels – of which there are up to 19,000 breeding pairs on the island – appear to be resistant to this level of predation.
And the predation of black-winged petri dishes by Phillip Island centipedes is a totally natural predator-prey relationship. By predating vertebrates, centipedes trap nutrients that seabirds come from the ocean and distribute them across the island.
In a sense, they have taken the place (or ecological niche) of predatory mammals, absent from the island.
Luke Halpin tracks black-winged petrel chicks on Phillip Island. (Trudy Chatwin)
Restoration and recovery
Until a few decades ago, Phillip Island’s centipede was very scarce. In fact, it was only formally described as a species in 1984.
After intensive research in 1980, only a few small individuals were found. The rarity of the species at that time was probably due to severely degraded habitats caused by pigs, goats and rabbits introduced by humans to the island.
The removal of these invasive pests allowed black-winged petrels to colonize. Its population has exploded since then and they are now the most abundant of the 13 species of seabirds that breed on Phillip Island.
They provide a source of high quality food for the Phillip Island centipede and have therefore likely helped in the recovery of the centipede population.
Ancient bone deposits on the ground suggest that before the arrival of the black-winged petrel, there were a large number of other small seabird species nesting in the nests on Phillip Island. It is likely that the Phillip Island centipede has also preyed on these seabirds.
Now, thanks to conservation efforts in Norfolk Island National Park, the island’s forest is regenerating alongside endemic species such as the centipede, as well as critically endangered Phillip Island hibiscus (Hibiscus insularis).
As a driver of nutrient transfer, the persistence of the Phillip Island centipede (and its healthy appetite) could be key to the recovery of the island’s ecosystem. But we will have to do more research to better understand the intricate links of this bustling food web.
Luke Halpin, ecologist, Monash University; Rohan Clarke, director of the Monash Drone Discovery Platform and senior professor of ecology, Monash Universityand Rowan Mott, biologist, Monash University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
