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Researchers find key role of predatory arthropods in nutrient availability on islands

ResearchEcology lab member Luke Halpin led a recent paper in The American Naturalist, documenting the importance of a large predacious arthropod's habits in structuring trophic dynamics on isolated Phillip Island in the Norfolk Islands Group.

Though Phillip Island Centipedes are now relatively abundant, they were extremely rare in the 1980s due to habitat degradation by introduced pigs, goats, and rabbits. After recording previously undescribed instances of black-winged petrel nestlings falling prey to Phillip Island centipedes, Luke and Honours student Daniel Terrington investigated their diet and foraging activity, discovering that these predatory arthropods likely play an important role in the Phillip Island food web because of their highly varied diet. Not only do these centipedes prey on and consume between 2,109 and 3,724 black-winged petrel nestlings each year, they also consume crickets, geckos, skinks, and even fish dropped from black noddy nests.

Phillip Island centipedes occupy an important ecological niche that might otherwise have been occupied by mammalian predators, as is the case with many island ecosystems that are depauperate of mammals. By preying on a variety of vertebrates Phillip Island centipedes likely make available and distribute marine derived nutrients that would otherwise be unavailable in this system.

“Because of the centipede’s role in driving nutrient transfer, areas of the island with higher densities of centipedes might recover faster than areas that are degraded,” explains Luke. “This could be important for recovery of a variety of critically endangered species on Phillip Island, many of which are endemic and found nowhere else on Earth.”

Despite the fact the centipedes are the main cause of nesting failure for black-winged petrels, the petrel population continues to grow and appears resilient to centipede predation. This, however, does raise the prospect for conservation concerns elsewhere, as innovative approaches may be necessary in disturbed systems where predatory arthropods may interact with prey of conservation importance.

 

Photo by Luke Halpin. Please note that there is some perspective distortion in this photo. 

 

 

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