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Nicholas Carlile, Research Scientist with the NSW Office of Environment and Heritage, looks at the biogeography of Lord Howe Island, a small island group which is home to some 100 endemic plant species (four genera of which are found nowhere else in the world) as well as invertebrate species which are associated with such endemic isolation., the Lord Howe Island phasmid (stick insect) being the most noted of these. The Lord Howe Island wood-feeding cockroach is a far less glamorous endangered invertebrate, one which does not live up to its name as it doesn’t feed on wood but was documented living in such habitats. It is four cm in length, built like a tank and was once widespread throughout the island group.
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| Wood-feeding Cockroaches in cutgrass on Roach Island: The name wood-feeding was certainly found to be a misnomer as the beasties were found under leaf-litter, rocks and artificial housing made of cardboard.
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The arrival of rats and mice on the mainland spelt their demise on the mainland but they have since been sighted on smaller islands like Blackburn Island encompassed within the shallow lagoon, where Nicholas has had a chance to study them. They do live under rocks and such but spend a lot of time burrowing some three centimetres under the surface soil, performing a soil conditioning role much like worms in that it increases its organic matter. When they did occur on the main island they were probably a significant part of the food supply for the Lord Howe Island woodhen (another endangered species on the road to recovery).
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| Blackburn from north: Blackburn Island, within the Lord Howe Island lagoon, proved to hold a large population. Under the main vegetative canopy of the large Banyan Fig was approximately 10,000 Wood-feeding cockroaches.
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The research that Nicholas and his colleagues is doing is part of the Save Our Species program at OEH, which Nicholas coordinates as part of his role as the Islands' Species Project Coordinator. The eradication of rats and mice on the main island is meant to commence on 2015, a future date that allows time to convince the local community that there will be no problems with the water or soil. The Lord Howe Island Board that controls the funding looking at improving community contacts to avoid any adverse reactions from the community. What is proposed is a one off large baiting program using some 40 tons of bait but with residential areas and their environs hand-baited and the endemic wildlife like woodhens and currawongs quarantined from the effects, hence the community concerns about drinking water and domestic stock.
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| Tracking Thread attachment: To determine their movements for a mark-recapture study Wood-feeding cockroaches were temporarily fitted with brilliant-coloured polyester threads. Following their nocturnal movement showed they were ‘locals’ in the study area, providing a huge population at some sites.
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In terms of the cockroach, it is hoped that they will be introduced back onto the mainland once the eradication has been successful. Unlike introduced cockroaches that infest houses, these endemic species will remain in the wild. They will not only provide a good meal for the woodhen but also, more importantly, condition the soils within the forests here, increasing native species resilliance to disturbance from alien plants and stocastic events such as wind storms and drought. Such projects are not short term as they seek to uncover the secrets to restoring environmental balances that have only been studied for a relatively short time. That is why the focus on a cockroach becomes an important part of the wide ranging strategy that includes the reintroduction of species along with addressing the decline of others.
It seems Lord Howe Island is home to more than one balancing act.
Nicholas Carlile was interviewed by Ruby Vincent for A Question of Balance. Images from Nicholas Carlile. Summary text by Victor Barry September 2013.
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