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E N V I R O N M EN T WATCH TINY PESTS HAVE A BIG IMPACT BY JEFF COOK M any of our offshore islands are free of predators like possums, rodents and mustelids, but there are new emerging threats, and these are not so easy to see. Argentine ants and rainbow skinks are present on just a few islands so far, but pose a big risk to native birds and insects through both aggression and out-competing the native birds and insects for food and habitat. Rainbow skinks can be found on Rangitoto, Motutapu and Waiheke, while Argentine ants are present on Waiheke, Kawau Island and Great Barrier. Both are well established on the mainland, including at some marinas. "There is a lot of work going on in the Hauraki Gulf to protect our islands from these pests," says Jack Craw, Auckland Regional Council biosecurity Manager. "Organisations like Auckland Council, Department of Conservation and Landcare Research are working together and collaborating with Unitec, the University of Auckland, contractors and volunteers, and we need everyone to get on board with stopping the spread." RAINBOW SKINKS These Australian lizards are prolific breeders, able to reach high population densities in a relatively short time, potentially competing with our native lizard species for food, habitat and space. Masters student Jacqui Wairepo has been working with Auckland Council on surveillance and detection of rainbow skinks in Auckland and the Hauraki Gulf, first as a summer student and more recently as a contractor. Masters student Jacqui Wairepo at She is studying work on rainbow skink surveillance towards her Masters in Conservation Biology at Massey University and her work has taken her around the gulf, including to Kawau Island for her summer studentship in 2011 and since then to Rakino, Rotoroa, Pakatoa and Waiheke. She has also surveyed 11 marinas from Maraetai to Sandspit and nurseries on islands and the mainland. "Nurseries are one of the biggest risk habitats as the gardening material and soil is a favourite habitat for the lizards and many islands source plants from mainland nurseries," says Jacqui. "My work for the council concentrates on presence and absence, establishing where the rainbow skink populations are and the density of these populations." Jacqui first looks at aerial maps for likely terrain and locations such as ferry terminals, areas of disturbance and urbanisation. She then visits a site, performs a visual check and places tracking tunnels, often using bananas as bait, which attract insects and thus hungry lizards. "Tracking tunnels will pick up rainbow skink tracks quite quickly if they are present and also track native species, so you can assess the impacts of the rainbow skinks in that area." If a population is identified, the site is mapped and the council can work on a biosecurity plan for the area. "Through my study I want to look at the impacts of rainbow 54 Professional Skipper May/June 2013 skinks, both on native skink populations and the wider impacts through what they eat and where they live and possible control tools and methods," says Jacqui. "Most people don't realise we even have a pest lizard in New Zealand, so there is also a challenge in raising awareness." ARGENTINE ANTS The most recent Argentine ant discovery in the Hauraki Gulf is on Kawau Island, which is limited to two sites, at Schoolhouse Bay and Vivian Bay. Schoolhouse Bay was treated with Xtinguish bait Argentine ant operation at Vivian Bay on in spring 2012, Kawau in February this year with good results so far, and Vivian Bay underwent a control operation in February this year using Biforce and Biff Ant with follow-up monitoring due soon. "Invasive insects like Argentine ants are a major threat to the values of our offshore islands," says ARC biosecurity manager, Jack Craw. "But we have some great tools at our disposal now too, including a certified Argentine ant detection dog." "We are hopeful of eradication on Kawau Island, and also have a major eradication programme on Great Barrier but we will only succeed if everyone plays their part in checking their gear for pests." WHAT TO DO TO STOP THE SPREAD Both of these pests are small and able to hide easily among equipment and supplies going to islands. "An extra check just before leaving port is essential, as pests can slip on board at marinas and boat ramps if there is a delay between a biosecurity check and departure." "If it takes you half an hour to load your boat, that is plenty of time for stowaway pests to sneak on board or into your gear, and we know there are pest populations around marinas," says Jack. "Both of these pests like similar habitat, so always be particularly vigilant when checking garden material, pot plants, camping gear and building material." Dunking pot plants for at least one minute will send Argentine ants, and skink eggs to the surface. Also, make sure food on board your vessel is stored in tightly sealed containers and waste stored in appropriate rubbish bins. Argentine ants can be difficult to identify so skippers should be keeping their vessels, equipment and cargo completely ant free, as this ensures that no ant species are being transported to and from islands. If you suspect you have seen either of these pests on board or in your gear, the entire shipment should be left behind and the pests reported to Auckland Council Biosecurity 09 301 0101 or the Department of Conservation hotline, 0800 DOC HOT. Keep a sample in a sealed container if possible. For more information, visit www.treasureislands.co.nz