Our Changing World for Thursday 13 February 2014
Lord Howe Island’s Proposed Rat Eradication
Vew of Lord Howe Island from the summit of Mount Gower, and a pair of white terns (images: A. Ballance)
New Zealanders are world-leaders when it comes to eradicating unwanted introduced pests from islands. Our knowledge and experience has been exported around the world, and now over 300 islands world-wide have had successful eradication projects. Until now these eradications have mostly been on uninhabited islands – that is, islands without a permanent community. Now, there is talk in New Zealand of aiming to eradicate various pests, usually mammalian predators, from larger inhabited islands such as Stewart Island or Great Barrier Island, and perhaps even mainland New Zealand in the future.
Lord Howe Island in Australia is already several steps ahead of New Zealand, and could become the first inhabited island in the world to make itself rodent-free. This 1500 hectare island lies 700 kilometres north-east of Sydney but has strong biological ties with New Zealand, and geographically sits on the sunken continent of Zealandia. With a permanent community of 350 people, it makes its money from eco-tourism, and it has been discussing an eradication plan for ship rats and mice since the early 2000s. It has already eradicated feral goats and pigs, and got rid of both feral and domestic cats. In 2012 the Federal Government of Australia and the Government of New South Wales jointly came up with Australian$9-million for a one-off aerial rodent eradication programme.
Alison Ballance visited Lord Howe Island recently to find out if it could offer any lessons for New Zealand about eradications on inhabited islands. What she found was a divided community – while everyone she spoke to agreed that a rodent eradication is a great idea in principle, many are concerned about the aerial nature of the eradication, the use of the anti-coagulant brodifacoum in a wide-scale once-off operation and what they perceive as a lack of communication from the Lord Howe Island Board. While none of the opponents of the plan wanted to speak on record, Alison talked with other islanders who explained the island’s history of introduced species, the extinctions that have resulted and their opinions as to why the proposed eradication is a good idea. Barney Nichols is deputy chair of the Lord Howe Island Board; Bill Shead owns Arajilla Retreat; naturalist Dean Hiscox owns Lord Howe Island Environmental Tours; naturalist Ian Hutton is Director of the Lord Howe Island Museum; and New Zealander Peter McClelland is the Lord Howe Island Rodent Eradication Project Manager.
And the key lesson for New Zealand? That the first step in any proposed eradication is to get the community fully engaged and behind the idea.
Anton Mather with some seaweed (image: University of Canterbury)
Commercial glues often fail when used underwater, but Anton Mather from the University of Canterbury is testing New Zealand coastline seaweed to see if a naturally inspired adhesive can be developed.
In particular, Anton is looking at the adhesive created by newborn Durvillaea antarctica and Hormosira banksii. Using a flow channel, he is examining the adhesion of cells across different substrates, including glass, polished stainless steel and unpolished stainless steel. He explains to Ruth Beran how he creates the baby kelp, and that he has found that a settling time of twelve hours post-fertilisation is needed before the newborn seaweed really sticks. In the future he hopes to use enzymes to analyse the composition of the seaweed glue and discover which elements are responsible for adhesion.
Jumping Spider Vision
A 'mosquito terminator’ jumping spider (Evarcha culicivora), from east Africa, holds a mosquito it has just caught; a number of the spider's eight eyes are visible. These little spiders are able to catch prey much larger than themselves (right) (images: Robert Jackson)
Ximena Nelson leads research into vision in jumping spiders at the University of Canterbury, which is known world-wide for its spider research. Alison Ballance joins her in the Spider Lab, to meet some of the spider species she works with, and then watches as an East Africa ‘Mosquito terminator’, more properly known as Evarcha culicivora, is given an ‘eyesight test’. These little jumping spiders hunt Anopheles mosquitoes, which are vectors for malaria. Spiders have eight eyes, and rather than move their eyes they turn their whole body towards an object of interest, and when they recognise something as food (even if it is an abstract representation of a mosquito) they will jump on it, which makes them ideal lab subjects.
By projecting life-sized images of often quite abstract mosquitoes onto a miniature movie screen Ximena and her team have been able to work out that the spiders can differentiate male from female mosquitoes, Anopheles from Culex mosquitoes, and she explains they’ve worked out that the spiders recognise the angles of the legs from the body.
Above: this jumping spider is suspended from a thread while it undergoes a vision test; the spider can't turn its body to look at objects, but instead it rotates the light polystyrene ball it is holding, which allows researchers such as student Amber Melrose to see what it is looking at (image: Daniel Zurak)