ISLAND MAGIC

Forest and Bird, Issue 268, 1 May 1993, Unnumbered Page

ISLAND MAGIC

TIM HIGHAM

New Zealand has produced its own special suite of plants and animals. This is only one instance of how the isolation of islands results in the evolution of weird, wonderful and

different organisms.

reports on how making a documentary on the Pacific Islands gave one film maker new insights into the evolution of life in this country.

" ORKING on Islands, TVNZ’s recent twopart documentary on the natural history of the Pacific, changed director-producer : z Rod Morris’s perception of New Zealand. The animals and plants he observed resulting from other islands’ isolation helped him appreciate the kind of powerful evolutionary forces that shaped New Zealand’s own fauna and flora. "Those forces are ghosts — long gone — and we have to recognise them through clues that are remote, rare and difficult to access," he says. Two years’ researching and filming Islands gave Morris a unique and privileged overview into natural history and evolution in the Pacific. The former Wildlife Service officer and co-author of Wild South: Saving New Zealand’s Endangered Birds, has plans to work on another popular book based on his Islands insights. "‘I just need a bit more of a handle on how our things fit together — the fish, insects, amphibians and reptiles; not just the rare birds." Morris says some of the jigsaw pieces are starting to be put in place. It is argued by many scientists, for example, that New Zealand’s many divaricating plants are an evolutionary response to moa browsing. A springy bush with its small leaves hidden inside a maze of fibrous stems offers resistance and little sustenance to large, strong-beaked, browsing birds. Some

plants like kowhai, lancewood and matai change from a juvenile divaricating form once above the browsing height of moa. In Indonesia, Morris gained an insight into another long-gone evolutionary process while filming Komodo dragons, three-metre long monitor lizards capable of killing and feeding on adult deer. New Zealand, Morris says, had its Komodo dragon equivalent. The extinct giant eagle, Harpagomis, was the supreme predator of these islands, and in that role shaped the way other animals evolved. Probably Harpagomis was a wait-and-pounce killer: sitting in trees usually near the edge of forest, picking its prey with keen eyesight, swooping down and striking with awesome power. With falcons and goshawks also hunting from above, it made a lot of sense for smaller birds to move about the forest floor and avoid daylight. "The kiwi and kakapo didn’t happen out of apathy and general degeneracy," Morris says. Such theories he labels as "continental arrogance". New Zealand’s fauna was actively selected for — under pressures exactly the opposite to those created by ground-hunting, smellsensitive mammalian predators. Today with only the wreckage of our avifauna left we have to think laterally to try and work out the factors that once shaped it, Morris says. Before the arrival of humans on the Pacific Islands, new immigrants could arrive only by sea or wind dispersal. With up to 4,000 km of water to cross it was a lottery, for which some groups of plants and animals were better suited. The red-crowned parakeet, Cyanoramphus, has colonised Pacific Islands from the subantarctic to the tropics and successfully adapted to the different foods available on each. While the subspecies on most islands eat seeds, nectar, flowers and leaves, on Macauley Island in the Kermadecs the parakeet eats limpets off coastal rocks.

Parakeets and penguins seem unlikely bedfellows — but on New Zealand’s subantaractic Antipodes Island these two very different birds are well acquainted. Spilt food, guano, flies and carcasses provide plenty of pickings for Reischek’s parakeets, a subspecies of red-crowned parakeet, which forage around the edges of the raucous erect-crested penguin colonies.

| RESH ARRIVALS have to learn 4 new tricks and whole ecosystems _ © can develop fresh ways of functioning, like the reptile-dominated forests of the Poor Knights Islands. Here geckos and skinks have become the "birds and bees" of the forest through their pollinating and dispersal roles. Small lizards are also preyed upon by giant centipedes which grow as long as 25 cms. In Hawaii Morris filmed a species of looper caterpillar, a most unlikely carnivore. But because of the under-represen-tation of spiders and ants on the island, the caterpillar was able to evolve a taste for insects and an effective ambush hunting technique. Since ants and spiders have flooded into Hawaii with humans, looper caterpillars have been restricted by competition and predation to higher areas. Similarly, in New Zealand, some native invertebrate populations have been decimated by new immigrants such as wasps. Islands operate as species factories. With different selection pressures from those on continents, new arrivals can evolve in hitherto unimagined ways. In the Solomon Islands i. Reo)

Morris filmed a giant skink, Corucia zebrina, which evolved over time from a small, fast-moving insectivore to a large, plodding, tree-dwelling, fruit-eater, complete with prehensile [grasping] tail. "Tt has become the reptile equivalent of a monkey," says Morris. The skink is also involved in an unusual partnership, often sleeping among fruit bats and benefiting from the mammals’ warmth. In Hawaii

unspectacular finch and herb plant ancestors co-evolved into a fantastic array of lobelia flowers and specialised nectar eating birds. Morris wonders what variations of beak shapes in New Zealand’s wattkebird family, which includes the saddleback,

kokako and extinct huia, were lost in the distant past. The different shapes of male and female huia beaks — enabling them to exploit different food sources — he describes as an example of "island magic". "To look at the moa, dodo and Komodo dragon is to realise the power of Islands," says Morris. Their downfall has only come since humans harnessed the sea and wind and became the third agent of species dispersal. Our carry-bag of predatory and competitive ground-dwelling mammals — whose previous absence in New Zealand allowed giant, flightless crickets (weta), singing bats, and dancing night parrots to evolve — is now pressuring such remarkable animals to extinction. While filming Islands Morris visited Easter Island and observed the statues of a culture that exploited the environment to such an extent it destroyed itself: Such shameful history need not be repeated he hopes. Since cultures are also capable of change there is the opportunity to learn from our mistakes. American biologist Jared Diamond has described New Zealand "as the closest we can come to studying evolution on another planet"’. It is essential, Morris says, that we save those species and ecosystems that have practised island magic.

Tim Higham is a journalist specialising in natural history. He works for the Department of Conservation in Southland.