Hauturu – Spineless wonders

I have written about what a haven Te Hauturu-o-Toi is for native birds, plants and reptiles. It is also a haven for over 500 of our native invertebrates and that is only the ones that have been found and identified there. There could well be that many again to be discovered, even species new to science.

Invertebrates have no vertebrae or bones; their shape is usually held by an exoskeleton or outer frame. The invertebrate family includes insects, spiders, snails and caterpillars. They are an essential part of any ecosystem and are found everywhere from the ocean to alpine peaks. They carry out many important roles, including providing a food source for insect-feeding birds, reptiles, fish and other insects. They pollinate flowers and break down decaying matter, thus returning nutrients to the soil to be reused. They are part of one of nature’s many self-sustaining cycles. They range in size from the world’s heaviest insect, the wetapunga, to tiny creatures requiring magnifying lenses to be seen.

Most of the invertebrates found on Hauturu would have been present on the nearby mainland until man arrived with accompanying pests and started removing the forest cover. The giant wetapunga was known to be present in the north of New Zealand and on Great Barrier/Aotea. Hauturu was its last remaining stronghold and even there it was struggling until kiore (Polynesian rat) were removed in 2004. Now they are thriving and new populations have been set up on other Hauraki Gulf islands thanks to Auckland Zoo’s breeding programme. Other “giants” found on Hauturu are the giant earthworm that can reach over a metre in length and a giant predatory centipede. Both of these are present in isolated spots on the mainland.

It is thought that moths play an important role pollinating plants and most moths are night-time creatures. This explains why many of New Zealand’s flowering trees have white flowers so they stand out at night. It was fascinating to be on Hauturu one summer evening watching giant puriri moths attracted to lights at the ranger’s house, playing their part in nature’s cycle of life, as a morepork (ruru) swooped and grabbed some for his dinner.

When the kiore were removed from the island it was noted that the German and common wasps that had been present on the island for several decades were disappearing. Now none have been observed for several years. No-one is quite sure what the correlation is. Researchers are studying this phenomenon at the moment.

Aquatic insects are great indicators of the health of streams. Hauturu’s streams are pristine so it has its share of aquatic insects. They need to be species that can survive the constantly changing water levels and flows.

Invertebrates have such an important role to play in any ecosystem that when we consider restoration or conservation it is important to include them in our plans.

Lyn Wade, Little Barrier Island Supporters Trust
www.littlebarrierisland.org.nz