Aotea – island of lizards
by Halema Jamieson (Ecologist/Herpetologist)
When we think of reptiles we usually think of warm tropical places like Australia and the Pacific islands. Remarkably then, New Zealand with a predominantly temperate climate has over 100 species of native lizard.
Over 75% of these species are considered threatened or at risk. Many species are now completely absent from the main islands of New Zealand and confined to offshore islands or mainland sanctuaries. This drastic decline has been due to habitat destruction and the ongoing effects of introduced mammalian predators like cats, rats, mice and mustelids.
High lizard diversity
Today, Aotea Great Barrier is among a few small areas of New Zealand with a high diversity of native lizards. Despite losing at least three species and the tuatara (NOT a lizard), the island is still home to an impressive 13 native lizard species (five gecko and eight skink) (Box 1). Some of these species are extinct on the mainland, and for others, Aotea Great Barrier is one of only a handful of places where these animals still exist on the planet. And their future is not secure. Ongoing predation from cats, pigs and rodents (ship rats, kiore, and mice) puts constant pressure on remaining populations, and over 85% of the island’s species are listed in the latest New Zealand Threatened Species classifications1.
Everything eats lizards
The sad fact is that everything eats lizards. The presence of introduced animals plays a large part in their continued survival on Aotea. Rodents are especially bad and have been implicated in the extermination of numerous species from large parts of their former ranges. Although mice, ship rats and kiore are still on Aotea, the largest rat in New Zealand, the Norway rat is not known to be on the island. Neither are hedgehog, possum or any of the mustelid family (stoats, weasels, ferrets).
The introduction of any of these predators would spell disaster for most of the island’s remaining wildlife (lizards, birds, frogs and bats)2.
...over 85% of the island’s [lizard] species are listed in the latest New Zealand Threatened Species classifications...
Lizards play an important role in the functioning of native ecosystems. They are tiny predators eating insects and other invertebrates, important food for native birds like ruru/morepork and kotare/kingfisher, pollinators and seed dispersers to many native plants through their consumption of nectar and fruits. It is vital that they survive.
The continued existence of Aotea’s unique lizard fauna will require ongoing vigilance, and a commitment to reducing the pressure of predators on these often forgotten element of New Zealand’s indigenous fauna. Our native lizards need your help!
Aotea’s fabulous native lizards
Many lizard species considered to be very rare, or no longer found on the mainland, can be found on Aotea - some of them are record holders!
Photographs: H Jamieson unless stated.
New Zealand’s longest lizard— Chevron skink/Niho taniwha (Oligosoma homolonotum) Nationally Vulnerable: Can be over 30cm long and characterised by the chevron-like markings down its back and a ‘tear-drop’ pattern under each eye. Extinct on the mainland and now found only on Aotea and Hauturu (Little Barrier Island). With almost mythical qualities, is best known from Aotea where they are often brought in by cats, or found squashed on the road.
Forest gecko (Mokopirirakau granulatus) At Risk – Declining: Not often seen although still hanging on in forest areas where rats are controlled. Used to be common on the mainland.
Moko skink (Oligosma moco) At Risk: Very rare on the mainland and mostly confined to islands. Does not do well in the presence of rats or cats.
Ornate skink (Oligosoma ornatum) At Risk-Declining: Found on Aotea amongst leaf litter and often brought inside by cats. Confused with the chevron skink.
Auckland green gecko/elegant gecko (Naultinus elegans) At Risk – Declining: Bright green like Kermit the frog. Very rare on Aotea with very few sightings in the last 20 years. Was once common in Auckland.
Copper skink (Oligosoma aeneum): Most commonly encountered skink on Aotea but not as common as it used to be. Often brought inside by cats.
Egg laying skink/Suter’s skink (Oligosoma suteri) At Risk: Very rare to absent on the mainland. Very rare on Aotea. New Zealand’s only egg-laying lizard. Does not survive well in the presence of rats.
Raukawa/common gecko (Woodworthia maculata): Known from coastal areas among rocks and under debris, not as common as it was.
Town’s skink (Oligosoma townsi) At Risk: found only on Aotea, Hauturu, Mokohinau/Pokohinau, Hen and Chickens Islands. Very rare on Aotea, confined to two small catchments. Named after prominent New Zealand herpetologist David Towns who lived some of his early years at Kawa.
Pacific gecko (Dactylocnemis pacificus) At Risk – Relict: Widespread throughout the island, although no longer common.
Shore skink (Oligosoma smithi) At Risk: Still found in limited localised areas on the mainland. Limited to small coastal areas.
Striped skink (Oligosoma striatum) At Risk-Declining: Very few sightings on Aotea and extremely rare on the mainland. Likes mature forest with lots of epiphytes. A very good climber, closest relative is the chevron skink. Identified by obvious pale stripes down the back.
New Zealand’s largest gecko and one of the largest geckos in the world – Duvaucel’s gecko (Hoplodactylus duvaucelii) At Risk – Relict: Very rare on Aotea, this species was not seen for around 40 years until recently found near Windy Hill Sanctuary, Tryphena. Confined to predator-free islands or mainland sanctuaries, Duvaucel’s gecko does not survive with rats.
Environmental News Issue 38 Spring & Summer 2017