Rainbow Skink Unwanted on Aotea
Could this be lurking in your luggage?
by Halema Jamieson

He may look harmless but this curious little lizard is bad news. Originally from Australia, his relatives first arrived in Auckland in the 1960s. Since then they’ve been breeding up a storm and helping themselves to free rides across the North Island. ‘He’ is a rainbow skink, an unwanted visitor who has recently arrived uninvited on Great Barrier Island.

What is a rainbow skink?
Rainbow skinks (Lampropholis delicata) are small brown or greyish brown lizards with an iridescent metallic (rainbow) sheen when seen in the right light. They are sometimes also known as the “delicate skink” or “plague skink”. At only around 3-4cm from the nose to hind legs (snout to vent length or SVL), or about 8cm including their long thin tail, they are smaller than any of our native skink species. Our native copper skinks (Oligosoma aeneum) can look similar but are generally stockier in appearance and lack the rainbow sheen. The most distinguishing characteristic is the head scale as shown in the photo and diagram opposite. Rainbow skinks have one large diamond shaped scale on the top of the head. Native species have two smaller scales.

Legal Status in New Zealand
The Ministry for Primary Industries, MPI (previously MAF) has classified the rainbow skink as an UNWANTED ORGANISIM under the Biosecurity Act 1993. This means that it is illegal to knowingly move, release, spread, breed or sell them. All of our native lizards (skinks and geckos) are protected under the Wildlife Act 1953 and must not be intentionally captured, injured, killed or kept in captivity without specific permission from the Department of Conservation.

Where do they live?
Rainbow skinks are diurnal and most active on warm sunny days. They live amongst leaf litter and dense low vegetation in mostly open habitats such as grassland, gardens, road clearings and coastal areas. In addition, they are also fond of debris and rubbish (such as corrugated iron, plywood, packing materials etc.) lying about in warm open areas.

Where else are they found?
In their native country of Australia, rainbow skinks are found along the eastern coast from Cairns to Tasmania.
Since their arrival to Auckland, NZ, rainbow skinks have spread to the Waikato, Bay of Plenty (excluding Rotorua), Palmerston North and Whanganui. They have also managed to island-hop to several island in the Hauraki Gulf including Waiheke, Rotoroa, Rangitoto and Motutapu.
Today, they are the most common skink encountered in urban Auckland areas. In addition to New Zealand, they have also made their way to the islands of Hawaii and Lord Howe.
 
Native skink left,

Rainbow skink right.



    Images by G Maslowski.  Head of rainbow skink showing distinguishing diamond shaped headscale.  Diagram: TG Whitaker

 

How did they get here?
Rainbow skinks are expert stowaways and will take any opportunity to hitch a ride. Either as eggs or live lizards they have been found amongst a variety of freight and luggage including building materials, potted plants, mulch, bags, packs, cars and camping equipment. One skink even managed to catch a ride from Auckland to Wellington appearing in a bag of salad bought from a supermarket in Porirua.

Why are they a problem?
Compared to our native lizards, rainbow skinks live fast and die young. All but one of our native species give birth to live young and can live for several years. Some of our gecko species have been recorded reaching up to 40 years in the wild. They take their time and most do not start breeding until they are three or four years old and even then, not every year. By comparison, rainbow skinks have a life span of only around two to three years but they make the most of it. They lay small white leathery eggs (8-10mm long), up to five at a time, in communal nests of up to 100 eggs and can quickly build up to high densities. In Hawaii, they have been termed the ‘Plague skink’ and are now the most common skink found there. By attaining such large numbers over a short time, rainbow skinks are able to occupy and ‘take over’ valuable native skink habitat and out compete them for food.

What is being done?
Rainbow skinks have been found around the Tryphena wharf. This summer a control programme is being implemented by the Auckland Council in an attempt to eliminate them. Several methods will be employed including trapping, tracking and visually searching the area.

Rainbow skinks are easily transported in freight and rubbish. They could very easily make their way to other parts of Great Barrier Island. In addition to the control programme at Tryphena wharf, surveillance has begun at several high-risk sites around the island such as wharves, plant nurseries, building sites, rubbish and recycling stations and the dump. Tracking tunnels containing non-toxic ink pads and artificial cover objects (ACOs) made from small sheets of corrugated Onduline have been placed at these sites to detect the lizards or their eggs. These will be checked regularly along with visual searches over the summer by Auckland Council contractor, Jacqui Wairepo.

What can I do?
Rainbow skinks are clever stowaways and can easily make their way to Great Barrier in building supplies, garden media and camping equipment. To ensure Rainbow skinks are not inadvertently transported to other parts of the island or new skinks accidentally introduced, everyone can help by inspecting goods and material being brought to the island or moved from the Tryphena wharf area. Be careful where you purchase garden supplies such as potting mix, compost and mulch off island. Many large-scale garden centres and building supply depots are heavily infested with rainbow skinks and argentine ants. As a precaution, any plants brought to the island should be dunked in water for at least two minutes so that any rainbow skink eggs or ants float to the surface.

 Keep an eye out for small fast moving skinks and their eggs around your place and amongst your freight. Identification can be tricky so get a photo and contact Jeremy Warden, Auckland Council Biosecurity Officer: jeremy.warden@aucklandcouncil.govt.nz (09) 307 7661

For further information on this pest: http://www.biosecurity. govt.nz/pests/rainbow-skink