Oligosoma roimata

Aorangi skink

Oligosoma roimata
(Patterson et al., 2013)

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Image attribution
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Herpetofaunal category
NZ Skinks
Species complex
Conservation Status
At Risk - Naturally Uncommon
Previous scientific names
Cyclodina ornata
Common names
Aorangi skink,
Poor Knights skink.

Length: SVL up to 65mm, with the tail being equal to or shorter than the body length

Weight: unknown

Description

Aorangi skinks are an island-endemic relative of the ornate skink (Oligosoma ornatum), and descended from common ancestors of the two species which became isolated on the Poor Knights Islands. 

Similar in appearance to ornate skinks but with a more pointed snout, and pale-coloured (versus usually yellow or salmon-coloured) belly. Head often has black speckling on top, and a prominent tear-drop marking below the eye. Dorsal surfaces are brown or grey-brown, with or without lighter and darker speckling. Dorsolateral stripes are pale-brown or copper, bordered below by a black marking / stripe which extends slightly onto the flanks and may have a jagged edge. Lateral surfaces are a lighter grey-brown and either uniform or with lighter spots which are often outlined in dark-grey or black. Ventral surfaces are white or cream and lightly speckled. Can be distinguished from the syntopic Hardy's skink (Oligosoma hardyi) by the presence of a pale dark-edged tear-drop marking below the eye (versus denticulate patterning along the mouth on Hardy's skinks).

Life expectancy

Unknown.

Distribution

Endemic to the Poor Knights Islands off Northland. Found only on the two largest islands in the Poor Knights group (Aorangi and Tawhiti Rahi).

Ecology and habitat

Little is known about the ecology of Aorangi skinks. They are either cathemeral (active day or night when conditions are favourable) or crepuscular. Aorangi skinks are a cryptic species, but have been known to bask near cover / refuge sites.

They occupy areas of coastal forest either on the edge or forest interior. When not actively foraging they take refuge in dense low vegetation, or under rocks and logs. They can be found near colonies of burrowing seabirds and may take refuge in the burrows.

Social structure

Solitary.

Breeding biology

Unknown, but likely similar to the closely related ornate skink (Oligosoma ornatum).

Diet

Aorangi skinks are known to feed on small invertebrates (insects, crustaceans etc.)

Disease

Unknown.

Conservation strategy

The Poor Knights islands have been pest-free since 1936 when feral pigs were eradicated. Because Aorangi skinks only occur on pest-free islands, and occupy the entire extent of their historical range, no specific conservation action is required other than maintaining biosecurity to keep the islands pest-free. 

Interesting notes

The Poor Knights Islands are an area of high endemism. Many lizards on the Poor Knights islands are closely related to species which occur on the mainland, and are descended from common ancestors which became isolated when the islands separated from the North Island mainland around 2 million years ago. The Aorangi skink diverged from ornate skink (Oligosoma ornatum) common ancestors, other examples include Hardy's skink (O. hardyi) - which diverged from copper skink (O. aeneum) common ancestors, and the Poor Knights gecko (Dactylocnemis "Poor Knights") which diverged from Pacific gecko (D. pacificus) common ancestors.

References

Hayward, B.W. (1991). Geology and geomorphology of the Poor Knights Islands, northern New Zealand. Tane, 33, 23-27.

Hitchmough, R.A., Barr, B., Lettink, M., Monks, J., Reardon, J., Tocher, M., van Winkel, D., Rolfe, J. (2016). Conservation status of New Zealand reptiles, 2015; New Zealand threat classification series 17. Wellington: New Zealand Department of Conservation.

Jewell, T. (2011). A photographic guide to reptiles and amphibians of New Zealand. Auckland: New Holland Publishing.

van Winkel, D., Baling, M. & Hitchmough, R. (2018). Reptiles and Amphibians of New Zealand: A field guide. Auckland: Auckland University Press, 376 pp.