Oligosoma ornatum

Ornate skink

Oligosoma ornatum
(Gray, 1843)

Ornate skink (Auckland). © Nick Harker
Image attribution
Ornate skink (Auckland). © Nick Harker
Herpetofaunal category
NZ Skinks
Species complex
Conservation Status
At Risk - Declining
Previous scientific names
Cyclodina ornata ,
Sphenomorphus pseudornatus
Common names
Ornate skink,
Teardrop skink,
Rata skink.

Length: SVL up to 84mm, with the tail being equal to or slightly longer than the body length

Weight: up to 11.5 grams

Description

An intricately patterned species which is widespread in the North Island, but generally sparse in areas without predator control.

Ornate skinks are robust with a deep set head and short, blunt snout. Dorsal (upper) surface light tan through to a very dark brown/almost black. Individuals usually have a dark 'wavy' edged stripe extending from the nostril to above the eye, and along the edge of the dorsum/flanks, often breaking up midway between the fore and hind limbs. Large pale blotches are seen along the top and sides of the tail, which often extend onto the back. In some individuals the tail may be flushed with red/orange. Ventral (lower) surface yellowish, either unspotted, partially or wholly spotted with black; some individuals have vivid reddish orange colouration. Head sports a ‘tear-drop’ below each eye (white or yellowish edged with black). Tail is thick at the base and tapers abruptly. Females are generally larger than males, with males rarely exceeding 70mm SVL, whereas females will often exceed 75mm SVL. Individuals have: between 15-23 lamallae on each toe; 28-34 mid body scales; 60-79 ventral scale rows.

Ornate skinks may be confused with Whitaker’s skink (Oligosoma whitakeri), but can be differentiated by having less ventral scale rows (60-79 vs 84-99). Similar to Hauraki skinks (Oligosoma oliveri) and Coromandel skinks (Oligosoma pachysomaticum) but can be differentiated by have less extensive black markings on the neck area.

Often confused with the more-common copper skink (Oligosoma aeneum), but can be distinguished by the presence of a tear-drop pattern under the eye (versus denticulate patterning in copper skinks), and proportionately larger ear-hole.

Life expectancy

Largely unknown.

Distribution

Widespread throughout the North Island, however populations are sparse as they are generally only found in large numbers in protected sites or on islands.

Ecology and habitat

Ornate skinks are crepuscular (active at dawn and dusk); a cryptic species which seldom emerge from cover, though they can be observed basking near reatreat sites during the day.

Ornate skinks inhabit forested areas, shrubland and heavily vegetated coastlines; found amongst leaf litter, in dense low foliage, thick rank grass and under rocks or logs.

Social structure

Ornate skinks are solitary with adults being quite aggressive. Adults will not co-habit, however, it appears that they will tolerate their own young with large females being observed occupying the same refuge as 2-3 young (N. Harker, personal communication, December 1, 2016).

Breeding biology

Ornate skinks are ovoviviparous, giving birth to live young in January/February. It appears they may be able to have up to 8 offspring in a single clutch; with 2-4 large ova in each ovary. The average size for neonates is 25.5mm SVL. Males mature at between 15-16 months and females at between 19-20 months.

Diet

Insectivorous and frugivorous.

Disease

Ophionyssus species of mite have been found on ornate skink.

Conservation strategy

DOC classify ornate skink as ‘At risk - Declining’ with a total area of occupancy >10,000 ha (100km2), but a predicted decline of 10-70%. The species were included in DOC’s Cyclodina spp. skink recovery plan 1999 - 2004.  

Interesting notes

It was suggested that the ‘Manawha’ skink of the Three Kings Island was a distinct species. Genetic research have since shown that the population was not genetically divergent from the Oligosoma ornatum populations of Northland.

References

Chappel, D.G., Daugherty, C.H., Ritchie, P.A. (2008). Comparative phylogeography reveals pre-decline population structure of New Zealand Cyclodina (Reptilia: Scinidae) species. Biological Journal of the Linnean Society, 95, 388-408.

Gill, B.J., & Whitaker, A.H. (2007). New Zealand frogs and reptiles. Auckland: David Bateman Limited.

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 Publishers.

Towns, D.R. (1999). Cyclodina spp. Skink recover plan, 1999-2004. Wellington: Department of Conservation.

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