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 94mm, with the tail being equal to or slightly longer than the body length

Weight: up to 13.9 grams

Description

The intricately patterned ornate skink is the most widespread reptile in the North Island, occurring from Manawatāwhi / the Three Kings Islands through to Wellington. Although they are widely distributed, ornate skinks are fairly large, and aggressive leading to a higher susceptibility to predation from mammals when compared to some of our other small skinks (e.g., copper skinks), and as such are much more sparse.

In general, ornate skinks are robust with a deep set head and short, blunt snout. The dorsal (upper) surfaces are 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, but as with most of Aotearoa's small endemic skinks, their life expectancy is likely around 10-20 years in the wild.

Distribution

Ornate skinks are the most widespread skink species in the North Island, occurring from Manawatāwhi / the Three Kings Islands at the northern tip of the Aupōuri Peninsula through to Wellington. Although they are widespread, they are generally sparse, with robust populations typically being restricted to islands or areas with good pest control.

Ecology and habitat

A secretive species which rarely emerges from cover. Ornate skinks are cathemeral in nature (active both day and night when conditions are suitable), but are fairly cryptic, remaining at the edge of cover, and hunting amongst dense undergrowth, or deep substrate.

Ornate skinks inhabit forested areas, shrubland and heavily vegetated coastlines; they are often found amongst leaf litter, in dense low foliage, thick rank grass and under rocks or logs, and are known to occupy small burrows (which may be excavated by them, large invertebrates, or other skinks). 

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 reach maturity between 15-16 months and females between 19-20 months.

Diet

The ornate skink is primarily insectivorous, feeding on small arachnids, beetles, and other invertebrates, but is also known to take advantage of the fruit and nectar of certain native plants when they are in season.

Disease

The diseases and parasites of Aotearoa's reptile fauna have been left largely undocumented, and as such, it is hard to give a clear determination of the full spectrum of these for many species.

The ornate skink, as with many of our other Oligosoma species, is likely to be a host for at least one species of endoparasitic nematodes in the Skrjabinodon genus (Skrjabinodon poicilandri), as well as at least one strain of Salmonella. Similarly, as with most ex-Cyclodina skinks they are unlikely to harbour large numbers of ectoparasitic mites in the wild, although they are a recorded host for one species in the Ophionyssus genus.

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

At one time it was thought that the ornate skinks on Manawatāwhi / the Three Kings Island (often referred to as the ‘Manawha’ skink) were a distinct species. However, genetic research has since shown that the population was not genetically divergent from other Oligosoma ornatum populations in Northland.

Jewell (2022) suggested that populations of ornate skink on Northland's outlying islands (Manawatāwhi / the Three Kings Island, etc.) are a distinct subspecies, and gave them the scientific name Oligosoma ornatum longirostrum​​​​​​ in reference to their elongated snout.

The ornate skink, along with its sister taxa (the Aorangi skink) sit within clade 4 (the teardrop skink complex) of the Oligosoma genus, being sister to the rest of the ornate skink complex (e.g. marbledWhitaker's, Hauraki skink etc.). The Falla's skinkrobust skink and Mcgregor's skink are also members of this clade but diverged much earlier.

References

Baling, M., & Mitchell, C. (2021). Prevalence of Salmonella spp. in translocated wild reptiles and effect of duration of quarantine on their body condition. New Zealand Veterinary Journal69(3), 174-179.

Buckley, T. R., & Leschen, R. A. (2013). Comparative phylogenetic analysis reveals long-term isolation of lineages on the Three Kings Islands, New Zealand. Biological Journal of the Linnean Society108(2), 361-377.

Chapple, D. G., Daugherty, C. H., & Ritchie, P. A. (2008). Comparative phylogeography reveals pre-decline population structure of New Zealand Cyclodina (Reptilia: Scincidae) species. Biological Journal of the Linnean Society95(2), 388-408.

Chapple, D. G., Ritchie, P. A., & Daugherty, C. H. (2009). Origin, diversification, and systematics of the New Zealand skink fauna (Reptilia: Scincidae). Molecular phylogenetics and evolution52(2), 470-487.

Cree, A. (1994). Low annual reproductive output in female reptiles from New Zealand. New Zealand journal of zoology21(4), 351-372.

de Lange, P. J., Cameron, E. K., & Taylor, G. A. (1995). Flora and fauna of Tatapihi (Groper) Island, Mokohinau Islands. Tane35, 69-94.

Forester, L. J., & Anderson, P. J. (1995). Vascular plants, vegetation and wildlife of Matapia Island, Far North New Zealand. Tane34, 39-50.

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

Gillies, C., & Clout, M. (2003). The prey of domestic cats (Felis catus) in two suburbs of Auckland City, New Zealand. Journal of Zoology259(3), 309-315.

Gollin, J. F., Gorman, N., & Armstrong, D. P. (2021). Twenty years on. New Zealand Journal of Ecology45(1), 1-9.

Hardy, G. S. (1977). The New Zealand Scincidae (Reptilia: Lacertilia); a taxonomic and zoogeographic study. New Zealand journal of zoology4(3), 221-325.

Hitchmough, R. A. (1977). The lizards of the Moturoa Island Group. Tane23, 37-46.

Hitchmough, R. A. (1979). Lizards observed during a visit to the Cavalli Islands, December 1978 to January 1979. Tane25, 119-124.

Hitchmough, R., Barr, B., Knox, C., Lettink, M., Monks, J. M., Patterson, G. B., Reardon, J. T., van Winkel, D., Rolfe, J., & Michel, P. (2021). Conservation status of New Zealand reptiles, 2021New Zealand threat classification series 35. Wellington: New Zealand Department of Conversation.

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.

Hitchmough, R. A., & Patterson, G. B. (2010). Case 3510 Cyclodina aenea Girard, 1857 (currently Oligosoma aeneum; Reptilia, Squamata, scincidae): proposed conservation of the specific name and suppression of the senior subjective synonym Tiliqua ornata Gray, 1843 (currently Oligosoma ornatum Gray, 1843). The Bulletin of Zoological Nomenclature67(4), 307-313.

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

Jewell, T. (2022). A new islandic subspecies of Oligosoma ornatum (Gray) in the Far North. Jewell Publications, Occasional Publication #2022A.

McCallum, J. (1981). Reptiles of the North Cape region, New Zealand. Tane, 27, 152-157.

McCallum, J., & Harker, F. R. (1982). Reptiles of Little Barrier Island. Tane28, 21-27.

McCallum, J., & Hitchmough, R. A. (1982). Lizards of Rakitu (Arid) Island. Tane28, 135-136.

Melzer, S., Hitchmough, R., van Winkel, D., Wedding, C., Chapman, S., & Rixon, M. (2022). Conservation Status of Reptile Species in Tāmaki Makaurau/Auckland. Auckland Council technical report TR2022/3.

Newman, D. G., & Towns, D. R. (1985). A survey of the herpetofauna of the northern and southern blocks, Great Barrier Island, New Zealand. Journal of the Royal Society of New Zealand15(3), 279-287.

Parrish, G. R., & Anderson, P. J. (1999). Lizard transfers from Matapia Island to Motuopao Island, Northland and observations on other fauna. Tane37, 1-14.

Parrish, G. R., & Gill, B. J. (2003). Natural history of the lizards of the Three Kings Islands, New Zealand. New Zealand Journal of Zoology30(3), 205-220.

Porter, R. (1987). An ecological comparison of two Cyclodina skinks (Reptilia: Lacertilia) in Auckland, New Zealand. New Zealand journal of zoology14(4), 493-507.

Towns, D. R. (1972). The reptiles of Red Mercury Island. Tane18, 95-105.

Towns, D. R. (1999). Cyclodina spp. skink recovery plan 1999–2004: Threatened species recovery plan 27. Wellington: Department of Conservation.

Towns, D. R., & Hayward, B. W. (1973). Reptiles of the Aldermen Islands. Tane19, 93-102.

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

Whitaker, A. H. (1973). Lizard populations on islands with and without Polynesian rats, Rattus exulans (Peale). Proceedings (New Zealand Ecological Society)20, 121–130.