Oligosoma aff. polychroma Clade 3

South Marlborough grass skink

Oligosoma aff. polychroma Clade 3

South Marlborough grass skink (Kaikōura). <a href="https://www.instagram.com/samanimalman/">© Samuel Purdie</a>
Image attribution
South Marlborough grass skink (Kaikōura). © Samuel Purdie
Herpetofaunal category
NZ Skinks
Species complex
Conservation Status
At Risk - Declining
Previous scientific names
Oligosoma polychroma,
Oligosoma nigriplantare polychroma,.
Common names
South Marlborough grass skink,
Common skink.

Length: SVL up to 80mm, with the tail being equal to or slightly longer than the body length

Weight: unknown

Description

Formerly regarded as the 'common skink' (which has now been split into five separate species), south Marlborough grass skinks are one of the lesser-known and rarely encountered members of the grass skink species complex.

Similar in appearance to other members of the grass skink complex and very difficult to distinguish. Head has a short, blunt snout. Pattern can be highly variable. The dorsal surfaces are often various shades of brown with cream or pale-brown dorsolateral stripes which may be smooth-edged or serrated, a mid dorsal stripe (when present) usually extends down the tail. Flanks have a broad dark brown lateral stripe, often edged with black and bordered below by a cream-coloured stripe which may be smooth or crenulated. A pale stripe runs down the anterior surface of the forelimb. The ventral surface is variously coloured shades of grey, brown, or yellow, without speckling.

Life expectancy

Unknown.

Distribution

Occurs in the South Island, with a relatively small range from inland southern Marlborough, southwards through the seaward and inland Kaikoura ranges, to as far south as northern Canterbury.

Ecology and habitat

South Marlborough grass skinks are diurnal, bold and strongly heliothermic. Little else is known of their ecology.

In common with other grass skinks the species occupies a wide range of habitat types preferring open areas including rock piles, grassland, open shrubland, screes, forest margins and tussock. Often takes refuge in dense vegetation or under rocks, logs and other debris when not active.

Social structure

Unknown, though likely similar to other members of the grass skink complex e.g. Oligosoma polychroma.

Breeding biology

Little is known about the breeding biology of south Marlborough grass skinks. However it is likely that they are similar to other members of the grass skink complex - reaching maturity in around two years, with mature females giving birth annually to litters of up to six juveniles in mid-to-late summer (January- February).

Diet

South Marlborough grass skinks are active hunters and consume a wide range of small invertebrates such as spiders, insects, isopods and molluscs. They also consume the berries / fruit from native plants.

Disease

Unknown.

Conservation strategy

south Marlborough grass skinks are regarded as "At Risk - Declining."

No specific conservation strategy has been developed for south Marlborough grass skinks and they are exposed to predation by introduced mammals (i.e. rats, mice, cats, mustelids) throughout their natural range.

Interesting notes

South Marlborough grass skinks are members of a cryptic species complex which includes the northern grass skink (Oligosoma polychroma), Waiharakeke grass skink (Oligosoma aff. polychroma Clade 2), Canterbury grass skink (Oligosoma aff. polychroma Clade 4), and southern grass skink (Oligosoma aff. polychroma Clade 5). The various species are regionally distributed, similar in both appearance and habit, and were once regarded as a single highly variable species - the 'common skink'. There are currently no known morphological features to distinguish south Marlborough grass skinks from the other species within the complex.

References

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 Evolution, 52(2), 470-487.

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.

Robb, J. (1986). New Zealand Amphibians & Reptiles (Revised). Auckland: Collins, 128 pp.

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