Length: SVL up to 116mm, with the tail being equal to or longer than the body length
Very robust with a deep-set head and snout. Dorsal surface light brown with indistinct lighter and darker patches giving a characteristic slight marbled or mottled effect. Sides of head and neck dark grey to blackish-grey with large irregular white patches, this colouration either continuing along the sides of the body and tail or merging into a lighter grey-brown with darker and lighter blotches and speckles. Belly cream with broad dark blotches; throat white with heavy speckling or streaks. The head sports a ‘tear-drop’ marking under each eye (white with black edging); the remainder of the ‘lips’ often with much finer pale denticulate (‘tooth-like’) markings. Tail is short and thick, tapering abruptly.
Marbled skinks co-exist with four other species of skink, including the much smaller shore skink (Oligosoma smithi; 80 mm SVL), Aorangi skink (Oligosoma roimata; 65 mm SVL), and Hardy’s skink (Oligosoma hardyi; 62 mm SVL). It can also easily be confused with the sympatric egg-laying skink (Oligosoma suteri), which can be almost as large, but lacks the tear-drop marking from beneath the eye, and is more gracile with a distinctly narrow, pointy snout.
Marbled skink are restricted to the Poor Knights Islands off the coast of Northland.
Ecology and habitat
Lives on the floor of coastal forest and scrub, using leaf litter, seabird burrows, and other ground cover to hide. Marbled skinks are nocturnal, with peaks of activity after dusk and before dawn, and it is suspected that they may employ a ‘sit and wait’ strategy for hunting prey between these periods of active movement. Gravid females have occasionally been found basking in dappled sunlight on the forest floor but otherwise the species appears to shun bright light.
Marbled skink are ovoviviparous giving birth to litters of 2-4 young in March/April.
Invertebrates and fruit including berries of Coprosma, Macropiper excelsum (kawakawa), and Solanum nodiflorum (small flowered knightshade).
Ophionyssus mites have been recorded as ectoparasites of marbled skink.
Marbled skinks may be naturally endemic to the Poor Knights Islands, in which case they likely still occur at their full natural distributional extent and abundance. As a large ground-dwelling lizard confined to a small and close-knit collection of islands, however, they are highly vulnerable to rodent invasion or habitat damage such as fire.
Named after the former Director of the Dominion Museum, Dr W.R.B. Oliver. Accordingly, marbled skink is sometimes referred to as Oliver’s skink.
The marbled skink species-complex has proven especially difficult to resolve because genetic traits have often suggested a different evolutionary scenario than what other (morphological, ecological and biogeographical) traits imply, and as a result the taxonomy of the complex has been much debated and somewhat unstable for the past thirty years. The definition of the marbled skink has thus changed from its original concept of a Poor Knights Islands endemic (McCann 1955), to a species widespread among various islands from the Poor Knights south to the Coromandel Peninsula area (Hardy 1977), to one found on the Poor Knights and Coromandel areas but not in between (Chapple et al. 2008), and eventually back to its original Poor Knights Islands only concept (Jewell 2019).
Chapple, D.G., Patterson, G.B., Gleeson, D.M., Daugherty, C.H. & Ritchie, P.A. (2008b) Taxonomic revision of the marbled skink (Cyclodina oliveri, Reptilia: Scincidae) species complex, with a description of a new species. New Zealand Journal of Zoology, 35, 129–146.
McCann, C. (1955) The lizards of New Zealand. Gekkonidae and Scincidae. Dominion Museum Bulletin, 17, 1–127.
Hardy, G.S. (1977) The New Zealand Scincidae (Reptilia: Lacertilia); a taxonomic and Zoogeographic study. New Zealand Journal of Zoology, 4, 221–325.
Jewell, T.R. (2019) New Zealand forest-dwelling skinks of the Oligosoma oliveri (McCann) species-complex (Reptilia: Scincidae): reinstatement of O. pachysomaticum (Robb) and an assessment of historical distribution ranges. Zootaxa 4688(3): 382-398.
van Winkel, D., Baling, M. & Hitchmough, R. (2018). Reptiles and Amphibians of New Zealand: A field guide. Auckland: Auckland University Press, 376 pp.