Oligosoma whitakeri

Whitaker's skink

Oligosoma whitakeri
(Hardy, 1977)

Whitaker's skink (Ngā Manu Nature Reserve). <a href="https://www.instagram.com/nickharker.nz/">© Nick Harker</a>
Image attribution
Whitaker's skink (Ngā Manu Nature Reserve). © Nick Harker
Herpetofaunal category
NZ Skinks
Species complex
Conservation Status
Threatened - Nationally Endangered
Previous scientific names
Cyclodina whitakeri
Common names
Whitaker's skink

Length: SVL up to 101mm, with the tail being equal to or slightly longer than the body length

Weight: up to 20 grams

Named in honour of the renowned New Zealand herpetologist Anthony (Tony) Whitaker.

Description

A large, and highly secretive skink with intricate cream/yellow and black blotching on it's flanks. Whitaker's skinks were formerly widespread in the North Island, but are now one of our rarest lizards.

Males weigh up to 20g, and breeding females 25-26g (D. Keall, personal communication, October 18, 2016). Dorsal (upper) surface colours range from yellow/brown to dark brown; back covered with light to dark flecks which may be indistinct or very prominent. Flanks cream to yellow or brown, usually heavily mottled with black, particularly on the sides of the neck. This typical flank pattern can also be reversed with a black background colour with pale mottling. Ventral (lower) surfaces: yellow to orange belly, usually unmarked or faintly marked; throat pale grey. Sides and top of tail sometimes have an orange hue. The head is deep set with a short, blunt snout. A pale, black edged tear drop is present beneath each eye. Pattern may fade considerably with age (see image gallery).

Whitaker’s skinks are similar in appearance to marbled skinks. However, marbled skinks usually have a heavily marked belly. Juvenile Whitaker’s skinks can appear similar to ornate skinks but have more ventral scale rows.

Life expectancy

Individuals have been known to live over 46 years in captivity (D. Keall, personal communication, October 18, 2016).

Distribution

Prior to the arrival of humans and the pests they brought with them, Whitaker’s skinks were widespread in the North Island. Subfossil remains of this species have been found on Motutapu Island near Auckland, in the Waikato region, and to as far south as Wellington (Worthy, 1987).

At the time of their discovery they were only known from three locations: Middle Island (Mercury group) and Castle Island off the Coromandel peninsula; and a small population at Pukerua Bay on the mainland north of Wellington. The small population at Pukerua Bay is now presumed extinct in the wild and a small population is held in captivity as part of a breeding programme. 

The species has been translocated from Middle Island to two further islands in the Mercury group: Korapuki Island in 1988, and Red Mercury Island in 1994.

Ecology and habitat

Whitaker’s skinks inhabit leaf litter and seabird burrows in coastal forests and scrub. At Pukerua Bay the species was occupying a coastal boulder bank interspersed with patchy Muehlebeckia sp. vineland.

A crepuscular and nocturnal species which are active at dawn and for several hours after dusk. Whitaker's skinks are active over a very narrow climatic range, with capture rates at Pukerua Bay indicating that the temperature preference for activity is 15-20°C. Gravid females will sun bask.

Social structure

Largely unknown; observations of captive animals indicate that the species prefer to live solitarily (D. Keall, personal communication, October 18, 2016).

Breeding biology

Whitaker’s skinks are ovoviviparous, giving birth to litters of up to five young in April.

Diet

Whitaker’s skinks are carnivourous, feeding on prey such as: moths, beetles, spiders, grubs, hoppers, and worms. They are known to forage within seabird burrow complexes and boulder banks.  

Disease

Largely unknown.

Conservation

DOC classify Whitaker’s skinks as ‘nationally endangered’. DOC have a recovery programme in place for the Oligosoma skink group, and a specific recover plan for Whitaker’s skink.

Whitaker's skinks were translocated from Middle Island to two additional pest free islands in the Mercury group (Korapuki and Red Mercury Island), to help safeguard the species.

A project is being undertaken by DOC and Friends of Mana Island to capture, breed and relocate a population of vulnerable Whitaker’s skinks from Pukerua Bay to predator free Mana Island. There is some uncertainty and concern about how Whitaker’s skinks might interact with the larger and more aggressive McGregor’s skink (Oligosoma macgregori) which are already present on the Island (subfossils indicate the two species have been sympatric in the past but no longer coexist at the same sites due to relictual distributions.

Interesting notes

Whitaker's skinks were named in honour of the renowned New Zealand herpetologist Anthony (Tony) Whitaker.

Whitaker's skinks were once widespread in the North Island, but only three small populations survived following the introduction of mammalian predators, and they are now one of our rarest lizards.

Genetic studies have shown that there is little genetic divergence between populations of Whitaker's skinks on islands in the Coromandel area, and those which occured on the mainland near Wellington (Chapple et al., 2008). This suggests that there was substantial gene flow across their range prior to their decline due to mammalian predators.

References

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 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 Ltd.

Towns, D. (1992). Recovery plan for Whitaker’s skink and robust skink: Threatened species recovery plan series no. 3. 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.

Worthy, T. H. (1987). Osteological observations on the larger species of the skink Cyclodina and the subfossil occurrence of these and the gecko Hoplodactylus duvaucelii in the North Island, New Zealand. New Zealand Journal of Zoology, 14:2, 219-229, DOI: 10.1080/03014223.1987.10422992