Oligosoma macgregori

McGregor's skink

Oligosoma macgregori
(Robb, 1975)

McGregor's skinks. <a href="https://www.instagram.com/nickharker.nz/">© Nick Harker</a>
Image attribution
McGregor's skinks. © Nick Harker
Herpetofaunal category
NZ Skinks
Species complex
Conservation Status
At Risk - Recovering
Previous scientific names
Cyclodina macgregori
Common names
McGregor's skink

Length: SVL up to 115mm, with the tail being equal to or longer than the body length

Weight: up to 48 grams.

Description

McGregor's skinks are a distinctively patterned, large and robust species. They are well-known for their temperament, and will often bite fiercely when handled. 

Dorsal (upper) surfaces are light to dark brown, either uniform or with long streaks (either paler or darker than the base colour). Flanks grey brown with irregular black markings and numerous pale streaks or blotches (often with a dark edge), which merge into a dark area above the forelimbs. Belly yellow to pink, either uniform or with dark flecks; throat cream coloured, sometimes with a spattering of dark flecks. A pale, black outlined tear drop is seen under each eye.

Life expectancy

Ages of over ten years recorded for wild animals. Captive animals have been reported to live 55+ years (D. Keall, personal communication, May 22, 2021).

Distribution

Originally found throughout the North Island, McGregor’s skinks are now restricted to a fraction of their former range. They now only occur on a few pest-free islands scattered between Northland and Wellington; four remnant populations exist (Mana Island, Sail Rock, Bream and Cavalli Islands), and two translocated populations (Lady Alice and Whatupuke Islands). 

Ecology and habitat

McGregor's skinks are a large crepuscular or nocturnal species. They are particularly susceptible to evaporative water loss through their skin, so utilise humid and thermally stable microhabitats. 

They occupy a range of coastal habitats including open rocky platforms among dense vegetation such as flax (Phormium spp.), and New Zealand iceplant (Disphyma australe). They also inhabit coastal forest and scrub where they take refuge among thick leaf litter, under rocks and logs, or in seabird burrows during the day.

Social structure

McGregor's skinks are solitary and aggressively territorial. They have been recorded attacking and killing other lizards (including their own species) when caught in pitfall traps.

Breeding biology

McGregor’s skink are ovoviviparous, giving birth to litters of up to seven in late summer to early autumn (D. Keall, personal communication, May 22, 2021).

Diet

McGregor’s skink are primarily insectivorous, but also prey on smaller species of lizards such as moko skinks (Oligosoma moco), and possibly consume carrion or regurgitated fish where they occur near seabird colonies. As with other native skinks, they likely forage for fruit and berries from native plants.

Disease

Largely unknown.

Conservation strategy

McGregor’s skinks have been heavily impacted by the introduction of mammalian predators and are now one of our rarest species. They currently occupy less that 1% of their former range, and only occur on pest-free islands as they cannot coexist with introduced predatory mammals such as rats and mice.

McGregor’s skink have been translocated from Sail Rock to establish two new populations on pest-free islands: Lady Alice and Whatupuke Island in the Marotere / Hen and Chicken group.

DOC have a recovery programme in place for the Oligosoma skinks, and list McGregor's skinks as ‘recovering’ due to expansion of translocated populations, and their recovery on Mana Island following the eradication of mice.

Interesting notes

Named in honour of Professor William Roy McGregor former head of the Zoology Department at the University of Auckland.

Genetic studies have shown that there is little divergence in populations of McGregor's skinks on Sail Rock (north of Auckland) and Mana Island (near Wellington), suggesting that there was substantial gene flow between these populations prior to the species decline. 

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 Publishing Ltd.

Newman, D.G. (1994) Effects of a mouse, Mus musculus, eradication programme and habitat change on lizard populations of Mana Island, New Zealand, with special reference to McGregor’s skink, Cyclodina macgregori. New Zealand Journal of Zoology, 21, 443-456.

Towns, D.R. (1999) Cyclodina Spp. Skink Recovery Plan 1999-2004. Threatened Species Recovery Plan 27. Department of Conservation, Wellington, New Zealand.

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