Otago skink (Oligosoma otagense)
|Size||Length: 25 – 30 cm (2)|
The Otago skink is classified as Endangered (EN) on the IUCN Red List (1).
One of New Zealand’s rarest lizards, and also amongst the largest (2), the Otago skink (Oligosoma otagense) is a long and slender reptile. Its scaly body is yellow or greenish on the upperparts, pale grey on the underside, and mottled all over with darker patches. Juvenile Otago skinks differ from the adults in their colouration, with black blotches adorning a bright yellow body (3). The forelimbs are somewhat shorter than the hindlimbs and the snout is fairly sharp (3).
The Otago skink is known only from the region of New Zealand after which it is named, Otago, on the South Island (2). Once covering a much wider area, the Otago skink is now known from just two areas within Otago that together cover just eight percent of its former range (4).
An inhabitant of rocky outcrops, the Otago skink prefers sheltered places, near rivers or streams, between 200 and 950 metres above sea level. It is more commonly found at rocky outcrops that are surrounded by tussock grassland or native scrub rather than agricultural land (2).
The Otago skink is an omnivorous reptile, which feeds on a wide variety of invertebrates, vegetation and, when in season, soft fruits (4). Occasionally it also consumes small skinks and flower petals (4). Although the Otago skink forages for most of its food on the rocks, particularly areas which are encrusted with lichen that attract a richer abundance of invertebrate prey (2), it must occasionally leave the rocks to find some of its food, such as fleshy fruits and more invertebrates (3), in the surrounding plant life (2).
Female Otago skinks give birth to between two and four young at a time. Otago skinks reach maturity at the age of three or four (2) and are known to live for up to 16 years in the wild (4).
Like most reptiles, the Otago skink depends on its environment to regulate its body temperature. Thus they are often seen lying out on the rock, basking in the sun, and retreat to the cool of crevices when the day grows too hot (3). Lichen encrusted rock surfaces not only provide a source of invertebrate prey, but also offer the rare Otago skink better camouflage against predators (2). Deep rock crevices also provide shelter from predators (2), and should the Otago skink be attacked, like other skinks it can readily discard its tail, giving it a better chance of escaping its predator (5).
Over the last 25 years, the Otago skink has declined in both numbers and range, and as these worrying declines continue (2), this endemic reptile is now considered to be Endangered (1). Although the exact causes behind these declines have not been clearly identified, habitat loss and the effects of introduced species are believed to be the main factors responsible (2) (4). The conversion of tussock grassland and native scrub to agricultural land, as well as grazing and burning, reduce the amount of native fruits and invertebrates on which the skink feeds (4). Similarly, mining, quarrying, forestry and invasion by weeds can reduce the amount of suitable habitat for the Otago skink (4). Mammalian predators are also a significant threat to the survival of Otago skink populations, largely due to their enormous numbers; cats, ferrets, stoats, weasels, ship rats, Norway rats, hedgehogs and mice are all potential predators of the Otago skink (4).
Despite its worrying situation, the Otago skink is thankfully the subject of a number of conservation measures. It is fully protected by law, meaning that it is an offence to capture or disturb this species (2), and most of the skink populations in the eastern part of its range exist in land protected and managed by the New Zealand Department of Conservation (4). A recovery plan for this species was first published in 1995, and a second plan was published in 2006 (4). After the first one, measures were implemented to control cats and ferrets in certain areas, but the skink populations failed to recover. Thus a new management scheme was imposed to see if skink populations recover if all mammalian predators are eradicated or removed (4). Certain populations will be surrounded by a mammal-proof fence, and all mammals eradicated within the area, while other will have no fence and instead traps will be used to control predators. The effects of these treatments are not anticipated to be detected until 2009, and then depending on the outcome, the most successful measure can then be implemented in other populations (4).
If neither measure is successful in preventing further declines in skink populations, then more importance will be placed on the captive breeding of Otago skinks. As of 2006, 86 Otago skinks were held in captivity, where this species has been successfully bred, providing a safeguard against this species’ extinction should the worst happen in the wild (4). In combination with these measures, the second recovery plan outlines the importance of continued monitoring of this species, in addition to increasing awareness of this species’ perilous situation with the general public, and raising the profile of skink conservation (4).
Find out more about the conservation of the Otago skink and how you can get involved:
New Zealand Department of Conservation:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Invertebrates: animals with no backbone.
- Omnivorous: feeding on both plants and animals.
IUCN Red List (February, 2011)
- Whitaker, A.H. and Loh, G. (1995) Otago Skink and Grand Skink Recovery Plan. Threatened Species Recovery Plan No. 14. Threatened Species Unit, Department of Conservation, Wellington, New Zealand.
- Patterson, G.B. (1997) South Island skinks of the genus Oligosoma: description of O. longipes n. sp. with redescription of O. otagense (McCann) and O. waimatense (McCann). Journal of the Royal Society of New Zealand, 27(4): 439 - 450.
- Norbury, G., Reardon, J. and McKinlay, B. (2006) Grand and Otago Skink Recovery Plan 2006-2016. Draft. Threatened Species Unit, Department of Conservation, Wellington, New Zealand.
- Burnie, D. (2001) Animal. Dorling Kindersley, London.