Oligosoma homalonotum

Herpetofaunal category
Authority
Boulenger, 1906
Common names
Chevron skink
Niho taniwha
Oligosoma homalonotum
Image attribution

Also known as ‘Niho Taniwha’, which translates to ‘teeth of the taniwha’ in Maori (a reference to the distinctive chevron markings on the back). The species were first described in 1906, then due to mislabelling of specimens they were 'lost’ for 70 years before being rediscovered in the late 1970's on Great Barrier Island, then in 1991 on Little Barrier Island.

Description

A large skink which reach sizes of up to 143mm SVL (snout-vent-length), or over 30cm from snout to tail. NZ's 'longest' skink, and lizard (mainly by virtue of its tail which can be almost 1.5 x SVL). Dorsal (upper) surface and flanks grey to light reddish brown with a distinct chevron pattern present along tail and back (apexes point towards head). Flanks have small pale blotches. Ventral (lower) surface pale with scattered spots, spots are most concentrated on throat. Distinctive pattern of black and white stripes along the lips, including a pale black edged ‘teardrop’ shape below they eye (this pattern is distinct and can be used to distinguish individuals).

Life expectancy

Little is known about the longevity of the chevron skin, however, a wild born male was held in captivity for approximately 15 years (1985-2000). This individual was identified as an adult when brought into captivity, thus it is estimated that longevity of the chevron skink is at least 20 years, most likely longer (K. Neilson, personal communication).

Distribution

Great and Little Barrier Island in the Hauraki Gulf. They are believed to be pseudo-endemic to these two sites as historical accounts and a single specimen at Auckland Museum indicate they previously occurred on the mainland north of Auckland.

Ecology and habitat

Chevron skink are prone to dehydration, inhabiting stream margins in native forest. The species are excellent climbers and will climb trees when streams and creeks are flooded. Chevron skin have prehensile tails and often hide in tree ferns where their chevron pattern provides excellent camouflage amongst the dead fronds. Chevron skink are able to hold their breath and will retreat underwater if threatened by predators. A diurnal cryptic species, will sometimes sunbathe.

Social structure

Largely unknown, will grunt or squeak if disturbed. 

Breeding biology

Females give birth to litters of up to 8 live young in mid to late summer. It is not known if chevron skink breed annually or biennially.

Diet

Invertebrates including spiders and snails.

Disease

Largely unknown.

Conservation

Listed as ‘nationally vulnerable’ under DOC classification list. A research project was carried out between 1997 and 2002 investigating habitat use and detection methods. DOC have a recovery programme in place for the Oligosoma skink group.

References

  • Baling, M. (2003). The microhabitat use, behaviour, and population genetic structure of the chevron skink (Oligosoma homalonoum). Unpublished masters dissertation, Auckland University, Auckland, New Zealand.
  • Barr, Ben (2005). Chevron Skinks the shy locals of Great Barrier Island. Great Barrier Island Charitable Trust.
  • Barr, B.P. (2009). Spatial ecology, habitat use, and the impacts of rats on chevron skinks (Oligosoma homalonotum) on Great Barrier Island. Unpublished masters thesis, Massey University, Auckland, New Zealand.
  • Gill, B.J., & Whitaker, A.H. (2007). New Zealand frogs and reptiles. Auckland: David Bateman Ltd.
  • 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.
  • Neilson, Keri; Curran, James M.; Towns, David R.; Jamieson, Halema (2006). Habitat use by chevron skinks (Oligosoma homalonotum) (Sauria: Scincidae) on Great Barrier Island, New Zealand. New Zealand Journal of Ecology, 30, 3.
  • Towns, David R., Neilson, Keri A., and Whitaker, A.H. (Tony). (2002). North Island Oligosoma spp. skink recovery plan 2002–2012: Threatened species recovery plan 48. Wellington: Department of Conservation Te Papa Atawhai.