Robust Skink

The New Zealand skink fauna is incredibly diverse, coming from a monophyletic lineage to many species with varying morphologies. The robust skink is the largest in New Zealand with a maximum recorded snout-vent length of 150mm2, length of up to 33 cm and weight of 105 grams. These skinks are large with short limbs and toes, with a thickset body. Characterising points of these skinks are large body, and mid-dark brown dorsal colouring, often broken up with large cream/pale blotches. Some individuals are seen to have black and white markings above shoulders with ventral areas of the body showing vivid reddish pink colouring. Below each dark eye, a black-edged teardrop shape can be seen. The snouts are round and blunt. Tails are thick and quickly taper off. Given their large shape and clear markings the robust skink is unlikely to be confused with other types of skinks. Robust skinks lack common reptile predator avoidance features such as body armour. Hence the evolution of camouflage patterning features allowing this species to be cryptic and avoid identification as food by predators. Robust skinks can show extreme longevity in adulthood, with recorded ages of 33 and 55 years in captivity.

Members of the North New Zealand herpetofauna have faced range declines due to mammalian predation and colonisation. Following the first wave of mainland reptilian extinctions the robust skink is only found on rodent free islands off the North Island of New Zealand. Subfossils have been recorded from areas such as Motutapu Island (Auckland), Waitomo and Martinborough. The robust skink is strictly nocturnal to maximise benefits and reduce costs of feeding. They are a forest-dwelling species, occupying seabird burrows, rocky areas and deep forest litter. Like other Oligosoma skinks, the robust skink is physiologically restricted to moist microenvironments, as they are susceptible to water loss through their skin. Thus, they prefer areas of high humidity. To avoid water loss and maximise survival chances the skinks, spend the day in thick leaf litter, hide under rocks and find refuge in seabird burrows, such behaviour is both innate and learned.

As seen in other lizard species, the mating behaviour in Oligosoma is rather violent. The male often repeatedly bites the female around the neck and head area causing scarring. This behaviour is common among skink species as a mate selection strategy, to assess the relative quality of the female.

The specific epithet, alani, was given by the describer Joan Robb in honour of her nephew, Alan Robb.