A hunt is under way on the Poor Knights Islands to find out why shore skinks on the isolated ecological fortress are jet black, unlike their paler cousins on the mainland.
Massey University PhD student Marleen Baling and two other researchers are spending five days on the Poor Knights Island of Aorangi studying why the local shore skink is a different colour to others, and particularly why such a dense black. It is the first formal scientific study on native reptiles' colour variation.
The shore skink is one two native lizard species restricted to the northern coastline of New Zealand, but nowhere else is the entire local population completely black. Elsewhere the rock and driftwood-dwelling creatures range from mid-brown and shades of grey to almost black, Ms Baling said.
Natural selection could be at the root of variation due to predation or sexual selection, such as mate choice and population pressure.
The Poor Knights Islands, 12 kilometres off the Tutukaka coast, separated from the mainland over two million years ago and many of its species have adapted to the ecology in isolation.
The shore skink grows to 8cm and eats insects and other creatures that fit in its mouth. In turn, it is eaten by birds and, at the Poor Knights, a larger prehistoric native lizard, the tuatara.
Ms Baling's team was dropped off on Monday at one of a few places boats can unload on the islands' rugged coast. The detour was another exciting diversion for Perfect Day Dive Tutukaka passengers who also found themselves party to the release of three tropical turtles.
The two hawksbills and one green turtle were found in northern New Zealand waters, sick and disoriented, and had been treated long term at the Kelly Tarlton Sea Life Aquarium in Auckland.
Only people on official research or conservation projects can land at the Poor Knights Islands nature reserve, which carries one of the highest conservation classifications in New Zealand.