Stephens Island, New Zealand

Stephens Island is at the northern most tip of the Marlborough Sounds in the South Island of New Zealand. It lies two kilometres to the northeast of Cape Stephens, the northernmost point of D'Urville Island. The Māori call the island Takapourewa but Stephens Island is the commonly used name. The island is just 2.6 square kilometers (1 square mile) in size, but rises 305 meters (approx. 1000 ft) high from the sea.

A lighthouse keeper's cat, "Tibbles", is infamously known for killing all Stephens Island Wrens and causing the extinction of the species in 1894. However, much of this account is an urban legend; while the species was killed off by the lighthouse personnel's cats, which had gone feral, this happened not in 1894, and the island was only the last refuge of the bird, which had become extinct on the mainland many centuries earlier due to Polynesian rat predation (see Galbreath & Brown, 2004).

The island has never been invaded by mammalian pests. Today, the best known residents of Stephens Island are the tuatara - the island is a sanctuary for this rare type of reptile, now extinct on the mainland (except in tightly controlled reserves including ecological islands).

Takapourewa is internationally important for nature conservation. While most attention has focused on tuatara, the significant and unique factors include:

• Endemic species – those found nowhere else, either because they evolved here or because they have become extinct everywhere else – such as Hamilton's Frog, perhaps the rarest frog in the world
• Unusual species such as tuatara - members of the genus Sphenodon being the sole survivors of a group of reptiles that otherwise appears to have been extinct elsewhere in the world for more than 60 million years
• Rare species – such as the striped gecko and Cook Strait click beetle that are only found in a handful of other places, and for which Takapourewa is a stronghold
• Common species in unusual abundance – such as the more than one million seabirds, vast numbers of wetas and darkling beetles and many more
• Outstanding ecological features – Takapourewa has been calculated to have the greatest density of top predators both in numbers and biomass of any piece of land on Earth (calculated by the author and published in New Scientist C1996)
• Takapourewa is a part of a complex ecosystem that includes a vast area of ocean. An enormous number of seabirds link this small (154 ha) island to a vast marine ecosystem. The sea provides nutrients, the seabirds carry these to the island and Takapourewa provides a sanctuary for nesting birds, free of mammalian land predators.

In natural character, Takapourewa is a rugged landmass dominated by maritime influences. Visually the island is connected to the adjacent larger D’Urville Island, and Takapourewa is the largest of the family of islands, islets and rock stacks that characterise this south-western side of Cook Strait. The island has been extensively modified by land clearance and farming, but retains much of its wild natural character. From sea level the lighthouse is a prominent visual feature, while from the air the cluster of buildings and farmed landscape are obvious.

The surrounding sea is rich with marine life, albeit strongly modified and depleted by fishing, and historically by hunting of whales and seals. The island overlooks one of the great whale migration routes. Marine mammals such as New Zealand fur seals and various dolphin species are seen around the island.

This is an area of strong winds (mean annual wind speed 14 knots), strong currents and broken restless seas. The island also harbours strong gradations of weather between the often cloud-covered summit and the wave-lashed shores. There are also distinct differences between the relatively more exposed western and the less exposed eastern shores. Rainfall averages a modest 800mm.

Takapourewa is an area of natural noise rather than natural quiet, with the wind and the abundant birdlife dominating.

References

• Galbreath, Ross & Brown, Derek (2004): The tale of the lighthouse-keeper's cat: Discovery and extinction of the Stephens Island wren (Traversia lyalli). Notornis 51(4): 193–200. PDF fulltext
• Stephens, Cielle (2004) : Plant succession, ecological restoration and the skinks of Stephens Island/Takapourewa (Thesis (M.Sc.)--Victoria University of Wellington) PDF