Natural history

Flora and fauna

Beech is the dominant forest tree, with red beech around the start of the Routeburn Valley on sunny, frost-free sites. Mountain beech occurs at higher altitudes within the Routeburn Valley. Silver beech competes best on the wetter Hollyford faces along with broadleaf and fuchsia. A feature of the beech forest is the abundance of ferns, mosses, lichens and perching plants.

Hairy alpine buttercup

The track passes through several avalanche paths colonised by ribbonwood, one of New Zealand’s few deciduous trees. Above the bushline between Lake Mackenzie and the Routeburn Falls are snow tussock grasslands, and herbfields with mountain buttercups, daisies, and ourisias. Bog communities, with sundews, bladderworts, orchids, daisies and bog pine occur around tarns on Key Summit.

Common fauna

The area surrounding the Routeburn Track has an abundance of native birds. There is also a significant number of introduced animals including whitetail deer in the lower Routeburn Valley, red deer throughout the forested areas and chamois about the mountain tops. Animal pests such as possums, rats and stoats are also widespread.

Yellowhead/mohua

The endangered mohua (yellowhead/bush canary) is about the size of a sparrow. It has a bright yellow head, neck and breast with the rest of the body being brownish yellow.

It is a tall-forest specialist, with strong legs and bill adapted to foraging for insects from the crevices of bark of mature trees. Mohua’s use of small tree holes for nesting and roosting expose them to greater predation than other birds, as there are no avenues of escape when a rat or stoat puts it head in the entrance.

Mohua are only found in the South Island of New Zealand. They can often be seen feeding in noisy groups with brown creepers and parakeets on the fan behind the Routeburn Flats hut or in the canopy in the first three kilometres of the Routeburn Track.

Blue duck/whio

The blue duck/whio is a unique and endangered species. It is endemic to New Zealand and has no close relative anywhere in the world.

It is blue-grey in colour with a reddish-brown spotted breast, a pale pink bill and yellow eyes and weighs about 800 - 900 grams.

Living in fast flowing streams and rivers Whio are often seen standing on rocks or feeding on fresh water invertebrates. Whio remain in territorial pairs all year. The female call is a low rattling growl, while the males call of “fee-o” gives the duck its Māori name.

On the Routeburn Track single Whio can sometimes be seen at Routeburn Flats or on the tarns north of the Harris Saddle.

Geology

The track follows close to a major fault zone which has thrown together both metamorphic and sedimentary rocks. During the Ice Ages, the last of which ended some 10,000 years ago, huge glaciers carved out the rock.

The Hollyford glacier was so large it curved around the southern end of the Darran Mountains and flowed 50 km north to Martins Bay. It overtopped the main divide at Key Summit and two lobes flowed to the south - one to Lake Wakatipu via the Greenstone Valley and the other to Lake Te Anau via the Eglinton Valley.

When the glaciers retreated they left the distinctive U–shape main valleys, smaller hanging valleys, cirque basins and residual glaciers like Donne Glacier on the eastern face of Mount Tutoko.

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