Past and present fauna of Mt Owen, north-west Nelson

As well as impressive plants, Mount Owen and the Marino Mountains are also zoologically interesting.

The wet weather may have prevented us reaching the summit of Mount Owen but it did bring out the slugs and snails. We spotted a giant leaf-veined slug (Amphikonophora gigantea) beside the track on the lower flanks of the mountain. New Zealand has around 30 species of leaf-veined slug, with most only occurring here.

A giant leaf-veined slug (Amphikonophora gigantea). The pore through which the slug breathes, called a pneumostome, is visible a quarter of the length of the body away from the head.

A giant leaf-veined slug (Amphikonophora gigantea). The pore through which the slug breathes, called a pneumostome, is visible a quarter of the length of the body down from the head. Photo: Lara Shepherd.

Leaf-veined slug (Amphikonophora gigantea) with GPS [Xcm long] for scale. Next time I’ll have to go walking with a ruler!

Giant leaf-veined slug (Amphikonophora gigantea) with a GPS for scale (GPS is 16 cm long including the antenna) . Next time I’ll have to go walking with a ruler! Photo: Lara Shepherd

As well as slugs we also saw snails, or least evidence of snails. We saw shells, but no live animals, of the carnivorous snail Powelliphanta ‘owen’. This snail has been recognised as a distinct species but has not yet been formally described. It only occurs on the Marino Mountains and is considered nationally endangered.  Powelliphanta snails are only found in New Zealand and the greatest diversity of species occurs in north-west South Island. Threats to these snails includes predation by introduced mammals including rats, possums and pigs.

A shell of Powelliphanta ‘owen’.

An empty shell of a Powelliphanta ‘owen’. Photo: Lara Shepherd.

In one spot near the base of Mount Bell we saw a large number of speargrass weevils (Lyperobius clarkei), which were several centimeters in length. This species only occurs on the speargrass Aciphylla ferox, on which it feeds.

A speargrass weevil (Lyperobius clarkei) on an on the speargrass Aciphylla ferox speargrass.

A speargrass weevil (Lyperobius clarkei). Photo: Lara Shepherd.

A speargrass weevil (Lyperobius clarkei) on an on the speargrass Aciphylla ferox speargrass.

A speargrass weevil (Lyperobius clarkei) feeding on a speargrass (Aciphylla ferox). Photo: Lara Shepherd.

Another beetle we only saw on speargrass was a flower beetle (Dasytes sp.), which we saw on Aciphylla glaucesens.  Speargrasses have separate male and female plants and the flower beetles were only on the flowers on the male plants, where they were presumably eating pollen.

Flower beetles (Dasytes sp.) were abundant on the male flowers of the speargrass Aciphylla glaucesens.

Flower beetles (Dasytes sp.) were abundant on the male flowers of the speargrass Aciphylla glaucesens. Photo: Lara Shepherd.

A close-up of a flower beetle (Dasytes sp.).

A close-up of a flower beetle (Dasytes sp.). Photo: Lara Shepherd.

In addition to the fascinating species found there today, Mount Owen has provided a window into New Zealand’s prehistoric wildlife. Beneath the spectacular marble outcrops of Mount Owen are a large number of caves and sinkholes, including the Bulmer Cavern, which is New Zealand’s longest cave system. These karst features have yielded abundant fossils, including some from extinct species. Two of the most significant fossil finds are one of the most complete Haast’s eagle skeletons ever found and the remains of an upland moa which includes preserved muscle and skin. This moa specimen was one of the first moa to have its DNA sequenced, which was published in 1992. Both these important specimens are held in Te Papa’s collection.

Some of the bones of a Haast's eagle from a cave on Mt Owen now in Te Papa's fossil collection. With a wingspan of up to 3 metres this extinct species was the largest predator in prehistoric

Some of the bones of a Haast’s eagle from a cave on Mt Owen that are now part of Te Papa’s fossil collection. With a wingspan of up to 3 metres this extinct species was the largest predator in prehistoric New Zealand.

Part of a mummified upland moa, including preserved muscle, from Mt Owen. Radiocarbon dating of this specimen has shown it be over 3000 years old!

Part of a mummified upland moa, including preserved muscle, from Mt Owen. Radiocarbon dating of this specimen has shown it be over 3000 years old!

Thanks to Ricardo Palma and Bruce Marshall for help with beetle and mollusc identifications, respectively.

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