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Quick Guide

Acari (mites)
Amphipoda (landhoppers)
Araneae (spiders)
Chilopoda (centipedes)
Collembola (springtails)
Diplopoda (millipedes)
Isopoda (slaters)
Insecta (insects)
Mollusca (slugs & snails)
Oligochaeta (earthworms)
Onychophora (peripatus)
Opiliones (harvestmen)
Turbellaria (flatworms)


Dr. Maria Minor
Wildlife & Ecology Group
Massey University
Palmerston North
New Zealand

+64-06-356-9099 ext.84833

New Zealand Terrestrial & Freshwater Biodiversity Information System (TFBIS). Find out more...

New Zealand Soil Fauna

Native podocarp forest of the South Island, one of the few remnants.

The soil and leaf litter make up a unique habitat that supports a rich and diverse life. The soil is a matrix of myriad solid mineral particles, decomposing organic matter, and pores filled by water and air. The soil atmosphere is always very humid. Temperature and moisture extremes are attenuated in the soil.

Soil and litter animals avoid light and many of them have poor vision, using instead the senses of touch and smell. Most soil animals absorb and lose water freely through their skin, and so depend on water-saturated atmosphere for their existence. If the soil dries out, the animals migrate away from unfavourable conditions, or persist as resistant eggs. Soil animals play a major role in the breakdown of wood and dead leaves, recycling of nutrients back into the soil, and the release of nutrients to plants. Digging into the soil, soil invertebrates mix together organic and mineral matter, and improve soil aeration, structure, and fertility.

Southern beech forest, South Island of New Zealand.

Unlike temperate and boreal forests of the Northern Hemisphere, New Zealand forests are structured more like the rainforests of the tropics, with their suspended gardens of epiphytes, damp climate, and evergreen vegetation. Wherever organic matter accumulates - in leaf litter on the ground, in the clumps of epiphytes in the canopy, or on mossy tree trunks, soil animals can be found. Decaying logs and dead tree branches provide another important habitat on the forest floor. The characteristics of the soils, the form of the landscape, the vegetation and the history of disturbance all have considerable influences on the soil fauna, its biodiversity, species composition, and the distribution of species in space and time.

Mixed beech/podocarp forest, North Island.

Alpine scree, South Island.

“New Zealand has a relatively small number of indigenous flowering plants and vertebrate animals by tropical or continental standards. This is partly because our isolation from continental landmasses limited large-scale recolonisation by these groups after the global extinction catastrophe of 65 million years ago. It is also partly the result of a long period of submergence between 60 million and 30 million years ago, when up to four-fifths of the landmass sank below sea level, leaving just a few islands (Cooper and Milliner, 1993). The ice ages of the past two million years also had an effect, reducing habitat and fragmenting populations into ecological 'islands'. These factors limited the number of major plant and animal groups in New Zealand, but they also contributed to the uniqueness of the surviving groups. Cut off from the rest of the world, evolution took an eccentric course here, leading to a high percentage of endemic, or unique, species. This high rate of endemism is what makes New Zealand's biodiversity both special and highly vulnerable.”

The long-term geographical isolation of New Zealand contributed to its unique and diverse soil fauna. Colourful flatworms (phylum Platyhelminthes), slugs and snails of all sizes (phylum Mollusca), and numerous crustaceans, insects, spiders, myriapods and mites (all members of the phylum Arthropoda) make up the populations of New Zealand soils. Some exotic animals include giant blue springtails (Holacanthella spp, phylum Arthropoda, class Collembola), giant bioluminescent native earthworms (Megascolecidae, phylum Annelida), and the living fossil – the peripatus (phylum Onychophora).

From: The State of New Zealand’s Environment 1997, published by The NZ Ministry for the Environment and GP Publications, Wellington, New Zealand. Click here to read The State of NZ Environment 1997 online.

On giant New Zealand invertebrates:

Box 9.4: Jurassic giants

Gigantism evolved in various groups of New Zealand animals (Daugherty et al., 1993). The giant birds, such as Haast's eagle and the moas, are extinct but many invertebrate giants still hang on in the face of rat predation and habitat destruction. Most are confined to isolated locations or rat-free islands (Meads, 1990). The world's heaviest insect is among them - the giant wingless cricket, or weta, of Little Barrier Island. At lengths of more than 8 cm and weights of up to 70 g, this relative of primitive grasshoppers is as heavy as 4 or 5 mice. Known to Maori as the wetapunga or 'god of ugly things', it is the largest of our dozen giant weta species (Deinacrida spp.). It has a docile temperament and lives high in the tree tops. In Jurassic times, 190 million years ago, giant wetas were widespread around the world. Now New Zealand is their only holdout.

While all seven species of the smaller tree weta (Hemideina spp.) are quite common, the giants face an uncertain future. All but one, the alpine scree weta (D. connectans) of the South Island mountains, are listed as threatened. Another group of wingless crickets, the large elephant or tusked wetas, is also under extreme threat. Named for their 2 cm tusks, these wetas can grow up to 8 cm long and live in ground burrows. Three species have been discovered. One is confined to a few hectares of forest on Middle Mercury Island, near the Coromandel peninsula, one is scattered in parts of Northland and one was recently discovered in the Raukumara mountains in Bay of Plenty.

Myriapods (millipedes and centipedes) are a less flamboyant class of arthropods than the insects, but they also have monsters, such as the giant pill millipede (Procyliosoma tuberculata). Unlike its smaller relatives in Europe, which were swallowed as folk medicine, this pill would be hard to wash down with a glass of water. Females can grow up to 5 cm long and 2.5 cm wide. They feed on rotting leaves and are widespread in the North Island and northern South Island. They reach full size, however, only on rat-free islands. Then there is the giant centipede (Cormocephalus rubriceps) which, at 25 cm, looks like the caterpillar from Hell with its armour-plating and jointed legs. However, mothers are protective of their young, even carrying them around. They capture prey (usually insects, spiders, snails and slugs) with claw-tipped pincers which inject a lethal poison. They can even kill small lizards. Though still present in the North Island, full-sized ones are only found on rat-free islands (Meads, 1990).

Spiders belong to the third class of land arthropods, the Arachnids. Our largest, the Cave spider (Spelungula cavernicola), may be a 'missing link' between primitive spiders, which arose 350 million years ago, and the modern 'true' spiders. Its 3 cm body and 30 cm leg-span have startled more than one speleologist in the limestone caves of the Tasman Region where it lives. It is very rare and is the only spider protected by the Wildlife Act 1953 (Faulls, 1991). Another group of indigenous giants confined to the Tasman Region are the giant red flatworms (Geoplana spp.), which can reach lengths of 20 cm. They hunt by smothering their victims (mainly slugs and snails) in slimy mucus. Once abundant, they are rarely seen today.

Far more widespread are the nine species of giant land snail (Powelliphanta spp.) whose colourful shells can be up to 10 cm in diameter. Some of these snails have human-scale lifespans, taking up to 15 years to reach maturity and living 40 years or more. Their reproductive rates are correspondingly low. The giant snails belong to the oldest family of carnivorous land snails on earth, having originated about 200 million years ago. They prey mainly on earthworms, slugs and other snails. Although they are scattered across habitats ranging from forest to alpine grassland, they have been driven into confined areas and nearly all are listed as threatened. Related to the giant snails are the giant leaf-veined slugs (Pseudaneitea gigantea) which, at 15 cm, are the largest of our native slugs. These have also been driven into relic areas of forest and tussock grassland.

From: The State of New Zealand’s Environment 1997, published by The NZ Ministry for the Environment and GP Publications, Wellington, New Zealand. Click here to read The State of NZ Environment 1997 online.

Conserving Soil Biodiversity in New Zealand

Alpine grassland of Canterbury, South Island.

The New Zealand landscapes, once largely covered in forest, have been extensively altered by human activity. Two-thirds of New Zealand forests have been cleared, and the land is now used for intensively managed cropland and pasture grassland. Many species of the original forest soil fauna did not survive land conversion and disappeared from agricultural ecosystems. In return, many introduced soil species have become established in New Zealand, replacing the indigenous soil fauna in human-modified environments. Today, most of the common soil animals found in farmland, urban parks and suburban gardens are introduced species. If you do not know whether the soil animal you found is native or introduced, as a rule, a species found in undisturbed land well away from human habitation is probably native, whereas one found in a garden or a city park is most likely introduced. There are many exceptions – some truly native species have invaded agricultural systems and urban environments over the last 150 years, and in some areas introduced species have invaded forest and alpine soil ecosystems.

Little is known of the requirements for the survival and health of New Zealand’s endemic invertebrate fauna. The clear-cut of the forest and the conversion of woodlands into farmlands may have contributed to the loss of soil biodiversity. To a lesser degree, the removal of dead trees from paddocks eliminates important habitats for soil invertebrates. We have limited knowledge of the extent to which native soil biota is able to survive in small isolated remnants of native bush within agricultural areas. There is evidence, however, that indigenous soil fauna can persist cryptically in small patches of native vegetation even in urban environments. Introduced to New Zealand ground-dwelling mammals pose another major threat to indigenous soil fauna (the endemic vertebrate fauna of New Zealand consisted of birds, bats and reptiles only). Introduced by humans – possums, stoats, pigs, rats and mice routinely prey on soil invertebrates, while larger mammals such as deer and goats change or destroy the habitat and food sources of native species. Rats and mice, which are omnivorous generalists and breed to high densities in native New Zealand forests, are the invasive species most likely to have an adverse effect on soil ecosystems. Indeed, many groups of soil invertebrates – insect larvae, earthworms, beetles, wetas, snails, centipedes, etc., have been found to be consumed in large numbers by rats and mice.

A square meter of forest floor may be inhabited by hundreds of species of invertebrates, many barely visible to the naked eye. These are the organisms whose identities and life cycles are often unknown. Many native species of New Zealand soil fauna are still undescribed, and the intricate relationships among individual species remain 'terra incognita'. Given the enormous diversity of soil animals, the number of soil zoologists and soil ecologists in New Zealand is pitifully few, particularly if compared with such well developed areas as bird and mammal ecology. There are many gaps in our knowledge, and when little or nothing is known about ecosystem roles and the natural history of many species, you, the visitor, are encouraged to fill these gaps.

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