Wetland animals

Wetland habitats are diverse places. They support an enormous range of animals from microscopic communities to some of Aotearoa’s largest birds.

Zooplankton – the tiniest aquatic organisms

Zooplankton are really, really small animals. The biggest are only 5 mm long, and a microscope is needed to see the smaller species. Zooplankton eat algae and bacteria in freshwater systems and they are food for aquatic insects and small fish. Although zooplankton are likely overlooked when planning wetland restoration projects, they are a really important part of wetland food webs. Water quality is important – changes in hydrology, nutrient levels, temperature and pH affect these tiny creatures. Riparian planting helps with water quality and it shades the waterway, cooling the water and protecting zooplankton from UV.

Freshwater macroinvertebrates

Freshwater macroinvertebrates include tiny creatures that live under rocks or leaves, in the sediment or in the vegetation along the edges of the wetland. Some creatures like freshwater snails and mussels (kākahi, Echyridella menziesi) spend their entire lives in the water. Aquatic insects like dragonflies and mosquitoes live in the water during their larval or nymph stages but out of the water as adults. Macroinvertebrates are an important food source for fish, birds and other animals. They also help to recycle nutrients in aquatic environments.

Native freshwater fish

Aotearoa has around 50 endemic freshwater fish species, but there are more that have not yet been formally identified. Lots of native fish species are secretive or live in remote areas. One example is the Tarndale bully (Gobiomorphus alpinus), which lives in a few small subalpine tarns (small glacial wetland lakes) in the South Island. Other fish that live in wetlands are mudfish (hauhau, waikaka, kōwaro, Neochanna apoda and other species) and the giant kōkopu (Galaxias argenteus).

Kōura

Kōura are freshwater crayfish (Paranephrops planifrons and P. zealandicus). They live among rocks, tree roots and submerged vegetation. Kōura are omnivores – they eat plants, other animals and detritus (dead things). They are also food for fish, birds and humans. Kōura have pincers on their front legs for fighting each other and the predators that are trying to eat them.

Tuna

Tuna (longfin eel, Anguilla dieffenbachii) have a mysterious life cycle. They breed only once at the end of their life cycle. In the autumn, adult eels leave the wetlands, rivers and streams and head for the ocean. From there, they make a long journey to a place somewhere in the South Pacific Ocean. Scientists think the spawning grounds may be close to Tonga. The larvae float on ocean currents back to Aotearoa. Once they’ve returned, the larvae change into glass eels (juvenile tuna) and then become elvers (small adults). They make their way to freshwater and grow into adults. Elvers feed on macroinvertebrates, and tuna will eat kōura if they get the chance. Tuna also feed on small birds and ducklings.

Birds

Some of the most recognisable animals in repo are the birds. A whopping 30% of Aotearoa’s birds are wetland species. Ducks are commonly found in wetlands. For some species, like kuruwhengi (New Zealand shoveler, Anas rhynchotis variegata), freshwater wetlands are their primary habitats.

Shags are also wetland inhabitants. Aotearoa has 12 species including kawau (black shag, Phalacrocorax carbo novaehollandiae), kawaupaka (little shag, Phalacrocorax melanoleucos) and kāruhiruhi (pied shag, Phalacrocorax varius). Shags are top predators and eat small and medium-sized fish.

Ruru (morepork, Ninox novaeseelandiae) also have ties to wetlands. Like tūī (Prosthemadera novaeseelandiae), kōtare (kingfisher, Todiramphus sanctus) and many other native birds, ruru fly across awa, roto, bush areas and repo. Ruru eat insects and smaller creatures, kōtare eat small fish, insects and kōura, while tūī prefer nectar and the occasional insect.

Interconnections

So many animals whakapapa to repo ecosystems. Aotearoa has lost 90% of its wetlands in the last 150 years, so efforts to restore remaining wetlands are crucial. Work to restore water quality and to minimise introduced and pest species can have positive impacts across the habitats and their associated food webs.