tunnels through mud to aerate the marsh

Size
Length: 3–5 cm
Lifespan
3–4 years
Diet
Detritus, algae and small invertebrates.
Habitat
Salt marshes, mudflats and estuarine banks.
Range
Throughout New Zealand in estuaries and salt marshes.
Endemism
Native
Main Threats
Habitat loss and pollution.
Population
Abundant in estuarine environments throughout New Zealand.
Conservation Status
Not Threatened
Human Risk
caution
Handling Note
large claws can deliver painful pinch if threatened or mishandled
Conservation Note
Native mud crab abundant in estuarine environments throughout New Zealand, not subject to formal NZTCS threat classification.
Te Ao Māori
Mud crabs have no specific Māori name. They are part of the estuarine environment. Their burrowing activity would have been noted. The holes in the mud. The piles of dirt. Signs of life. Of work. Of engineering. Nature’s builder. Small but mighty.
It is not a monster. It is a gardener. The Mud Crab digs. It tunnels. It aerates the soil. Its burrows allow oxygen into the mud. This helps plants grow. It mixes the sediment. It recycles nutrients. It is an engineer. An ecosystem service provider. Unpaid. Unseen. Unappreciated. But essential. Without it, the marsh stagnates. The mud suffocates. The plants die. The crab keeps it alive. By digging. Threats include habitat loss. Reclamation of salt marshes for farming or housing destroys its home. Pollution from agricultural runoff affects water quality. The crab is tolerant. But not infinite. It needs clean mud. Healthy plants. Stable tides. Diet consists of detritus, algae and small invertebrates. It is an omnivore. It eats what is available. It cleans the marsh. It removes waste. It prevents disease. It is the sanitation department. Busy. Efficient. Vital. Range covers both main islands. It is found in all major estuaries. Harbours. Salt marshes. It is widespread. Common. Successful. It thrives in the muck. In the slime. In the smell. It loves the marsh. It belongs there. Habitat is the intertidal mudflat. It builds burrows. Vertical tunnels. Up to 30cm deep. It retreats at low tide. It emerges at high tide. It feeds. It digs. It lives. It is a creature of rhythm. Of tides. Of mud. Life span is three to four years. Growth is steady. Moulting occurs regularly. It is a robust crab. Tough. Resilient. It survives freezing. It survives drying. It survives predation. It is a survivor. Of the mud.