The Curious Critter for April/Paengawhāwhā is kōura/kēwai. When the leaves begin to fall from trees, and dew clings to them in the early morning, these small freshwater crayfish might be spotted carrying their eggs. Read on to learn more about this taonga and valued mahinga kai species.
Kōura (also known as kēwai) are small, brown freshwater crayfish. They have a set of large pincers, a hard exoskeleton, and a tail to help them move quickly in water. You can find kōura in almost any freshwater – from streams and rivers, to ponds, lakes and wetlands.
In autumn, the kōura begin to breed. The females will lay berry-like eggs, and carry them around under their abdomens for about 28 weeks (or 19–20 weeks in a second spring–summer breeding period).
From these little eggs, tiny versions of the adult kōura are born. They cling to their mum with their mini pincers until they are 4 to 10 mm long. As they grow, they get too big for their exoskeleton shell and shed it before growing a new, bigger one. They can moult up to nine shells in the first few years of life, reducing to about one moult per year when they turn four. They can take up to four years to become adults. The young kōura are most vulnerable to predators while their new shells are soft and growing.
Illustration of kōura
Tuna (eels), shags, whio and some introduced fish prey on kōura. They are a favourite snack for trout. On land, rats, stoats, kingfishers and kiwi will have a taste if they can catch them. Kōura eat a scavenged smorgasboard including fish, plants, snails, mayflies and mayfly larvae. By gobbling up waste from the streambed, they are an important cleanser of the ecosystem, filtering sediment as they go. They use their large claws to catch their kai and chop it up. Both the northern and larger (and hairier) southern kōura are threatened species, largely due to water quality issues. Improving the health of waterways is a key way to help kōura populations thrive.
Kōura are most active at night. If you go down to a stream with a torch, you might be able to spot one! Can you see what it might be eating? Taking note of species you can spy in (and around) the water is a great way to add to the picture of biodiversity you are building alongside your eDNA results.