How Paddle Crabs Burrow
Paddle crabs are found throughout New Zealand, from almost semi-tropical Northland beaches to the very much colder beaches of Stewart Island in the far south of the country. They live on sandy bottoms in estuaries and surf beaches alike.
During the day most crabs remain hidden in temporary burrows emerging soon after sunset to hunt for bivalve molluscs. In turn they are eaten by over 30 different species of fish. Living as they do in an open environment the crab can either swim for cover (not often its first choice), stand and fight, or burrow out of harms way. Larger crabs (that is those with shells more than 7cm wide) are quite aggressive, and will confront their enemies and lunge upwards with the long chelae (claws) held upwards and outwards. But smaller crabs will burrow backwards quickly out of sight.
A short period is spent searching for a suitable piece of sand to burrow into. The crab tests the sand with its first pair of walking legs, it may even take a bit of sand up to its mouth to check out the 'taste',in case there are any other paddle crabs buried there.
Satisfied, the back paddle-shaped legs are inserted into the soft sand, and with a wiggle and a wriggle and a push of the body forwards to help create a depression, and an average of some 6 seconds later the crab is buried.
Once the sand has covered the body the chelae are folded in against the body, so only the crab’s eye stalks peep out. Larger crabs will also burrow to hide during daylight – they take a little longer – up to 24 seconds.
This sequence of still frames from one of NHNZ Image’s clips shows the burrowing technique of paddle crabs. Paddle crabs, many other species of crabs and much marine life are available for purchase for you production, check out the library’s website, or contact us for further information.