decorator crabs

While we are on the topic of crabs, I can't finish February without a brief mention of my favourite groups of crabs. I speak of decorator crabs, a group of spider-like crabs that camouflage themselves with all manner of other marine life.

The most common rocky shore decorator crabs are often called seaweed crabs. This is because they 'decorate' themselves with little bits of seaweed from the tide pools in which they live. This decorative coat of seaweed is a most effective camouflage.

However, if you are patient enough to sit quietly and watch a tide pool for a while, you may be lucky enough to see these charming crabs. This is because decorator crabs detect movement rather than recognise shapes. When you first approach a tide pool a crab will see you coming and freeze. If you sit still it will soon feel safe and continue on its routine.

a seaweed crab 'decorates'
itself with seaweed
(click thumbnail for full image)

this small decorator crab has camouflaged itself with tiny
colonial animals called bryozoans
(click thumbnail for full image)

Over the next few months I will look into more of our common rocky shore crabs. In particular I will be looking at seasonal events, such as the times when females carry eggs and the times when crabs shed their shells.

To date I have concentrated on beaches and spent a little time on rocky shores. In the coming months I also hope to spend some more time in local salt marshes and introduce the visitors to this web site to some southern Australian sand dune plants