Within 4–8 days, the larva moults numerous times, finally ending with morphological changes that presumably include the further development and increase in size of the cephalothorax.

The larva then undergoes metamorphosis to the first juvenile instar, and changes its planktonic life to a benthic one (living on the sea floor).

The second moult marks the beginning of the third juvenile stage, the animal now has the appearance of the adult, with a carapace length of approx.

The juvenile animals live in shallow water in winter, between rocks in coastal kelp forests.

They spend the summer on small rocky reefs at a depth of only about 4 m. After this time, they reach a carapace length between 6–13 cm, with no noticeable sex-specific differences.

Migrations generally take place in autumn,[2] with some crabs covering over 100 mi (160 km) in 8 months.

From a 1992 study done in Galicia, seaweeds from the Laminariaceae, Corallina spp., molluscs, the gastropods Bittium spp., Trochiidae, the bivalve Mytilus spp., echinoderms, and others were observed as part of the diet of this particular species.

[1] M. squinado is the subject of commercial fishery, with over 5,000 tonnes caught annually, more than 70% the coast of France, over 10% off the coast of the United Kingdom, 6% from the Channel Islands, 3% from each of Spain and Ireland, 2% from Croatia, 1% from Portugal, and the remainder coming from Montenegro, Denmark, and Morocco,[6] although official production figures are open to doubt.