Shore Crab Uncertainty

Common shore crabs on Vancouver Island are usually pretty easy to identify. Colour isn’t always a good way to separate out the Green Shore Crab (Hemigrapsus oregonensis) from the Purple Shore Crab (Hemigrapsus nudus) since both have some variability in colouration. The more reliable way to tell the two apart is to look at the legs – Green Shore Crabs have noticeable hairs on their legs while Purple Shore Crabs tend to lack hairs (hence the nudus).

So what happens when you find a green coloured shore crab without hairs on its legs?

Shore Crab
This little green shore crab was out on the middle of a sandy beach at Miracle Beach Provincial Park on Vancouver Island, British Columbia.

This crab was out in the middle of the sand at Miracle Beach Provincial Parknot a particularly safe place to be with all of the sea gulls and toddlers around. Horribly exposed, it was a long way from the shelter of the cobble beach where you’ll find both species of shore crabs readily. Just waiting for the tide to come in.

Shore Crab
Normally easy to identify by the presence or lack of hair on the legs this green shore crab presents a problem due to a conflict between colour and appearance.

Green or Purple doesn’t really matter in this case – especially when survival is at stake. I hope it managed to find a place to hide until the tide turned.

3 comments

  1. Could it have something to do with either just getting ready to shed, or having just shed its shell?

  2. I think that you’re right on this Dave – it certainly does have a soft look to it although I admit that I didn’t touch the crab to see if it was a fresh moult. I don’t usually rely on colour alone but I’m definitely leaning towards Green (H. oregonensis) on this one!

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