When I first became a “crabber” I was a little stressed about my hermit crabs digging habits. Their tank always seemed messy and quite often, several of the crabs were nowhere to be seen and so I would spend ages searching for them, wondering whether they had escaped.
Once I started chatting to other crabbers in the online forums I came to realise that hermit crabs digging is a very important part of their lives. Hermit crabs naturally enjoy burrowing and climbing but also I learned that hermit crabs digging is most likely to occur when they are getting ready to molt. Now, for those of you who are unsure of the purpose of molting, it is a regular occurrence in a crab’s life cycle that is necessary in order for them to grow and even replace any lost limbs. Molting may take place about once a year in large crabs or once every few months for smaller crabs.
Some of the signs that your crab is about to molt are as follows:
1. He seems quite lethargic
2. He has started digging
3. His color has faded from a vibrant reddish brown to a dullish grey
4. He is eating and drinking a lot
5. He has developed a sort of pouch, called a molting sac, which holds water and helps to break down his exoskeleton when molting occurs
It’s very much a personal choice whether you allow your hermit crabs digging to take place in the main tank. Some people prefer to place their crabs in an isolation tank that is smaller, with lots of moist sand or eco earth, water, food and drink and rocks or shells in which to hide. However, the isolation tank does need to have a similar temperature and level of humidity to that of the main tank.
Your hermit crabs digging should take place underneath the substrate or layer of sand. If this is not happening you are most likely using the wrong type of substrate. Gravel or wood shavings do not make for good substrate, since they can get into a crab’s shell and cause damage. Even with the right conditions, however, some crabs may choose to molt on top of the substrate and this is known as surface molting. If this happens, then it is advisable to move the crab to an isolation tank, because a newly molted crab is very soft immediately after molting and could be vulnerable to attack from other crabs. The molting process can take several weeks or even months, from start to finish, so your best course of action is just to let your crab get on with. He knows what he’s doing! Just remember to keep him supplied with food and water so that he is in tip top condition once he emerges in all his glory.
Never be tempted to interfere with your hermit crabs digging because it is an essential part of his lifecycle. He can appear quite timid once he has finished molting and it can take a couple of days to week for him to fully harden and become active again and it may take even longer for his former personality to re-appear.
I will just mention that after your hermit crabs digging and molting has taken place, it can be easy for a new crab owner to think that their crab has died instead of molted. You see, if you come across a crab that looks as if it has fallen out of its shell, you need to examine the shell carefully to see if there is actually a small crab snuggled inside. What happens here is that once your hermit crab has molted, the soft abdomen will not fall out of the shell, only the hard exoskeleton will be shed and can be found laying on the surface. So don’t freak out, just take a breath, and check inside the shell.