HCA: Hermit Crab Association

Greetings Crab Helpers!

I have a rather large hermit crab, about the size of my (tiny person's) squished up fist. We adopted him last spring when someone was looking to re-home him. "Mr. Crabby," molted as expected around August 2015, which took close to 6 weeks. I read that he may only molt once a year. I was surprised when he went underground and stayed there again in late February, but I figured my timing guess was off and maybe he molts every 6 months. I read that he should not be disturbed while molting, so I do not disturb him any time he is not on the surface. However, I have not seen evidence of a molt, and he emerged one night and has gone back under.

We intend to get this lonelyheart a friend, and thought that being solo could be part of his problem. However, it was winter and crabs couldn't be transported, and I couldn't find any in my area in need of adoption. And now, I don't want to bring another crab into the tank while this one is underground and may not be in a good, healthful position.

What could be going on with this guy? Is this normal? This creature gets little to no sustenance. He ate very, very little even the month before he went underground. Temperature and humidity are ok. Most of substrate is sand, with a portion coconut husk, as mold was a problem last summer. He gets a large size water area, and some salt water in a tiny bowl. I offer him lots of good, fresh food from the list you provide. I sometimes put the dehydrated shrimp type food that came with him, just to see if he'll eat that, but he generally doesn't.

Any insight would be appreciated. We really want this guy to be healthy and happy.
Thank you,
Heather

The larger the crab, the more unpredictable they are. My large guy came up from a long molt in mid-January and disappeared below again about four weeks ago...what he's up to, only he knows. Is it possible your crab is coming up at night to eat and drink a bit before tunneling back under? No tracks on the substrate? Try placing a bit of food, i.e., a bit of dry mix, in the middle of the food dish, not spread out, and see if it has been disturbed after a day or two.

How large is the tank and how deep is the substrate? Is it maintaining its sandcastle consistency? For a large crab, a depth of 8" is as shallow as you'd want to go. Is the temperature holding at 75 degrees or higher? Humidity 80% or more?

One thing you mentioned is that you have a large FW pool but only a small SW dish. Crabs need to be able to fully submerge in both types of water to enable them to regulate their body chemistry -- some of the minerals they would get by dunking themselves into the ocean they get from the SW pool in the tank. If your big guy hasn't been getting the right mineral mix, he may be out of sorts as a result. Substitute the small SW dish for a container deep enough for him to soak in and be sure that you're using a mix designed for saltwater aquariums, i.e., Instant Ocean, Coralife, Seachem Marine, added to dechlorinated water.

Thank you. I will get a new SW area as soon as he comes up. He is not coming up at all...except for that one night. It is so odd and concerning. There is always sand in the food dishes when he is up...and just to be certain, I raked the ground so it would be clear. The substrate is nearly 8 inches. I will add to it. It is way more than he had in his former environment, and about 5 inches clearly covers him. The sand is sandcastle consistency...except likely in his immediate area. I sprinkle lots of water in and can mix it together for much of the area, and I can mist where he is (doesn't penetrate far), but I can't disturb his area or pour water over him...that I know of?
Temperature is good. Humidity has been challenging this winter, but keeping it as high as possible. Closer to 75%. I will give it an extra spray each day.

Thank you for your response!

Over 70% is safe for most species, though many crabbers note more activity around 80%. Many also notice more activity with temps at or above 80F as well. (safe zone for PPs is 75-85F, Es 80-90F, other species may have slightly different ranges)

However, some crabs just like to dig. This may be the case with your guy, though a molt 6 months later -even for a large guy- isn't unheard of either. Sometimes they molt sooner than we expect to repair some injury or make up for lost time if they were previously in poor conditions before.

On a side note, I actually find the opposite to be true. The larger the crab, the easier it becomes to predict when they're going to molt. This has just been my experience though. As I believe Kelly says, "Crabs are weird!"

Thank you for your responses! He has emerged in the last week. But...he goes back underground every day. I forgot that he had been doing that before he just stayed under again. Perhaps greater efforts to increase humidity and temp helped, perhaps it was just his time. I think I will post on the fact that he digs under every day in the behavior section. That doesn't seem like normal behavior for most. And, it wasn't usual for this crab until a couple months ago.
Thank you again!
Heather