Shell fights--when to interfere and how?

[hprmom]

I'm pretty sure we had a shell fight today, or at least some aggression. We're new to hermit crabs, our two have been pretty chill since we adopted them from a friend last week, so I was kind of freaked out! At what point is it appropriate to interfere, and how would you break a fight up or head one off?

Here's the story: Hermie arrived in a painted shell and changed out of it the first night he was home, into the only decent thing we had available, a green turbo from Petsmart. Within two days we stocked the shell shop with a variety of turbos (at least a dozen), but the second crab, Herminy (my son named them, I get the names mixed up!), never set foot on the side of the tank with the shell shop.

These two crabs have lived together for at least two years and have spent most of the week huddled together in the coco hut or corner of the tank while we worked on getting the heat up (ultratherm arrived today). Yesterday Herminy shoved Hermie in a way I hadn't seen before, and today she(?) got aggressive, crawling over Hermie and grasping at his(?) shell as if trying to flip him while he scrambled to get away. When the dust settled I agreed to let my husband put Herminy in the shell shop, then I threw a towel over the tank to give her privacy since she's the more skittish of the two.

Within minutes she changed shells--twice! Then Hermie made the mistake of joining her in the shop and shoving his butt into a smaller shell, while hanging on to the Petsmart one. Herminy was all over him. There was posturing, a stand-off, a grappling fight with legs and pincers. Hermie maintained possession of both shells by shoving his front half into the Petsmart shell; Herminy rolled them and tried to pry them apart. She even tucked herself away and waited, pouncing whenever Hermie made a move, I was afraid she would attack him while he was exposed. This went on for most of ten minutes, all of which I have on video. Eventually Herminy turned her back to check out another shell and Hermie quickly snuck back into the Petsmart shell.

Should I have interfered, at what point, and how?

Herminy finally settled on a magpie but she doesn't seem happy with it, she spent a long time settling in, I'm not sure it's a good fit (I didn't see her draw in completely far enough to seal the opening), and it's clearly heavier than the babylonia she came out of. She managed to haul it over to the dinner bowl where she promptly pigged out on shrimp and cuttlebone, all the while keeping an eye on Hermie in the shop. When he started futzing with her old babylonia, she looked like she was about to ditch the magpie and come streaking across to hit him (that's my imagination; what I saw was her coming very far out of her shell, the tiny back appendages were out). After trying on three other shells, Hermie left with the Herminy's old babylonia! And nobody took the Petsmart shell that started the fight. Both crabs appear to be struggling to get around in their new mobile homes, so I'm not certain I won't see another fight soon...

[wodesorel]

You did the right thing as you were there to watch them. The danger is when one overpowers the other and tries to physically rip the loser out of its shell because it won't back down and accept defeat. What they did was have a really good squabble, and had it progressed further you were there to step in and keep them safe. (Strangely enough, what you described sounds exactly like what my males do when fighting over a female.) Hopefully they got it out of their system and decided on a winner or that they were evenly matched.

I would probably pull the problem shell until you're able to get more of the same type. Since it caused so much trouble, it could happen again. It's also really normal for a previously worn shell to be chosen by another crab - I have several that have been in non-stop use across multiple crabs for the past 5 years. They're comfy, which is why one liked it in the first place.

It is a good idea to step in when one is chirping rapidly. A panicking and scared crab will sound like a panicked and scared animal, there is no missing it. (They can also sound mad, which is a watch and wait situation as it can go either way fast.) You should step in immediately if one grabs the other anywhere on it's body, or starts trying to pick at its body. Grabbing shells and rocking is a danger sign but the crabs should be allowed to try and work it out themselves or it might happen again when you aren't around. Shoving each other or sizing up legs is normal and is their way of figuring out if a fight is required to decide the winner of a tiff. I'm still on the fence on locking legs, I've seen it a few times and it never progressed to injury, but if they start using claws it needs broken up.

And to break up a crab fight, toss them in water. Hopefully your water bowls/pools are deep enough so you don't have to get tank temp dechlored water ready in an instant! Their instinct of "omg flood, climb!" should be stronger than their need to hurt the other.

[hprmom]

The fight reminded me so much of my dogs (no longer with me), especially the standoff! And I usually tried to let them work out their pack order. So this makes a lot of sense to me. Thanks for the detailed descriptions on what it looks like when it's time to step in, extremely helpful!

I pulled the shell, reboiled it along with a couple of "b-grade" options and added them in. The crabs ignored those but changed again, both into green turbos after lugging around magpies for several hours (I guess those are pretty heavy, even though they have the nicest mother of pearl inside!). Herminy is pretty decisive but Hermie cracks me up, always holding onto and changing back into the shell he came out of, in-between trying on others; leaving the shell shop for a short test drive and then coming right back to switch again.

I measured the babylonia they both came out of to give me an idea of what size openings they need, so I can order a few shells. We will also pick through the craft store bags again to see if we missed any other options we can give them to prevent squabbling in the meantime.

Oh--question: How deep/big should the pools be? Right now the saltwater pool is deep enough for one crab to submerge; the freshwater is deep enough for one to sit in. I don't think I could fit two fighting crabs in either one! I'm working towards a tank upgrade so I'll want to plan for better pools. THANK YOU!