They will fight ... feeler fights, or one picks up the other by the shell, etc. They are discovering who is the "boss". It happens and it's fine ... as long as they aren't ripping each other apart. When you say your "new one" are you ISOing your crabs?
Another reason for an attack is the lack of proteins in their diet. They ened an offering of protein in every meal. Check the safe food list for ideas.
Thats good! It's the sometimes that needs to change. They have to have proteins every day. And remember, you don't have to give them huge portions as they wont eat a lot. So for instance, if you are having turkey for dinner you can take a good size chunk, cut it into small pieces the size of say a quarter(depeding on how many crabs you have) and then freeze the rest in a baggie. You now have some ready! Also ask family members as well, to save shrimp tails if they eat those, and crab and lobster shells are good as well to give them! You go to any buffets? Take a little home with you that isnt salted or covered in spices.
Wow, I didn't realize they needed protein in every meal!! But my crabbies love raw salmon!! They will eat eggs, too, scrambled, but they didn't care alot for the chicken I offered!!!
I hadn't thought of that! I can just imagine my husband's reaction when I put shells in my purse!! LOL
Was the chicken cooked? Dried? I've not fed raw chicken, although I know someone who has done raw pork chops and the crabs do a tug of war with it. Maybe try to sprinkle on some safe crabby powders (spirulina, boost, rosehip) or even drizzle some honey on it. It may take a few times of trying chicken for the crabs to go oh hey we need to eat this LOL
Salad bars and buffets rock! Also a few of my family know to save shrimp tails and exos of crabs/lobsters for the crabs. And when I see them next they take out a bag from their freezer for me LOL.