HCA: Hermit Crab Association

AwesomeHermit wrote: ↑

Wed Feb 13, 2019 9:20 pm

I have heard of a number of owners who had their crabs for 10+ years with only a few, like two or three.

Motörcrab wrote:I don't think there is any perfect ratio of crabs. Jonathan and Kates owner Carol I believe was also a marine biologist. Here is a video I found on youtube. If you look at his tank it is nothing like what we do on here. Carol also lets him wander around the house too. In the video Jonathan is MASSIVE!
https://youtu.be/bVPnOvO2H58

We have I think 30 crabs in 4 tanks, ranging from 3 to 11 in each tank. So far all have been doing great as is so we don't plan on changing our basic care for them aside from trying new foods or changing up the decorations.

Here's the problem, it is ALL anecdotal evidence, because no one has done controlled longterm studies on the effects of single vs group. And with lifespans of 50+ years, anything that was done would be a snapshot at best. 

I've been doing this nearly a decade and I have never seen any solid evidence that they absolutely need to be kept in colonies in captivity. It's something that has been passed down since at least the mid-90s, but whoever first suggested it or why it's been repeated so many times is lost to the early internet. You'll hear "They will die without friends", which at the very least seems like something blown way out proportion, like so many other 'facts' of crab keeping. It has been made to sound so tortuous that no one ever wants to speak up and question it, let alone try it.

My best guess has been that since they are found in the wild in groups, the assumption was made they must need to be with others. Maybe it was bleed over from fishkeeping, where fish found in the wild in schools need to be with others of their kind or they display unnatural behavior and stress themselves to an early death. (For real, but you can observe this easily and there are plenty of warning signs.) I've also always been suspicious that it was a group of keepers giving themselves permission to be a little hoarder-esque in getting as many as they wanted. 


There is anecdotal proof that being kept in alone or in pairs results in longer lifespans. Obviously it's hard to gauge quality of life with these guys, but if they are eating, drinking, molting and exploring it doesn't sound any different than ones kept in larger groups. Carol Ormes had Kate for 35 years, and Jonathon is still going (as of two years ago) at 42 years and counting. There was another account of one of the early English explorers bringing one back alone that lived for 25 years. When I handled adoptions I saw many crabs that had been in captivity between 10 and 20 years, and they were all singletons and pairs. 

The question that then gets raised is - are these the hardy outliers that had the constitution to survive in the face of completely inappropriate conditions? 

I do think caution needs to be taken when it comes to immediately laying blame on other crabs in group situations where attacks are not actually observed - lone crabs do also die, they fall out of shells, drag themselves naked across tanks, decompose into nothing in an extremely short timeframe. All of these things are attributed to other crabs by novice (or simply very upset) owners. At the same time, it's hard to know what happened under all that substrate. That mangled body - was it an attack or did another crab come through after? That empty shell packed with dirt - same as above, or did the crab streak underground and do it themselves? 

We also have no good idea about diseases and parasites with these guys. The distributors that harvest them from all over the world just toss them together, which would lead to a sharing of foreign invaders both during warehousing and shipping, and once they are combined at home. Is the fact that they die often when in groups a side effect of passing infections for which some have no natural immunity? 

We are also talking about wild caught animals where there is no real way to judge their health or age. How much damage to they sustain in the collection and shipping process? In just what condition are people buying them in? Are they parasite loaded? Is it the effects of group housing, or are they just that sickly that they had no chance of long-term survival? Is it a natural old age death, or one that was exacerbated by being forced into captivity? (Molting requires more energy/resources with every subsequent molt. At some point their stored energy cannot match what is required, which is considered a natural old age death.)

A couple to a few million crabs are imported every year to the US alone. No, not an exaggeration, that figure comes from the distributors themselves - the biggest does over one million by themselves. It makes it really hard to figure out the statistics because of that. It's a minuscule percentage even being cared for properly. Of those, how many are being cared for as singletons or in groups? How many were healthy on arrival? Which ones were the natural outliers? The whole observable situation gets skewed. 

That all said, crab on crab violence is a real thing. They are opportunistic hunters and scavengers, they readily cannibalize when the reward outweighs the risk, and they are extremely strong and those claws are not for decoration. When they find another crab in a state where they cannot defend themselves, they will take full advantage of the situation. They are hard-wired for survival, so a perfect meal of crab is always a temptation. A pre-worn shell means it makes an excellent home. They don't have the capacity to understand that their needs are being met and will continue to be met - they are thinking months down the road to times of famine and scarcity. They are resourceful little dudes, it's how they survived for millions of years. 
In captivity they seem to only tolerate each other, and they don't interact except when jockeying for the best locations and resources, which as you note with reptiles, people will often misinterpret as 'cuddling' or needing to be together. 


It took a lot of self-convincing when I did it - but I have my Ruggie as a singleton. I have lost so many crabs in my colony over the years to situations where I felt it was directly due to the other crabs, that I could not bring myself to take the risk with her in a group. I won't mailorder crabs, so she is likely my once in a lifetime 'exotic'. I got her in April 2016, and she has been picture perfect since. Active, molting regularly, explorative. I see no sign of any sort of stress or her missing the group. If I had space I would like to try with my PPs, I very much regret not having done so with my first and favorite, I keep wondering if he may have still been alive today if I had.