Cohabitation with other inverts, specifically land hermit crabs.

[soilentgringa]

Hello,

I'm an admin for a hermit crab forum and would appreciate some knowledgeable input from experienced insect and arachnid hobbyists.

Someone posted today that they are researching keeping praying mantises with their land hermit crabs.

Since hermit crabs require tropical conditions (deep moist substrate, humidity and temps of at least 80F/80%, and need access to both fresh and marine grade saltwater), some feel that insects or other arachnids would be just fine sharing space with them.

Land hermit crabs aren't generally hunters; I've observed mine picking live isopods up and eating them, but that is probably just due to the opportunity, since they don't have space to escape from the crabs.

The crab tanks are anywhere from 29 gallons and up, depending on species and number (10 gallons per crab the minimum recommendation for a "large" hermit crab).

While I personally do not agree with keeping species together that don't have overlapping habitats in the wild, or that don't need to be in close quarters together, I would enjoy input on the subject. The mantis species in particular was the Carolina Mantis (stagmomantis carolina) which would not live anywhere near land hermit crabs native territory. (There are no land hermit crabs native to the U.S. at all, with the exception of the southernmost tip of Florida and the Keys; coenobita clypeatus.)

Thank you!

 

[Jacob Ma]

Is there any way some photographic evidence of the enclosure can be presented? Or at least a pretty good description of a look at the enclosure? I'm no super experienced keeper, but it seems like a pretty interesting concept. One thing I would have to say is that mantis droppings do not go well with water at all, as they will most definitely pollute the water and "fungify" in about a day. This is usually solved through decomposing organisms breaking down the waste into the soil or cleaning waste out of enclosure once or twice daily or every other day. But even then, some of the organisms needed in breaking down wastes are anaerobic bacteria and fungi, which I'm pretty sure hermit crabs don't appreciate too much.

I'm also afraid that mantis aggressiveness/defensiveness may interfere with the hermit crab's generally passive life, causing an unsightly interaction between the two. The insects that need to be fed to the mantis may also pollute the hermit crab's environment from uneaten remains or once live insects that may drown or die from the water/unsuitable environment that they are introduced to. Mantises can be force-fed food, but from my experience specifically Carolina mantises are active hunters and not optimistic carnivores.

 

[Ranitomeya]

I wouldn't recommend keeping hermit crabs with inverts that molt unprotected and out in the open as they will most likely try to take advantage of a defenseless food source. If the mantis were to molt on decorations within the enclosure, a hermit crab could easily smell it and climb up the decoration to get at it.

 

[soilentgringa]

This is one of my personal hermit crab enclosures to give you an idea. 55 gallon tank, 7 crabs ranging from small/medium size to medium/large.

Beneficial insects like springtails and isopods are common in "crabitats". I have a separate tank that I breed the armadillum in specifically for the purpose of cleaning up moldy food the crabs hide, and other waste.

Substrate is 5:1 ratio of silica based playsand to Eco Earth, kept at sandcastle consistency with dechlorinated marine grade saltwater (Instant Ocean), to facilitate tunneling and molting. Since crabs bury underground to molt, the proper sub is crucial to their survival.

They have to have dechlorinated fresh water and saltwater as well. A friend mentioned earlier that mantids were not able to survive in such an environment due to the saltwater.

The crabs are scavengers. Some crabbers have stated that they never see theirs eat the isopods, while some have. It is not recommended to put any sort of live crickets or grasshoppers in because they will breed and annoy the crabs.

Generally we advise people against housing anything with the crabs because they just require very different setups and space is an issue. They may live near each other in the wild but wouldn't hang out within a couple of feet of each other constantly.

 

[Jacob Ma]

The only thing about that crabitat is that, mantises prefer a taller living space over more surface area. Unlike crabs, mantises require much taller enclosures to stimulate proper molting when it is time for them to do so. I thought it would be pretty interesting if instead some other "peaceful" species of crab coexisted with the hermit crabs, and given that they both may require the same environment would make it a lot more suitable for both animals. On beaches in my area, I have seen praying mantises living in the grassy storm borders of the beach and miniature land hermit crabs scuttling along the shorefront, but otherwise praying mantises are generally nowhere near hermit crabs.

Carolina mantises like some humidity, but they do not like to live in places right next to water as they "fear" drowning. As @Ranitomeya said, mantises are most vulnerable when molting, which crabs generally do go after very vulnerable individuals when they hunt.

 

[soilentgringa]

Thank you for your input!