Safety and Survival Of
Hermit Crabs as Pets
Hermit crab owners must be extra-vigilant guardians over these special pets, and keep them safe from particular dangers. Hermit crabs naturally enjoy a relatively long lifespan in the wild (20-40 yrs), however, they may have to face starvation following injury, being evicted from or outgrowing their shells, or not finding a suitable shell, with the eventual fate of desiccation or being eaten, or being attacked or dying during a molt. Although they will usually avoid many of these natural fates as pets, their lifespan is most often dramatically reduced. Hence, it is crucial to be aware of the things they are vulnerable to in our households, and protect them as much as possible, so they may enjoy comfort and a similarly long lifespan as pets. Here is a summary list of dangers to look out for in order to effectively “crabby-proof” the crabs' environment.
Chemical exposures –
In the wild, there are natural elements which are toxic to hermit crabs, pine and evergreens, citrus plants and stems, metals, etc., however with human contact, the number of dangerous chemicals and toxins they could be exposed to increases tremendously. Beginning with the painted shells, they most often are forced into to make them more attractive for sale, hermit crabs are exposed to the chemicals in the paint by eating it when it chips at any time while wearing the shell, or being placed in the shell when the paint is still wet. The paint may be branded non-toxic but that label refers to toxic effects on human beings - when hermit crabs eat the paint it is poisonous to them. Additionally, decorative items sold for hermit crab tanks, including decorative colored sand have dyes which may leak in a humid environment and also paint which may chip and get eaten. When hermit crabs molt, they have soft vulnerable bodies which are now unprotected against the chemical dyes present in brightly colored sand. Hermit crabs will often be seen eating sand, so they are exposed even when they are not molting.
Food is another potential source of chemical exposure as commercially processed hermit crab food pellets often have preservatives such as ethoxyquin and copper sulfate which are preservatives or insecticides. As invertebrates, hermit crabs are vulnerable to many chemicals which are used to kill insects. This is why many hermit crab owners avoid commercial food pellets altogether, because it is not always easy to determine which preservatives have been included, how the food was processed, or which chemicals are harmful to the hermit crabs.
Even a fresh food diet is not without dangers as pesticides are commonly used to grow crops for human consumption. The pesticide levels deemed acceptable for humans do not necessarily apply to invertebrates. Therefore, organic food or food collected naturally from the wild is preferable to regular store-bought, farmed produce. The water used in water dishes and to mix the substrate are another source of poisoning for hermit crabs. Heavy metals and chemicals such as chlorine, chloramines and fluorides in the water cause damage to gills and other parts of hermit crab anatomy and may cause them to die slowly and without obvious reason. Safe, non-fluoridated boiled, dechlorinated or bottled spring water should be used for everything coming in any contact with these animals, including substrate. Untreated tap water should not be used for hermit crabs.
Finally, ordinary household chemicals that are used routinely for cleaning (i.e. bleach, pine, ammonia, stain removers, carpet cleaners, air fresheners), beauty (hairspray, nail polish, acetone, perfumes), pest control (mosquito spray, insecticides), or lawn control (fertilizers, weed killers) may contain chemicals or fumes which may be deadly or at least harmful to the hermit crabs. Their modified gills may not be able to tolerate the levels of aerosolized chemical fumes that our lungs can. Most of these chemicals mentioned above are also toxic to human beings, however, they are much more harmful for hermit crabs because of their smaller size and different anatomy. No chemical fumes should be allowed near the hermit crabs or their tank, or used to clean the hermit crab’s tank.
It may not be obvious that these elements are harming the animals and if they are slowly dying from chemical injury or being poisoned from exposures, owners may not necessarily know it or understand why the hermit crab has died prematurely. The best thing to do is to try to keep these exposures to absolute minimum or if possible eliminate them altogether.
Hermit crabs may not be able to visually determine the edge of their footing, and will often fall off of ledges and may promptly walk off of the edge of a table, desk or bed if they are taken out of the tank, especially when afraid and in unfamiliar surroundings. If they injure core parts of the body, they may not be able to recover. Even within a large tank, it is possible for a hermit crab to fall and injure itself if there aren’t items which it can grip securely with its claws. Hermit crabs should be monitored at all times when out of the tank, especially on any ledge, and the tank design should include an awareness of the risk of fall. It is often surprising, and people may underestimate, how well a hermit crab can climb, and that they may escape a tank if the lid is left open or unsecured and drop down to potentially become injured.
Although they breathe through special gills, hermit crabs have a set amount of time which they may remain submerged in water before they cannot survive. It has been described to be as long as 30 minutes. However remarkable this ability is, only the hermit crab knows exactly when it must exit the water in order to survive, so there must always be an escape route from the water. Some owners will only keep the water ponds shallow for this reason so there is no risk of drowning when unattended. However, there is evidence that hermit crabs need to submerge from time to time to clean their shells and replenish shell water. This poses an issue with determining water level if there is variation in the size of the crabs, larger crabs may not have needs adequately met by a too-shallow pool and smaller crabs at risk of drowning with a deeper pool. Experienced crab owners have proven escape mechanisms from their deeper pools, secured vines, mesh, rocks, branches, etc. If designing deeper pools and unsure whether the hermit crab can safely escape, consider a supervised short test.
Attack/ Injury caused by Other Animals -
Although literature reports hermit crab shells are apparently strong enough to withstand the bite force of most land predators, they may possibly be injured by family pets. If they are whacked around, or bitten, or injured, there is no guarantee they will survive. Luckily they have the amazing ability to regenerate lost limbs, however the same cannot be said for the core portions of the body. It is best to supervise all other animals at all times around the hermit crabs. Even the friendly cat who at first seems calm and curious, may decide hermit crabs make a better toy to bat around rather than to watch. Additionally, hermit crab handling should be supervised with children who may become afraid and suddenly drop or fling the animal or unknowingly place it into a dangerous situation.
Potentially more likely than the above scenarios, however, is that the hermit crabs may be injured by other hermit crabs which reside in the tank with them. They are normally social animals which prefer species company, however aggression can arise for several reasons – notably shell ownership, space and territory (crab hierarchy). These situations also occur in the wild, however, in the enclosed environment of the tank there may be conditions which force or propel negative interactions, and the victim would not be able to simply escape. Having adequate supply of basic items is crucial: abundant shells, sufficient and diverse food offerings, and providing adequate tank space requirements for each crab and the colony is very important, as well as designing multiple areas to hide under and climb on so that they are not always competing for the same location. Hermit crabs may possibly become aggressive towards each other if their needs are not being met, including enough proper shells, dietary and space needs, and some feel that cannibalism of molting crabs may be related to dietary insufficiency. Whether or not diet plays a role or this is simply a natural phenomenon, protection of molting crabs can be achieved by isolation to another tank, deep substrate (6 inches or deeper) , and if necessary, constructing firm dividers or barricades (i.e. plastic, soda bottles, ornaments, plexiglass) to make the molting crab unreachable, or at least very difficult to reach or to be detected by smell by the other crabs.
Environmental Harms -
Since the hermit crabs are taken from the wild and natural environment their bodies were designed to be in, and placed in the household, they are already at a survival disadvantage. Their natural environment has to be recreated as best as possible in order to try to give them a chance at long and comfortable survival. There should always be an awareness of their surrounding temperature and humidity whether they are inside or outside of the tank. They should be observed at all times out of the tank because they are small and can easily slip away and become lost in the unfavorable environment of the home or worse outdoors. Some hermit crab owners do not endorse taking them out of the tank at all, except to clean or in emergency situations, in order to avoid the animal stress of having to adapt to unfavorable conditions. Physical stress of unfavorable conditions in the pet store and the drastic change to favorable conditions once purchased is understood to be the cause of Post-Purchase Syndrome which causes death within 30 days after purchase.
Nonetheless, in addition to maintaining temperature and humidity, hermit crabs must also be protected against harmful elements in the tank such as excess moisture and flooding, bacterial and mold overgrowth and infestations (mites, ants, etc.). In the wild they do not remain in an enclosed stagnant area, the sun is continually baking the sand or forest floor, wind, and the continuous movement of animals clean or renew areas and keep certain conditions from developing in the wild which may develop in a tank. Even if an area becomes uninhabitable, the hermit crab can potentially avoid these unfavorable areas in the wild in order to preserve itself. They would not have the option in the tank. Hence, it is important to try to prevent the conditions above from developing when planning your tank care, cleaning and maintenance regimens. Keep the tank clean and check with good and reputable hermit crab care sources and support groups to help determine which regimens and materials will provide the best chance at avoiding these adverse outcomes.
No care regimen will completely replace nature, and there will be some dangers that may not be able to be prevented or avoided inside or outside of the tank. However, the more aware and vigilant hermit crab owners are about these potential dangers to their pets, the better they are able to protect them.
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