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Identifying and Addressing Aggression in Hermit Crabs

Originally written by Vanessa Pike-Russell

Behaviour in the Wild

Identifying and Addressing Aggression in Hermit Crabs

Identifying and Addressing Aggression in Hermit Crabs

Land hermit crabs are territorial animals, and as such they will often act aggressively towards one another to establish a ‘pecking’ order among their colony. Sometimes this can be in the form of ‘feeler’ or antennae fights, others in violent pushing or flicking fellow tank mates out of the way. Usually this is not serious enough to warrant intervention. However, some hermit crabs will act in a manner that is harmful to other hermit crabs, often trying to pull their hermie buddy out of a desired shell, or attacking eyes, antennae, claws, legs or abdomen.

If you witness behavior that may be harmful to one or more hermit crabs, it is important to separate them until the aggressor has settled down. Sometimes tank aggression can be a precursor to a molt, or the result of being picked on or bullied in the past. The most common form of aggression is where one crab tries to pull their tank-mate out of the security of the seashell.

Handling with Respect and Gentleness

Holding hermit crab

Gently holding a hermit crab

It shouldn’t be forgotten that hermit crabs are not toys, but living animals. It is important to pick them up gently, carefully and talking softly to them to let them know that they are safe is often a good idea. Use slow and gentle movements and always remember to carry them steadily. If you were placed on a palm and thought you were going to tumble off the edge, what would you do? A hermit crab doesn’t have hands with fingers, it has claws and legs. In order to save itself it will grip on with what it has available, so remember to help your buddy know he is safe from harm and put yourself in the place of the hermit crab at all times. A hermit crab treated with respect and gentleness will be gentle. A hermit crab that is handled roughly and with anger or haste will soon let you know that he can be just as crabby!

Autotomy

Hermit crab with gel limb

Hermit crab with gel limb

In the wild a hermit crab will “throw” a claw or leg if another hermit crab tries to pull them out of their shell. This is a responsive behaviour and their limbs are built in a way that they are able to “drop” or “throw” a limb easily so they may survive an attack. This is called Autotomy.

Normal Behaviour

Tumble Time

Gentle sitting on Jimmy

Gentle sitting on Jimmy

You may see your hermit crabs climb over the top of each other, or perhaps flick each other out of a prized spot or corner. This is natural behaviour, and doesn’t normally harm your hermit crabs. You may have watched puppies or kittens playing and vying for the best spot near Mummy dog, ‘rough-housing’ and play fighting. The flicking and tumbling another hermit crab out of the way is just in the nature of the territorial hermit crab and helps to establish ‘pecking order’ amongst hermit crabs.

Stridulation (Chirping or croaking)

Hermit Crab Chirping Croaking (click to play!)

I was doing some reading of my “Biology of the Land Crabs’ book today and came across a chapter on stridulation behaviour in land crabs. Of specific interest was a paragraph on Coenobita:

“Stridulation in conjunction with posturing is common in aggressive displays of Coenobita (Hazlett, 1966; S. Gilchrist, unpub). Clicking by rapping of appendages together and by tapping the shell are integral parts of aggressive encounters of C. clypeatus and C. compressus. When alarmed, Birgus latro briskly stamps the second peripods. At other times, even when not apparently alarmed, this crab produces continuous clicks (Grubb, 1971). This may be a proximity warning to con-specifics.”

[ Reference: page 130 from Biology of the Land Crabs. Edited by Warren W. Burggren and Brian R. McMahon. Published in 1998 by Cambridge University Press.]

I have other references which I will dig up (literally, its all in storage) and share. From personal experience my hermit crabs mainly chirp when there is another crab bullying them. Prime example was when I heard ‘rheet rheet rheet’ and went over to the tank, saw one crab over the top of another one and trying to pull the poor crab out of its shell! I’d be making a lot of noise too! Some crabs have chirped or croaked when being picked up, but very rarely. It reminds me of a car alarm – sometimes its a false alarm, other times it means something is wrong.

Antennae Fencing

Antennae war

Antennae war

Another thing that hermit crabs like to do is to go up to each other and have a hermie ‘antennae/feeler wiggling and touching’ encounter. You might see the antennae moving quickly, and brushing against the antennae of the other hermit crab. This may take a few minutes to die down, and either crab lose interest. Sometimes it is almost as if they are talking in code, giving signals to each other. As long as they are not hurting each other, it is often best to let them interact and develop their social skills with other land hermit crabs.

Cheliped Clashes

Sometimes they may even brush cheliped, grasping claw, against each other. IF this progresses into an entirely aggressive act, such as trying to sever antennae, limbs, eye stalks or removing the other hermit crab from its shell, THEN it is time to ‘break it up’.

Mating Behaviors

Often the mating ritual will appear aggressive at first glance. However, if you observe the crabs you will see the male guarding his chosen female and fending off other males. He will never attempt to pull the female from the shell but he may rock her gently to coax her to come forward from her shell so that mating can occur. If she is resistant he will simply follow her around until she changes her mind. Females enter their ‘mating season’ after a molt so you will often find the males clamoring for a freshly molted female.

Some guarding behavior in C. brevimanus:

More guarding behavior in C. Clypeatus:

Shell-based Aggression

When one crab likes another’s shell, say Crab A likes Crab B’s shell, Crab A will go up to Crab B’s shell, knock its shell ( that of Crab A) against the other crab’s shell (Crab B), causing the crab in the desired shell (Crab B) to come out and have a look at what is going on. Now the first crab will try to pull the second crab out of its shell by a cheliped or other limb. The second crab will normally drop his cheliped(grasping claw) or leg/s and retreat inside his shell, using his remaining cheliped to protect himself. Preferring to loose a limb instead of loosing a shell.

Attempting to pull a hermit crab from its shell almost always results in the crab being torn in half (Ingle and Christiansen 2004), a testament to both its reliance upon its shelter and the strength to which its well adapted abdomen can hol on. The abdomen of all asymmetrical hermit crabs coils to the right and hence is better adapted to right-handed or dextril gastropod shells, though the less common left-handed shells are also utilised (Ruppert et al 2004). [1]

If there is a shell involved, it often helps if you place the attacker into a container with a number of suitable shells in different sizes, shapes and weights. It could well be that your hermit is crabby because his shell is too small. Imagine if you had to wear shoes two sizes small or large for you, and you were stuck in a glass tank and not able to go shopping to find a new one. What else could you do, but fight for the best shells with your tank mate. Remove the source of the aggression, and you will have relative peace and happiness in your crabarium.

Non violent shell theft video:

 

Perlatus shell fight by Melissa Nesgoda @hermitcrabs56304 on Instagram

Perlatus shell fight by Melissa Nesgoda @hermitcrabs56304 on Instagram

Perlatus shell fight by Melissa Nesgoda @hermitcrabs56304 on Instagram

Perlatus shell fight by Melissa Nesgoda @hermitcrabs56304 on Instagram

Perlatus shell fight by Melissa Nesgoda @hermitcrabs56304 on Instagram

Perlatus shell fight by Melissa Nesgoda @hermitcrabs56304 on Instagram

 

Deadly Behaviour

If you don’t remove the cause of the stress, you may just find that your overly stressed and crabby companion has ripped another hermit crab out of its shell, or viciously attacked it. If this happens, it is time to re-evaluate your crabitat and seashell collection, but first isolate the aggressive hermit crab and give it somewhere comfortable, equipped and containing an area it can retreat within darkness.

Somewhere Dark and Private

 

Hermies n Herps rock shelter

Hermies n Herps rock shelter

It is important that you have several spots within your tank for your hermit crabs to retreat within to escape the stress of life in captivity, mostly in partial darkness or protection from other hermit crabs. The most popular forms of tank decorations that meet this need are the Rock Caves, Coconut Huts, Hideout Dens, Terracotta (clean) flower pots, and more. Just like reptiles and many other animals, hermit crabs will be significantly less stressed if they believe they are protected from predators and allowed some cover of darkness.

Some Strategies

Over the past seven years I have had a handful of hermit crabs that were dangerously aggressive to their tank mates, and each time the best remedy was:

Terrarium

Terrarium

1. isolation
2. dark and private, quiet
3. access to more seashells, trade old shells for new shells, boil old shells and offer again
4. re-assess what you are feeding, is there enough protein in the diet?
5. observing the hermit crab on supervised visits to the crabarium

 

Larger Crabitats = More Space + Less Stress

If you are still having problems then it may help if you separate the crabs into two tanks, or upsize to a larger tank if needed, with a barrier. Most of the time people use a 10 Gallon or 20 Gallon LONG tank, which has very limited surface area. If you buy a larger tank, perhaps get one custom made. It is often cheaper due to the thinner base — no need to have the thickness due to heaviness of water in fish tanks. If you can’t afford this, it might help if you exercise your hermit crabs in a large, clean storage tub or other plastic container for a few hours a day (weather permitting).

Photo Credits: Travis Wease, Vanessa Pike Russell, Stacy Griffith, Michelle Stephens, Melissa Nesgoda

References:

  1. Dardanus megistos by Storm Martin 2012

Hermit Crab Essentials Shopping Checklist

Originally written by Vanessa Pike-Russell

hermit crab shopping list

Download this shopping list at the bottom of the article

Hermit crabs are advertised as cheap and easy to maintain, which is not necessarily true. To keep your hermit crabs happy and healthy, you will need to provide a lot more than food and water.

The following is a list of the essential items your pet hermit crabs will need:

Essential items for optimum land hermit crab care

Glass tank with lid:

A glass tank is preferred over plastic tanks, which will scratch and will not be able to hold the humidity within the ventilated lids. Plastic tanks are not large enough to provide the necessary space. A glass lid on a glass tank helps keep the temperature and humidity within hermit crab’s habitat, allowing for a slight gap for airflow. This airflow of fresh air into the humid environment will help to cut down on mould and bacteria, which can cause illness and even death among hermit crabs, often detected by a musty or ammonia odor.

Substrate:

Substrate is what we call the material that lines the bottom of the tank, and creates the ‘beach’ within your crabitat. The most popular substrates being: sanitized beach sand; silica dust-free play sand mixed with coco fiber bedding sold in compressed bricks. You will need enough of a depth to cover your largest Land Hermit Crab to three times it’s height. A minimum of 6 inches is recommended. A jumbo hermit crab needs at least 12 inches of substrate. Deep, moist substrate is essential for successful molting.

Under Tank Heater:

An Under Tank Heater or U.T.H. is a heat pad made especially for small animals and reptiles. An U.T.H. is used to keep the hermit crabs warm by gently warming the objects in the tank. You may need a thermostat to regulate the warmth of the tank if the temperature rises above 82F. Despite the name the heat pad is not placed UNDER the tank for hermit crabs. The heat pad is placed on the back wall of the tank typically.

Overhead light:

Hermit crabs require normal 12 hour cycles of day light and darkness at all times. Hermit crabs also may benefit from a UVB bulb. You can use a UVB or LED bulb to provide day light. You can use a red or blue LED for nighttime viewing but the crabs don’t require light at night.  For inexperienced pet owners we do not recommend using a heat lamp or emitter in place of a heat pad, it is challenging to control the environment with these products.

Dishes:

You will need at least three dishes: a fresh water pool, ocean water pond, and a food dish, non metallic. Pools should be deep enough for your crabs to submerge in.

Food:

Feeding commercial foods is not recommended. The only exceptions are foods that are free of chemicals. Land hermit crabs are omnivorous scavengers so they can eat a wide variety of foods. All foods should be free of chemicals and table salt. Check our list of safe and unsafe foods for hermit crabs and our Going Natural Beginners List for ideas on what you can feed to your hermit crabs.

 

Thermometer:

A thermometer is used to observe the temperature inside the tank. Thermometers come in three main types: the adhesive fish tank style, based on a sticker that changes colour as the temperature at the glass raises; the circular reptile-type thermometers which are based on a coil which contracts or expands; a digital gauge which uses a probe and allows you to measure the temperature at more than one location. If you can find traditional laboratory thermometers those can be used also. A combination wireless gauge is a simple solution.

For more on substrate temperatures visit: Substrate temperature V air temperature

Hygrometer:

A hygrometer is used to observe the humidity inside the tank. Just as with temperature, humidity is very important. If the humidity drops and the air is dry, your land hermit crab will have difficulty in breathing through their modified gills. Humidity should be near 80% relative humidity.

This wireless combo unit is a great option for you tank:

How to Calibrate Your Hygrometer

Water Ager/Conditioner:

Water Ager or Conditioners are very important if the quality of water is not suitable for use with fish in an aquarium and most tap water is not. It is important to removes harmful substances from tap water such as chlorine, chloramines and heavy metals, which can make hermit crabs ill. Chloramines cannot be removed by leaving the water sitting out for 24 hours as previously suggested.

Ocean Salt:

A sea water solution is recommended for the “Ocean Water” pool within your tank. Iodized salt, or table salt, should never be used for the ocean water pond. You should use a salt mix intended for salt water aquariums and mix according to package directions for fish. Fresh water salt is not the same and does not meet the needs of land hermit crabs.

For more on salt visit: The Importance of the Right Kind of Salt
For help on mixing ocean water visit: Mixing Ocean Water

Extras – Optional extras

Moss
Moss is an excellent way to create and maintain humidity in your tank. Your hermit crabs will love a big pile of moss to hide under and munch on. Check out our list of Safe and Unsafe Moss for Hermit Crabs

 

Water Glass, Marbles or Glass Pebbles:

Great to use in deeper water dishes to enable crabs the traction they need to get in and out, plus acts as a decoration.

Plastic Canvas or Gutter Guard

Perfect for creating ramps in and out of your water pools so there is no risk of a hermit crab getting trapped in the pool with no way out.

Plastic Plants and Vines

There are many types of plastic or fabric plants and vines which can improve the look of your crabarium, as well as to add entertainment for the crabs as they climb over, hide under and travel among the greenery. It is a good idea to create some dark spots in the tank, but be careful that they can’t climb out!

Substrate enhancements

The basic substrate mix of play sand and coco fiber is sufficient but you want to create a more realistic environment you can add some additional items to the substrate. If you can mix these in at the time you are setting up your tank that is ideal. Once your crabs are down molting it’s difficult to add more items. You can add coco bark (often sold as Orchid Bark), crushed oyster shells and leaf litter (pesticide free) from known safe trees. You can check out list of safe and unsafe wood.

Shopping Checklist

Mandatory:

  • Glass Tank
  • Solid Lid
  • Substrate
  • Gauges
  • Dishes – 2 deep dishes for water, you can use scallop shells for food
  • Heat pad
  • Food
  • Ocean salt for making ocean water
  • Dechlorinator
  • Shells
  • Furniture (for climbing and hiding)

Optional:

  • UVB 5.0 bulb
  • LED light hood
  • Mister
  • Moss
  • Plastic canvas or gutter guard
  • Water glass, Marbles or Glass pebbles
  • Plastic Plants and Vines
  • Orchid Bark (coco bark) organic

Bathing your Land hermit Crab

Originally written by Vanessa Pike-Russell

It is important that your land hermit crabs are able to bathe themselves. Bathing allows your hermit crab to re-hydrate their gills, replenish shell water and adjust the water salinity as well as flush out feces and wash off the sticky juices and food stuffs which are present when you offer fresh fruit, seafood and raw foods.

Hermit Crabs urinate through their antennae, so any water spills during handling is shell water. Hermit Crabs have an anus located on the end of their abdomen, and have been observed to flick any wastes (droppings) out of their shells. These feces are often brown colored and look like small sausage or ball shapes which consist mainly of sand and undigested foodstuffs.

Violascens bathing by Stacy Spangler

Violascens bathing by Stacy Spangler

You should provide deep fresh and ocean water ponds that your hermit crabs can wade through and bathe themselves in a “hands off’ method. Both the fresh and ocean water should be treated with dechlorinator, one that removes ammonia. Chlorine will burn a hermit crab’s gills and kill them.

The water dish must be one that they can easily get in and out of, and perhaps has items such as marbles, sea glass, pebbles, piece of coral or other item that will aid in their safe departure from the water, lest they drown.

Bathing after purchase

I do not use the submersion method unless I believe there is a reason, such as decomposing foodstuffs (crabs sometimes hoard food in their shell) or mites. It is stressful for land hermit crabs to be forcibly submerged in water, so it should not be done unless there is a real need. Always use lukewarm de-chlorinated water and be very gentle when placing the crab upside down in the water. Newly purchased crabs can be visibly checked for mites and kept in isolation for observation and treatment if you don’t want to risk introducing the mites to your main tank.

Based on the original article written and Copyrighted by Vanessa Pike-Russell

Want another crabber’s approach to bathing?

Should we change our minds about bathing Hermit Crabs?

Pros and Cons of Bathing by All Things Crabby

Photo Credits:

Stacy Spangler of www.isopodconnection.tictail.com

Methods for heating your crabitat

Compilation of information by Vanessa Pike-Russell and Stacy Griffith

Ways to heat your crabitat - Photo by Amber Miner

Ways to heat your crabitat – Photo by Amber Miner

To keep your hermit crabs healthy and happy their environment should be kept in optimum temperature and humidity levels. If you are not able to keep the environment stable then your crabs will weaken and become stressed which will lead to death. Hermit crabs are ectothermic creatures and must have a warmish and cooler side to their substrate. If your temperature falls below 75F on a frequent basis you need a reliable and safe method for heating your crabitat. Whatever type of under tank heater or other heating method you use, it is STRONGLY recommended that you buy a temperature control device such as a thermostat or rheostat. See some examples at the bottom of this page.

 

Sources of heating suitable for crabariums/crabitats are:

  • Under tank heat mats/pads or strips – ideal solution
  • Overhead lights – acceptable but challenging to maintain
  • Ceramic heat emitter – acceptable but challenging to maintain

Note: Heat rocks are not considered safe for hermit crabs!

Here are some examples of suitable products you can use to heat your crabitat.

1. Under-tank heaters AKA heat pads

A heat pad is the ideal solution for properly heating your crabitat. They provide even, consistent heat round the clock and can be paired with a thermostat to maintain exact temperatures.There are many types of under-tank heaters used with reptiles but you need to make sure your crabs do not overheat. For this reason we do not mount the heat pad under the tank despite it’s name. Heat pads are sold in a variety of sizes based on your tank size but those guidelines are often misleading. The heat pad should cover approximately 3/4 of the tank’s longest wall and should be mounted on the exterior side of the glass above the substrate line.  The heat pad should keep the temperature stable between 75 (cool side) and 85 degrees (warmer side). Hermit crabs are cold blooded creatures and must have a warmish and cooler side to their substrate. To accomplish this you can place the heat pad all the way to either end or your tank. Your heat pad may need an exterior layer of insulation to help direct all the heat into the tank. Your local weather and home temperature will affect the efficiency of the heat pad so tweaks may be needed between seasons. See the bottom of this article for a link to insulating products.

UTHs can be used on plastic tanks however, plastic tanks are not recommended for use as permanent crabitat!!

We strongly recommend you use a heat pad coupled with a UVB bulb to maintain the needed 12 hour day/night cycle.

Heat Strips are manufactured in the same way as mats. They are made narrower and are generally used to heat small boxes and the cages used for housing juvenile snakes and some other species. The principles of use are the same as those for mats and the same precautions should be exercised. In small enclosures the heat build up can be very quick. The temperature should be adequately monitored and controlled with a thermostat.

Heat pad or mats are available in multiple sizes. The type sold at most pet stores typically more expensive and the adhesive does not last very long. The Ultratherm heatpads are a very nice quality at a lower price. These can easily be mounted with tape and additional insulation can be added if needed.

Ultratherm heat pad at Reptile Basics

Ultratherm at BeanFarm

2. Lights

We do not recommend heating exclusively with overhead lights. It is challenging to maintain the proper environment with lights only. Plan for a heat pad and later adding an overhead UVB bulb.  Use of a UVB bulb may extend the life of your hermit crab in captivity. The typical use is a 5.0 reptile bulb for most tanks. The bulb should be mounted inside, near the top of the tank with no glass or plastic barrier between the bulb and the hermit crabs. I you have a very tall tank or a vertical tank you may need a 10.0 bulb. These come in a variety of styles. It’s recommended to get a UVB sensor or meter that can measure the bulb output. Species such as C. perlatus (Strawberry) spend more time on the beach and would benefit from more UVB exposure than a forest dwelling species.  UVB bulbs also have an expiration date. Research the bulb and find out how often it needs to be replaced and then record the day it was installed.

If you are in a region where heat pads are not available you can use an overhead light or heat emitter.

Now let’s looks at light fixtures you can use.

Clamp lights

You will need to switch bulbs from day to moon glo or purchase two lamps (unless you are using a heat pad at night). These fixtures will also hold a ceramic heat emitter.

Zoo Med ReptiSun T5 HO High Output Terrarium Hood

Zoo Meds Reptisun T5 Hood

Zoo Meds Reptisun T5 Hood

This low profile hood comes in several sizes and can be mounted inside your tank. These links also include the bulb!

24 inch

30 inch

36 inch

48 inch

Zoo Med T5 HO Reptisun Terrarium Hood takes reptile lighting to the next level with greater energy efficiency and higher UVA, UVB AND full spectrum light output. It employs a rapid start electronic ballast that maximizes lamp performance. The T5 reptile light fixture also features a highly polished curved reflector that directs light down into the terrarium so your reptile receives the full benefits of T5 HO High Output linear fluorescent lamps. The result is stronger UVB and brighter light output than standard T8 fluorescent reptile lamps. Increased light and UV output

Multi fixture hoods – Available in a variety of lengths

Bi Light Fixture

Pack your reptile’s daytime and nighttime heating all under one hood with this handy light fixture. Reptile terrarium heating and lighting has never been easier. The Bi-Light 2 Reptile Hood Lighting Fixture features two single high-heat ceramic sockets on separate switches and separate power cords and accommodates two incandescent bulbs or one UVB bulb and one incandescent bulb.

Tri Light Incandescent Fixture

Tri Light

Tri Light

Note: These are more difficult to find now.

Designed exclusively for terrariums, the Tri-Light fixtures feature high-heat porcelain sockets built to withstand the intense heat that is emitted from high-wattage incandescent lamps. A single socket and a double socket on separate switches and cords hold three incandescent lamps up to 150 watts each. The lamps can be plugged into individual timers for both day and night cycling. Available in 30″ size.(6″L x 31″W x 4″H)
Tri Light Combo Fixture

A combination fluorescent and incandescent light fixture designed to maximize the benefits of both types of lamps.
This allows for the use of a UVB-emitting lamp along with incandescent full-spectrum daylight/heat lamps and/or incandescent nocturnal/heat lamps. The fixture contains special heat-resistant ceramic sockets for the incandescent lamps and is designed to direct light and heat down into the terrarium. With the combo-light, hobbyists can create an ideal lighting environment for their terrariums.

Ceramic Heat Emitter

A ceramic heat emitter can be used a stand alone heat source or in conjunction with other heat methods. No light is emitted. A 50 watt emitter is good for most crabitats. X-Large crabitats may need the 100 watt. Your emitter should be mounted at the top of your crabitat. This is an easy way to maintain a range of temperatures in the crabitat.

Thermostats and Rheostats

Should I use a Rheostat (dimmer) or a Thermostat?

Don’t forget the bulbs!
The wattage and type of bulb you need will vary by fixture and by the size of your crabitat. Day bulbs and night bulbs are needed to maintain a natural light cycle which is vital to successful molting.

The easiest way to control the needed cycle is with one of these handy timer powerstrips.


A home for your Hermit Crab

Originally written by Vanessa Pike-Russell-Updated by Stacy Griffith

NOTE: The tank or habitat of land hermit crabs is often referred to as a Crabarium, Crabitat or Crabitank. This is a pet name for a hermit crab’s home.

A proper hermit crab habitat

A proper hermit crab habitat

The best housing is a glass tank with securely fitting lid.
A glass tank with lid helps keep the needed humidity and temperature levels stable. You should allow a small gap between the tank sides and the lid if condensation begins to appear on the sides of your tank.Disadvantages:Glass tanks, unless second hand, are somewhat expensive but worth the extra expense. If you have a lid that doesn’t allow for a gap for air circulation you can get a build up of condensation on the walls, which can cause bacteria build-up within the tank and create unsavory conditions for your hermit crabs to live in.
A proper hermit crab habitat

A proper hermit crab habitat

The MINIMUM

A ten gallon (10G) glass tank with lid is the minimum recommended size and will house up 2 small hermit crabs. If you have hermit crabs larger than a grapefruit then you will definitely need to upgrade to a larger tank. Larger crabs need more area to dig and moult, and to de-stress.

A proper hermit crab habitat

A proper hermit crab habitat

Different shapes and sizes

There are different shapes and sizes of glass tanks. The most popular type are called ‘breeder’ tanks and they are more cube-shaped than the standard ‘tall’ fish tank and have more floor space.

A proper hermit crab habitat

A proper hermit crab habitat- custom made

Custom Made Tanks

If you want a crabarium that will be more hermie-friendly, why not save some cash and get a custom tank built. Land Hermit Crab tanks do not need to have a bottom made as thick as with fish tanks do since they are not filled with water. If you phone around the different pet stores and aquariums, there are some custom tank builders that you can get a quote from to build to your specifications.

A proper hermit crab habitat

A proper hermit crab habitat

A popular size of custom made tank is a 2ft by 2ft by 1.5ft tank. It looks much like a ‘cube’ in shape, and has a base of 4 square feet. You will find that it is much easier to fit everything inside the tank that is essential, and that hermit crabs will not need to do the ‘spider walk’ along the edges of the glass because there is more room. Most fish tanks are very long and tall because fish are able to make use of the vertical height.
A proper hermit crab habitat

A proper hermit crab habitat

If you cannot get a custom made tank, try making use of the extra vertical space by installing levels or fixing climbing items such as sanitised mangrove root trees, sanitised driftwood, coral trees, ZooMed’s Jungle Gym, or even more creative, a network of choya (or other sanitised wood logs) that hermit crabs can climb and hang upside down and move along the network.
NOT a proper hermit crab habitat

NOT a proper hermit crab habitat. Kritter Keepers are death boxes.

Glass is better than plastic

Despite what your pet store or crab cart will tell you, land hermit crabs do not fare well in the plastic tanks with vented lids. If you do have a plastic tank with vented lid, the first thing you will need to do is cover some of the vents. You can use saran wrap (cling wrap) or sticky tape for this purpose.

Photo Credit: Stacy Griffith, Michelle Stephens

Understanding Humidity in the Crabitat

Originally written by Vanessa Pike-Russell-Updated by Stacy Griffith

What is Humidity?

Humidity is a measure of the amount of water vapor in the air. It can be expressed in several ways.

“Specific humidity” is the mass of water vapor per unit mass of combined dry air and water vapor, generally expressed in grams per kilogram. The specific humidity of an air parcel does not change with temperature.

“Absolute humidity” is the density of water vapor, expressed as grams per cubic meter of air.

“Relative humidity” is discussed below. Related terms are “saturation,” which describes the condition where water vapor is at a maximum concentration for the air temperature (warm air can hold more moisture than cold);

“dew point temperature” the temperature at which saturation occurs if air is cooled at constant pressure without addition or removal of water vapor; and

“vapor pressure,” which in meteorology is that part of the total atmospheric pressure due to water vapor content.

Reference: Arctic Climatography and Meteorology

What is the Ideal Humidity Range?

Humidity should be between 50-60% for Actual and around 70-80% relative humidity.

How can I measure humidity within my Crabitat?

You will need to buy a humidity gauge, also known as a hygrometer.
There are many kinds, some of the more popular are shown below.

Why is my Hermit Crab so inactive?

C brevimanus

C brevimanus

Originally written by Vanessa Pike-Russell-Updated by Stacy Griffith

There are a few reasons your hermit crab may be less active than you expected.

  1. Natural instincts
  2. Incorrect temperature and/or humdity
  3. Crabitat does not provide an interesting, enriched habitat
  4. Pre- molt
  5. Impending death

Land Hermit crabs are primarily, but not exclusively, nocturnal creatures. That means that in the wild they sleep during the day and are active at night. This allows them to escape the drying heat of the sun as well as predators. They hide away in the leafy foliage or cool areas and are active once the sun has set and the moon is out, roaming about in groups of 100 or more in search of food. If a shadow passes over your hermit crab you will see the instinctual reaction of your hermit crab retreating within their shell for protection. Imagine the shadow of a bird passing overhead, wanting you for dinner , wouldn’t you would retreat into your shell to pretend to be just a shell? I would! Spending quiet time near the crabitat will help your hermit crabs get accustomed to your presence. Do your best to avoid throwing shadows over the tank, master the hermit crab belly crawl if necessary!

Another reason for inactivity is incorrect temperature and/or humidity in the crabitat. If the temperature falls below 72F, or the humidity within the crabitat is below 70% your crabs will stay hidden away and less active. It is important to keep a comfortable environment for your hermit crabs as the incorrect environment will slowly kill your hermit crabs.

Is your crabitat boring? One way to increase activity is to create an obstacle course within the tank, using cholla logs or driftwood, coral and/or rocks. Providing an enriching environment will encourage your hermit crabs to explore. They are curious beings and they love to climb.

If your hermit crab is inactive for a long period of time which follows the habit of spending a lot of time in the water dish, your crab may be preparing to molt. Pre molt symptoms vary from crab to crab. Some crabs get slow and cranky, others are busy, some load up on food, others increase their water intake.

The final cause could be impending death. This could be a result of incorrect habitat conditions, incorrect food (nearly all hermit crab food sold in retail stores is toxic) or PPS (post purchase stress).

Why is an ocean pond needed?

Originally written by Vanessa Pike-Russell-Updated by Stacy Griffith

All hermit crabs require some access to salt in their diet, no matter what species. The habitat of land hermit crab species differs from location to location, and they have adapted to the environment they live in.

Approximately 3.5%, or 35 parts per thousand solution is recommended for the “Ocean Water” pool within your tank. Typically mixing according to package directions is sufficient. If you are using distilled or spring water it may have varying amounts of salt already within the water, so take that into consideration.. It is important to note which type of water you use.Varying habitats of land hermit crab species. It may surprise you to know that the habitat of land hermit crabs is rather diverse. Some live in rainforest areas while others exist on coral atolls or inland areas. If you have many species within the same crabitat then you will notice that some will drink more sea or ocean water than others. It is important that you provide an ocean or sea salt water pond within your crabitat so that each crab can take what it needs and lead a happy and healthy life.

“Although there are relatively few species of Coenobita, individuals are numerous in tropical and subtropical maritime regions particularly supralittoral areas and small islands, although some penetrate further inland. Certain species are restricted to beaches (e.g. C. perlatus (H. Milne Edwards, 1837), C. scaevola (Forskal 1775), C. spinosus (H. Milne Edwards, 1837), C. cavipes (Stimpson, 1838) while several other species may penetrate long distances inland, e.g. C. clypeatus (Herbst, 1791) on Curacao, C. rubescens (Greeff) and C. brevimanus (Dana, 1852) in rainforest, C. compressus (H. Milne Edwards) (de Wilde; 1973; Burggren and McMahon, 1988). Coenobita rugosus (H. Milne Edwards, 1837) may live on the beach or penetrate inland in situations where fresh water is available (Yamaguchi, 1938; Vannini, 1976). stages.” Greenaway (2003 p. 13)

Beach-dwelling Land Hermit Crabs Some hermit crabs live on or close to beaches and would have access to seawater and a diet high in salt. In captivity they will need access to sea water. You will often find hermit crabs which have been denied sea salt water solutions spending a lot of time in the ocean water dish once you get them home.

“Certain species are restricted to beaches (e.g. C. perlatus (H. Milne Edwards, 1837), C. scaevola (Forskal 1775), C. spinosus (H. Milne Edwards, 1837), C. cavipes (Stimpson, 1838)… Beach-dwelling coenobitids drink seawater or extract it from damp sand and often immerse themselves to flush the shell.. ” Greenaway (2003 p. 13-16

Other land hermit crabs, despite living away from beach areas,  will drink the sea water from time to time or access salt through their diet. You may find your Caribbean (Purple Pincer aka C. clypeatus) hermit crabs drinking the sea water. While they may not have ready access to seawater in the wild they do drink it while in captivity, and there is often a link between excessive drinking of sea water and an impending moult.

“Coenobita spp. that live away from the beach do not usually have access to seawater and indeed these species prefer dilute water unless they are depleted of salt (de Wilde, 1973). ” Greenaway (2003 p. 16)

How to create ‘Ocean Water’ from Synthetic Sea Salt

If the package doesn’t give mixing directions you will be safe using this ratio: Mix eight tablespoons (1/2 cup) of Marine Salt to a Gallon (4 Litres) of dechlorinated water. This equates to roughly 2 tablespoon per Quart/Litre.

Once mixed, the solutions should be permitted to sit for 12-24 hours prior to serving to ensure the ocean crystals have dissolved. Make sure that you shake the solution if it has been left to stand thus to dissolve any undissolved salt crystals.

Quality brands which may be used include Instant Ocean, Instant Ocean Reef Crystals, CoralSea, Oceanic, Reef Crystals from Aquarium Systems, and Tropic Marin. Each brand should be mixed according to the instructions on the package.

For further information, and smaller quantity mixing directions, please see the Ocean Mixes page.

Instant Ocean

From the Aquarium Systems website:”Instant Ocean synthetic sea salt contains every necessary major, minor, and trace element and has no nitrates and no phosphates. It was developed through sophisticated biological and chemical testing, and every batch is analyzed to assure consistent high quality. Exceptional solubility, uniform particle size, and outstanding package value have made Instant Ocean salt the choice of aquarists for over 30 years. No other product outperforms Instant Ocean salt. Our guarantee of quality is supported by a history of proven usage. Instant Ocean is the world’s most popular brand of synthetic sea salt.” Add 1 1/4 tablespoons of Instant Ocean to a Litre of dechlorinated water

Tropic Marin

“Tropic Marin sea salt is manufactured from pharmaceutically pure salts and is based upon the most recent scientific analysis of the tropical oceans. It is free from synthetic additives and contains no nitrates, phosphates or silicates. Tropic Marin Sea Salt turns fresh water into salt water, which is practically indistinguishable from natural seawater.”Add 151 grams or four heaped teaspoons of Tropic Marin sea salt for 1 gallon of de-chlorinated water.


References:

Articles:

Greenaway, P. (2003)Terrestrial adaptations in the Anomura (Crustacea: Decapoda).
Memoirs of Museum Victoria 60(1): 13-26 (2003).

Websites:
Aquarium Systems:: Salts
http://www.aquariumsystems.com/salts.htm
Tropic Marin
http://www.tmc-ltd.co.uk/aquariumproducts/tropicmarinsalt.asp

Why do land hermit crabs drop limbs?

Lost Limbs

Hermit crab dropped leg

Hermit crab dropped leg

What is Autotomy?

Comes from the latin words autos for “self” and tomos for “cut

Autotomy can be described as self-cutting, Websters dictionary describes autotomy as a “reflex separation of a part (as an appendage) from the body: division of the body into two or more pieces.” Hermit Crabs can autotomize (drop) and regenerate (regrow) their limbs from juvenile to adult stages. The break occurs along a fracture plane located at the appendage’s base.

Why do land hermit crabs drop limbs?

The rate at which the limbs regenerate depends upon the molt cycle (Morgan, 1900; Zeleny, 1908; Bliss, 1960; Skinner 1962, 1985). During aggressive encounters, a crab will often choose to flee and autotomize (self-amputate) the limb being held so that they can escape. Other reasons why a land hermit crab may self-amputate is in response to stress, ill health, to reduce blood loss from a wound, or as a response to the presence of bacteria or pests. (Cooper, 98). There is a thin grove on each crab appendage close to where it joins the body. This is the fracture plane, along with an internal membrane. Separation occurs instantly through

Stress from fluctuating temperatures

Hermit crabs are stressed by changes in environmental factors, it is too hot or cold, humid or dry. Some times when hermit crabs lose limbs it is a sign of stress or ill health. It is important to keep your crabarium as close to the environment they are used to in the wild. That means recreating the tropics which as we know means warmth and moisture.

Aggression

There are cases where one hermit crab will act aggressively towards another hermit crab. It could be territorial or over a desired shell. In the wild a hermit crab will “throw” a claw or leg if another hermit crab tries to pull them out of their shell. This is a responsive behaviour and their limbs are built in a way that they are able to “drop” or “throw” a limb easily so they may survive an attack. This is called Autotomy.

When one crab likes another’s shell, say Crab A likes Crab B’s shell, Crab A will go up to Crab B’s shell, knock its shell ( that of Crab A) against the other crab’s shell (Crab B), causing the crab in the desired shell (Crab B) to come out and have a look at what is going on. Now the first crab will try to pull the second crab out of its shell by a cheliped or other limb. The second crab will normally drop his cheliped (grasping claw) or leg and retreat inside his shell, using his remaining cheliped to protect himself. Preferring to loose a limb instead
of losing a shell.

Illness from contaminated living conditions

There are many stores that do not meet the needs of the land hermit crabs they sell. If a tank is overcrowded, unclean and there lack of fresh water. It is important that you regularly clean the tank and remove any signs of contaminated foodstuffs or mouldy substrate.

Mite infestation

If your hermit crab tank has a mite infestation you will need to get rid of them ASAP! Visit the MITES page for more information.

Molting Complications

Another reason crabs lose a limb or a cheliped is when a crab moults and does not shed their entire exoskeleton in one piece, but instead section by section, over a number of days. Generally if they survive the moult they grow their limbs back again (regeneration) and can be happy and healthy.

Why doesn’t the crab bleed to death?

The crab does not lose blood because it instantly clots. A second membrane helps in closing the wound, creating a nub-like covering which develops into a limb bud.

What happens next? Can they regrow the lost limb?

Gel pincher regenerating Photo by Lamont Darren Medley

Gel pincer regenerating Photo by Lamont Darren Medley


Hermit crab gel limb - limb regeneration

Hermit crab gel limb – limb regeneration


A nub-like covering developing into a limb bud, which is at first transparent and slowly unfolds. After one or more moults the bud (or ‘gel limb’ as it has been described) soon regenerates to the way it looked before the limb loss and will return to full size after a few moults. Sometimes this can trigger a number of moults one after the other as the crab struggles to regenerate all limbs successfully. Sensory neurons must grow and re-establish the appropriate connections with the neural network of the ventral nerve cord if the new limb is to exhibit its original function (Cooper, 98).


Rugosus gel limb

Rugosus gel limb


C. compressus surface molt. Top most leg is a newly regenerated limb.

C. compressus surface molt. Top most leg is a newly regenerated limb Photo by Nichole Edwards.


COOPER98_fig1

COOPER98_fig1


COOPER98_fig1

COOPER98_fig1

(Fig. 1. and Fig. 2 from Cooper, 1998)

References:

Anatomy for Veterinary Technicians. Purdue University School of Veterinary Medicine
http://www.vet.purdue.edu/~lamarch/term.htm

Bergmann, M., Taylor, A.C. & Moore, P.G. 2001. Physiological stress in decapod crustaceans (Munida rugosa and Liocarcinus depurator) discarded in the Clyde Sea Norway lobster fishery. J Exp Mar Biol Ecol, 259: 215-229.

Cooper, R.L. (1998) DEVELOPMENT OF SENSORY PROCESSES DURING LIMB REGENERATION IN ADULT CRAYFISH. The Journal of Experimental Biology 201, 1745–1752 (1998)

MORGAN, T. H. (1900). Further experiments on regeneration of the appendages of the hermit crab. Anat. Anz. 17, 1–9.

William H. Amos (2003). Breaking Off. Hidden Worlds Back. Saturday February 1, 2003
URL: http://www.caledonianrecord.com/pages/hidden_worlds/story/521f67cc0

Misting your Hermit Crab

Misting Your Hermit Crab

Misting is commonly considered to be unnecessary and potentially stressful by most crabbers. If your tank humidity is at a recommended level and you offer fresh and salt water pools deep enough for your crabs to wade in, there is no benefit in regular misting. If you choose to take your hermit crab out of its tank for playtime or exercise, it is a good idea to mist the gills.