Hermit Crab

Hermit Crab

Latin Name Coenobita spp. Order: Decapoda Family:

Note relevant information about latin name, close relatives, etc.

Overview

They are a nice way to be able to draw correlations to ocean invertebrates, since we don’t have any fish or other ocean or purely aquatic species in our collection. Easy to handle and not hard to care for, either, of course. Not every kid has seen them, and they are fun for students to look at- especially those who have never been to the beach, and they differ enough from tarantulas and cockroaches that we find them to be helpful in explaining invertebrate characteristics- particularly to our younger students. They are a great opportunity to educate about proper care since the beachside novelty stores where you get the crabs at the beach don’t tend to actually tell you what they need to survive. They have value especially to teach people not to buy them as a disposable pet.

Just make sure they are handled enough to be comfortable coming out, and not hiding in their shells every time they are presented.

SPECIAL NOTE: There are sustainability concerns with this species – see the acquisition section below for more detail.

Natural History Information

Range and Habitat

Many different species of land hermit crabs live in tropical areas of the Indo-Pacific region, the western Atlantic and the western Caribbean.

Coenobita clypeatus is a tropical land hermit crab that lives throughout the Caribbean and as far north as Florida and Bermuda

Land hermit crabs live close to the shoreline and must have access to both land and water. They use pools and crevices of sea water to wet their gills and the interiors of their shells, and they reproduce and spend their early stages in water. Other hermit crab species are entirely aquatic. [1]

Hermit crabs spend most of their time in the mangrove and coastal forests, but is known to travel to high sand hills near the shore[2]

Longevity

20-30 years in the wild; with proper care, they can live that long under human care, too.

Ecosystem Role

Scavengers- they forage for detritus or carrion.

Husbandry Information

Housing Requirements

The bare minimum tank (or “crabitat”) size is 10 gallons for two small crabs, but 20 gallons is recommended. As they grow, you’ll need to keep upgrading. A good starter size for medium crabs is about 30 gallons.

Life Cycle Natural History Relevant Information

  • If the humidity drops and the air is dry, your land hermit crab will have difficulty in breathing through their modified gills.

Temperature, Humidity, Light Cycles

  • Temperature: Hermit crabs need a temperature gradient and relatively high levels of humidity to thrive. Temps should be 80 degrees F and never drop below 75
  • Humidity should never drop below 70% and should hover around 75-80%
  • 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 (UVB 5.0 bulb or LED bulb).
    • 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.

Substrate:

This species is usually housed in aquariums with sand substrate. Substrate needs to be deep enough to facilitate molting.

  • Suitable substrate – sand, coconut fiber, or a mixture of both (NO gravel). The bedding should be moist but not drippy and about 6 inches deep for medium crabs. Hermit crabs burrow into their bedding to molt, and the tunnels they make should be able to hold up on their own without caving in. It’s best to use playsand from the hardware store.
  • 5 parts play sand and 1 part eco earth- The consistency should be so that you could easily make a sand castle.
    • Use a brackish water to expand the eco earth bricks. This will help reduce the chance of mold. The eco earth should be DRY when mixed into the sand so you don’t end up with water logged substrate at the beginning. You can always add water once the environment is stable (wait 48 hours), if needed. In many cases it is not needed.
  • Orchid Bark (coco bark) is also used with success.

Social Housing/Colony Management

  • Hermit crabs are extremely social, foraging and traveling in groups.
  • While C. clypeatus is extremely social the species is known to be aggressive towards other hermit crabs in their group to steal better fitting shells.C. clypeatus is also cannibalistic and will eat vulnerable molting crabs.

Other General Housing Requirements or Management information

  • Water (water dishes, their bedding, their misting sprays) must be treated with a dechlorinator that removes harmful chlorine and chloramines, which can kill crabs, or allow water to age for minimum of 24 hours.
    • Hermit crabs need access to salt water along with fresh drinking water. Prepare two dishes, one with de-chlorinated tap water and one with de-chlorinated water with added marine aquarium salt (NOT table salt – this is poisonous to them).
    • Dishes should be deep enough for crabs to submerge their shells but not too deep that they cannot get out. If unsure, put some rocks, marbles, or other objects to help them in and out of the dishes.
    • Pueblo Zoo: A small dish of RO water and a dish of salt water are kept in the tank with them. They are also soaked in salt water 1-2 times a week.
  • Moss Moss is an excellent way to create and maintain humidity in their tank. Hermit crabs will seem to enjoy a big pile of moss to hide under and munch on.

Diet Requirements

Diet in the Wild

  • A crab may eat its molted shell, possibly for its calcium, vitamins and minerals.

Diet under human care

  • Hermit crabs should receive a variety of fruits, veggies, grains, nuts, seeds, etc.
    • Pueblo Zoo: We give them a tablespoon of shredded fruits and veggies every other day.
  • Hermit crabs should receive a variety of fruits & veggies (romaine, apple, sweet potato, cucumber, pear, etc.), grains, seeds/nuts (sunflower, pine nuts), etc.
  • They will eat proteins, which can be provided in the form of goldfish flakes, hermit crab pellets, turtle pellets, dried mealworms. Many facilities report using tortoise chow as well.
  • Check out the diet section of the Crabstreet Journal for a variety of crab diet recipes.

Veterinary Concerns

Enrichment & Training

Enrichment

Behavioral Relevant Information

  • Hermit crabs are always on the lookout for new shells to accommodate their growing bodies and will frequently change shells.
  • They are great climbers, often climbing trees in their natural habitats.
  • They are obligate scavengers, and forage in communities/socially. They are nocturnal foragers and may appreciate several feeding locations.

Environmental Enrichment

  • Plastic Plants and Vines
    • There are many types of plastic or fabric plants and vines which can provide enriching habitat features, as the crabs will 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.
  • Leaf litter (pesticide free) from known safe trees can be added on top but should not be mixed in.
  • Opportunities to climb.
  • Moss: Sphagnum, frog moss, beaked moss, and other. See list from the “Crabstreet Journal” for list of “safe” mosses to use for hermit crab environments

Behavioral Enrichment

  • Provide extra shells for crabs to switch between. Most facilities relay that they only provide natural (not painted or decorated) shells for their crabs.
    • Pueblo Zoo: We have 4 crabs and there are probably about 12 different shells in the tank with them at all times so they have plenty of options to choose from when they are ready to ‘move’.
  • Climbing Opportunities: climbing structure, cargo net, and shower caddies in upper corners to allow for higher perching.
  • Hermit crab treadmill

Schedule

Other Enrichment Resources

Training

Behaviors Trained

Reinforcers used & schedule of reinforcement

Other

Colony or Breeding Management

  • When housing multiple individuals together, a simple way to keep track of the colony individuals is to take photos of each in their shells. Then keep track of which shells become vacated and document the move. This works well for smaller colonies.

Individual Identification

  • Individuals are identifiable based on the shell they wear. However, because they can change shells, tracking these changes becomes more important for management.
  • What species of hermit crab do you have? Explore hermit crab species here.

Programmatic Information

Messaging Themes

  • Pets: Educate about proper care since the beachside novelty stores where you get the crabs at the beach don’t tend to actually tell you what they need to survive.
  • Loveland Living Planet Aquarium: We have Caribbean Hermit Crabs in our Ambassador Animal Collection. They are primarily used in our “Tides Field Trip” where students learn about biotic and abiotic factors in tides. In my opinion they are valuable ambassadors because there are so many conservation and educational messages about them you can share with guests.
  • Some ocean-side zoos have seen it as part of their educational mission to have their rescued former pet hermit crabs serve as ambassadors and teach this story, believing in their ability to change a lot of people’s thinking by sharing the hermit crabs’ stories and hopefully saved some hermit crabs from a short life as a “living beach souvenier.”

Threats and Conservation Status

  • There are significant conservation concerns with hermit crabs, especially pertaining to sustainable harvesting.
  • Philadelphia Zoo: We put hermit crabs in the “black category” for our pet wallet card, which meant never have them as a pet as they are not bred in captivity anywhere so they are all harvested from the wild. Compounding the issue is that they are harder to take care of than most people realize so they often do not live nearly as long as they can in the wild. They can make it over 20 years in the wild, and most in captivity do not live nearly that long which means we are not doing something right for them. Here is the link to the Pets Card
    • I am not sure if that has changed in recent years but I know a handful of people were trying to breed them. But because the require tides to reproduce it is very difficult to replicate.

Interesting Natural History Information

  • Land hermit crabs live close to the shoreline and must have access to both land and water. They are popular pets but do not breed in human care. Consequently, the pet trade harvests them from the wild, which is unsustainable.[National Zoo]

Did you know…

  • Hermit crab species come in a range of sizes, from a fraction of an inch to nearly the size of a coconut. [National Zoo]

Handling & Presentation Tips

  • Shedd Aquarium: They are pretty good with being taken out for a program with some desensitization. They are curious and like to explore their environment, so we will display them in a shallow container with sand and habitat.

Use Guidelines

  • Shedd Aquarium: Overall, the frequency of their use varies greatly depending on the time of year.

Public Contact and Interaction Guidelines

  • Shedd Aquarium: We don’t allow guests to pick them up. We can always take out an extra shell for guests to feel. Overall, the frequency of their use varies greatly depending on the time of year.
  • Loveland Living Planet Aquarium: guests are not able to touch our hermit crabs. We encourage educators to bring shell bio facts to provide something safe for touching. By limiting the touching and handling of the crabs, we have found no issues with stress.

Transportation Tips

Crating Techniques

Temperature Guidelines

  • What temperature ranges can this animal be used outdoors? Any restrictions for travel that are temperature specific? How long can they be used at each temperature?

Acquisition Information

Although species can be purchased from scientific supply companies, pet shops and companies that provide other aquarium livestock, please keep in mind that hermit crabs are unsustainably collected from the wild. One organization is working on captive propagation but it is complex and may be a while before captive bred hermit crabs are available. For this reason, each institution should decide on their comfort with participating in a currently unregulated trade that is reducing the populations of wild hermit crabs.

Look for specialty/exotic rescues such as:

Resources

Contributors and Citations

  • List here what facilities have contributed to this species page.

Comments from the Rating System

  • Pueblo Zoo: They are easy to care for, fun for students to look at- especially those who have never been to the beach (we have many since we are landlocked), and they differ enough from our tarantulas and cockroaches that we find them to be helpful in explaining invertebrate characteristics- particularly to our younger students. We give a fair amount of invertebrate-related presentations, so they are handled regularly and peek out of their shells during the classes.

Top Photo Credit:

credit the “header” photo of the species