Some hermit crabs live underwater, spending little time on dry land. Despite this, hermit crabs can’t swim. Marine hermit crabs live at the bottom of the ocean and keep ten feet on the ground.
Most pet hermit crabs are terrestrial, spending the majority of their time on land and only submerging in water to bathe or store drinking water in a shell. If submerged in deep water, they’ll drown.
Hermit crabs can’t swim because their legs don’t bend at the knees, making it impossible for them to propel themselves through the water.
Do Hermit Crabs Live in Water or on Land?
According to the Bulletin of Marine Science, marine hermit crabs dwell 450 meters from the shore under the ocean. Land hermit crabs live on the beach, moving into shallow water for a short time each day.
All hermit crabs spend at least some time in the water. Terrestrial hermit crabs rely on water to keep their gills damp, which enables them to breathe easily. This is why humidity should be close to 80%.
Do Hermit Crabs Breathe Air?
According to Arthropod Structure & Development, land hermit crabs have evolved to develop a branchiostegal lung. Oxygen is absorbed through the gills, and the lungs distribute this around the body.
The gills of a land hermit crab must be kept moist to enable breathing, which means that terrestrial hermit crabs periodically submerge themselves in water.
If the gills become too dry, they close up, leading to suffocation.
How Do Hermit Crabs Breathe Underwater?
Marine hermit crabs draw oxygen from the water, using this to breathe.
The oxygen is converted to carbon dioxide and expelled through the mouth. Aquatic hermit crabs sometimes blow brown bubbles when they inhale pure air on land.
Aquatic hermit crabs occasionally visit the surface to scavenge for food. They can’t live on land for long, so suffocation becomes a risk as their gills dry out.
Terrestrial hermit crabs don’t breathe underwater. Instead, when submerged, land-dwelling hermit crabs hold their breath. Terrestrial hermit crabs only spend a short time underwater before returning to the shore for oxygen.
Do Hermit Crabs Need Water to Swim in?
Whether hermit crabs live underwater or on land, they don’t swim.
Marine hermit crabs live at the bottom of the ocean in the wild, making their way onto dry land when the tide is low. Terrestrial hermit crabs remain in shallow water, negating the need to swim.
This means you never need to supply water deep enough for land-based hermit crabs; offer enough water for drinking and bathing, not swimming.
Do Hermit Crabs Know How to Swim?
We’ve established that hermit crabs don’t swim, but is this due to choice or inability? Can hermit crabs swim in the water if this is a necessity? Hermit crabs can’t swim due to the biology of their legs.
While hermit crabs have ten legs; two are chelipeds, and four legs are too short for propulsion through the water. Only the second and third pairs of legs are used for locomotion.
Hermit crabs’ legs bend forward and backward, enabling them to move in a straight line. Unfortunately, the legs don’t bend at the knees, so propulsion through deep or choppy water is impossible.
Can You Keep Hermit Crabs in Water?
Only aquatic hermit crabs can live permanently in water, so they must be housed in a heated indoor aquarium of saline water. You can’t keep hermit crabs outside in a pond or other body of water.
Terrestrial hermit crabs must live in a dry substrate, such as sand or soil.
While hermit crabs need access to saline and fresh water for drinking and bathing, their time in the water won’t be prolonged, so they won’t need space to swim. Hermit crabs prefer other activities, like climbing.
Do Hermit Crabs Drown in Water?
Marine hermit crabs are not at risk of drowning in water. These animals have the opposite problem; they will struggle for breath if they spend too much time on dry land as their gills begin to close.
Terrestrial hermit crabs will drown in water if left unattended for too long. As discussed, land-based hermit crabs don’t breathe underwater. A hermit crab can hold its breath for a while, sometimes as long as 30 minutes, but will eventually need to vacate the water.
Minimize the risk of drowning in a hermit crab enclosure by providing simple access in and out of water sources. Ramps or a plastic mesh climbing net are recommended.
Can You Submerge Hermit Crabs in Water?
The reasons hermit crabs immerse themselves in water include the following:
- Bathing and removing substrate or fecal waste from their skin.
- Moistening the gills to allow continued easy breathing.
- Filling the shell with a store of drinking water in readiness for molting.
- Cooling off in hot temperatures (ensure your enclosure is no warmer than 84OF.)
- Attempting to shed a parasitic infestation, most commonly mites.
All land-based hermit crabs need to spend time in the water occasionally. The safest way to accommodate this is by placing an appropriate water source in the habitat.
If you keep terrestrial and marine hermit crabs, you can occasionally submerge terrestrial hermit crabs in an aquarium for a limited time. This will provide the land-based hermit crabs with new terrain to explore, but limit this time underwater to 20 minutes.
As Behavioral Processes explain, unfamiliar noise, such as a water pump, can disorient hermit crabs.
How Long Can Hermit Crabs Stay Underwater?
A healthy adult hermit crab can hold its breath for at least 30 minutes and stay underwater this long without concern. Some may even hold their breath for up to an hour. Younger hermit crabs have a shorter tolerance for time spent underwater.
As a rule, avoid leaving a terrestrial hermit crab underwater for longer than 20 minutes. If your hermit crab has not returned to the surface after this period, consider removing it manually.
How to Keep Hermit Crabs Safe in Water
Water safety is an essential part of caring for pet hermit crabs. Rules that you must abide by include:
- Always keep the water at an appropriate temperature.
- Never use tap water, and don’t use table salt to create saline water.
- Ensure that terrestrial hermit crabs can access and exit the water using ramps.
- Monitor terrestrial hermit crabs when they enter the water, removing them by hand if they’re submerged for more than 20 minutes.
Terrestrial and aquatic hermit crabs are different species and must be treated and housed accordingly.
If your hermit crabs are land-dwellers, take precautions surrounding water. Hermit crabs can’t swim, and deep pools of water are a life-threatening hazard.