Last Updated on October 22, 2023 by Joanne Harper
Hermit crabs are at the bottom of the food chain, hiding whenever real or perceived threats exist. They conceal themselves when unsettled or afraid, emerging when they feel safe.
They’re nocturnal animals, spending most of the day under the substrate. There won’t be much (if any) activity during the day. At sunset, hermit crabs awaken and become active, foraging for food.
Is your pet new? Post-purchase stress (PPS) causes new pet hermit crabs to hide for days. Being taken from their colony, transported miles, and adjusting to their captive life can be overwhelming.
Hermit crabs hide before shedding their exoskeleton. Small hermit crabs will stay burrowed for 2 to 3 weeks, and large hermit crabs may stay burrowed for several months.
Other explanations include temperature, humidity, predatory pets, noise disturbances, and hostility. For example, a rival wants the shell of another hermit crab, or a female doesn’t want to mate.
What Time Are Hermit Crabs Most Active?
Wild hermit crabs are most active at night for their safety and protection.
The sun’s ultraviolet rays can be harsh in the tropical climes that hermit crabs hail from, while many beaches that host them are much quieter after dark.
Hermit crabs spend their days hiding under the sand, sleeping during daylight hours. They’ll emerge once the sun goes down and scavenge for food.
This behavior will carry over into captivity, so ensure the hermit crabs have enough light and dark. Hermit crabs are nocturnal (active at night), so you’ll only see them after dark.
I Never See My Hermit Crabs Eat
If pet hermit crabs never seem to emerge, check back later. If the substrate is disturbed or the food is partially eaten, the hermit crabs are shy and prefer solitude.
If hermit crabs aren’t touching their food, something is amiss. If you have one hermit crab, it may be molting. If none of them are eating, this is because:
- You’re offering the same foods as hermit crabs prefer variety. The Journal of Experimental Marine Biology and Ecology explains how hermit crabs dislike eating the same food twice in 24 hours.
- This food has been consumed in the past and caused distress. According to The Biological Bulletin, hermit crabs learn from negative experiences.
- They’re uncomfortable coming out to eat due to external stressors.
- You haven’t added enough saline (salt) water to stimulate a hermit crab’s sense of smell.
- The food doesn’t have a strong scent, as hermit crabs detect food with their antennae.
Once these issues are resolved, hermit crabs usually emerge from hiding to eat after sunset.
Why Is My Hermit Crab Hiding?
A hermit crab may remain under the sand, not active or moving. Alternatively, it’ll surface from the substrate but hide in its protective shell.
This is likely to happen for one or more of the following reasons:
Post-purchase stress (PPS) occurs because hermit crabs have been taken from their colony on the beach, transported across the country, and find themselves in an unfamiliar environment.
After bringing hermit crabs home, don’t expect to see them for a while. You may not see them because post-purchase stress claims the life of some hermit crabs that can’t adapt.
Those that survive will eventually find the confidence to explore their surroundings.
How Long Do Hermit Crabs Hide When New?
Some hermit crabs recover in days, while others take weeks to adjust to their new surroundings.
Expect hermit crab to hide under for 1-2 weeks before surfacing. The closer the conditions mirror a hermit crab’s natural environment, the sooner it’s likely to gain confidence and cease hiding.
If a hermit crab is molting, it’ll hide under the substrate, not resurfacing until the process concludes.
When a hermit crab molts, it sheds its existing exoskeleton and grows a larger and healthier replacement. This is a vulnerable time for a hermit crab, so it mustn’t be disturbed.
Hermit crabs know when a molt is impending, often filling their shell with water and stocking up on food. Depending on the hermit crab’s size, they may remain in hiding for weeks or months.
Hermit crabs must live in an environment that feels natural. A tank must offer the following:
- Temperature of around 80°F. If a hermit crab is too hot, it hides under the substrate. Conversely, a hermit crab will remain in its shell and cease moving if it’s too cold.
- A humidity level of 80% because they need humidity to keep their gills moist and breathe easily.
- Recreational activity for hermit crabs, especially climbing apparatus.
- An appropriate balance of light and dark for their circadian rhythms.
The wrong enclosure conditions will make hermit crabs feel uncomfortable.
Hermit crabs will remain in hiding if something in the environment causes stress.
Examples of external stressors for hermit crabs include:
- Excessive handling. Only pick up hermit crabs occasionally once they trust you.
- Other pets, like birds, are near the tank.
- Noises around the tank. Behavioral Ecology explains how noise can disorient hermit crabs.
Maintain a calm environment if you want the hermit crabs to feel happy and contented.
Hermit crabs usually get along, but they have a hierarchy, and disputes can arise. Captive hermit crabs have limited opportunities to escape aggression, so they may remain hidden.
Hiding will usually involve staying still. If you wonder, “Why does my hermit crab stay in its shell?” there’s every chance it’s avoiding conflict with a more dominant tank mate.
According to Marine and Freshwater Behavior and Physiology, hermit crabs recognize each others’ scent.
Hermit crabs can enter conflict over shells. If a hermit crab has a shell coveted by another, it may issue a challenge, often involving “feeler wrestling.”
The incumbent hermit crab may hide to avoid this challenge, especially if it fears losing its precious shell.
Don’t Want To Breed
Females hide to avoid mating advances from males. They enter heat for around 4 days at a time, releasing pheromones. If the female is disinterested in mating, she may hide from males.
Hermit crabs are social animals that like being part of a same-species colony.
Also, other pets may show an unhealthy interest in stalking hermit crabs (like cats and dogs) or invoke fear. For example, birds are common predators on the beaches where hermit crabs live.
Why do my hermit crabs hide all the time? If you have a new pet hermit crab, it’s likely due to PPS.
If you have a juvenile hermit crab, it’ll molt regularly because it’s growing. Without an exoskeleton, a hermit crab is more vulnerable to external threats, remaining hidden until the process ends.
Provide species-specific tank conditions and give the hermit crab time to adjust to its surroundings. If hermit crabs are bullying each other, consider temporarily moving them to an isolation tank.
Keep the tank clean, but avoid unnecessary handling because hermit crabs are fearful animals.