Many new owners are perplexed by why hermit crabs dig and submerge themselves into the sand. However, burrowing is among hermit crabs’ most natural behaviors.
Sometimes, burrowing is short-term, such as searching for food, taking a quick nap, light recreation, or looking for privacy from conspecifics for a while.
At other times, hermit crabs may bury themselves for days when feeling overwhelmed and anxious. If a hermit crab is about to molt, it could be 4-8 weeks before it resurfaces.
Average-sized hermit crabs need a minimum of 4 inches of sand to burrow comfortably, while larger hermit crabs need a deeper substrate, ideally 3-4 times their size.
If hermit crabs can’t burrow, expect them to grow distressed. Not giving them the ability to engage instinctually will adversely impact their sleep, temperature regulation, and ability to molt.
Why Does My Hermit Crab Burrow?
Here are the most common reasons why hermit crabs bury themselves:
1/ Enjoyment
If you’re wondering, “do hermit crabs dig for fun?” the answer is yes. Aside from climbing steep inclines, digging is among hermit crabs’ favorite activities.
Some hermit crabs seemingly dig holes for the sake of it. Once they’ve finished, the substrate will be smoothed over, and they’ll explore elsewhere.
Sand is popular because it’s easy to burrow into and replicates hermit crabs’ natural environment. The sand should be kept moist, although an 80% humidity level in the tank resolves this issue.
How Do Hermit Crabs Dig?
Hermit crabs have claws of disparate sizes. The larger claw (the cheliped) does most of the digging, as this appendage can move more sand in one fluid motion.
The hermit crab then uses its second, smaller claw for digging finesse. This claw can move small amounts of sand out so the hermit crab can climb into the hole or move the substrate.
The smaller claw covers the hermit crab with sand once it has finished burrowing. Once a hermit crab feels secure under the sand, it tucks the claws into the shell as a protective barrier.
How Deep Do Hermit Crabs Dig?
Most hermit crabs dig at least 3-4 inches under the substrate. A wild hermit crab may dig deeper, especially if it’s a very hot day and wants to regulate its temperature.
If a hermit crab is larger or has a prominent shell, it may dig deeper. For example, Caribbean hermit crabs (also known as purple pinchers) can reach a size of 2-6 inches.
2/ Foraging for Food
Hermit crabs need a varied diet. According to the Journal of Experimental Marine Biology and Ecology, hermit crabs always gravitate toward food they haven’t recently consumed.
If you give hermit crabs the same meal for 2 days in a row, they’ll likely not eat it. Instead, they may bury the food. Hermit crabs are scavengers, so they’ll traverse the coastlines seeking sustenance.
3/ Fear And Anxiety
Hermit crabs take a while to adapt to changes in their living situation and adjust to life in captivity. When introducing a new hermit crab to a tank, expect them to bury themselves for several days.
This isn’t necessarily a cause for concern, as there’s every chance the new hermit crab emerges from under the substrate at night (they’re nocturnal) when the home is quiet and feels safer.
Is A Hermit Crab Being Bullied?
While keeping a small colony of hermit crabs in a tank is advisable, you must do your utmost to ensure they get along. Sometimes disputes arise over territory, mating rights, or the best shells.
If a hermit crab raps on a shell with its claws, it’s challenging the occupant. Another hermit crab covets the shell and invites the owner to exchange or fight for the right to wear it.
Some hermit crabs accept the challenge and wrestle for the shell, while others respond with fear, remaining in their shells and burrowing underground.
If the aggressor is particularly bold, it may force the incumbent hermit crab out of the shell.
Check how different hermit crabs interact because they amuse themselves and settle disputes with tests of strength, like feeler wrestling and pushing contests.
These can unfold without intervention, as a civil resolution will usually be agreed upon. Behavior explains that most shell disputes are “a process of negotiation rather than aggression.”
4/ Privacy
Wild hermit crabs live in colonies of up 100 animals. They feel safer and more comfortable among their own kind, so keeping lots of hermit crabs in a large tank is recommended.
Even the most extroverted hermit crab still needs time alone. Sometimes, hermit crabs burrow and hide underground for solitude, so it isn’t necessarily sleeping.
A male that wishes to mate will rap on the shell of a female, asking her to emerge. If the female isn’t interested, she’ll remain in her shell and seek to avoid his unwelcome attention.
5/ Temperature Regulation
Wild hermit crabs live in scorching weather conditions, usually on beaches.
While shells offer protection from the sun’s UV rays, most hermit crabs spend their days burrowed under the sand to regulate their temperature.
Captive hermit crabs have a heat lamp because they can’t self-regulate their temperature. If hermit crabs get too hot in their tank, they may burrow for some temporary respite.
Hermit crabs also need humidity, so they may dig a hole to find moisture. Without sufficient humidity, land-based hermit crabs are unable to breathe and will perish.
6/ Sleep
Hermit crabs burrow and sleep for 6-8 hours under the substrate during daylight hours. So, avoid disturbing sleeping hermit crabs and wait for them to awaken naturally when it’s dark.
7/ Molting
All hermit crabs need to molt occasionally, which happens several times in the first year of life, then approximately every 18 months.
Molting is the process of shedding the exoskeleton and growing a replacement. Often, it’s accompanied by an increase in size and mass, especially in young hermit crabs.
It can take a hermit crab 4-8 weeks to complete a molt, where it’ll need complete privacy. The signs that a hermit crab is about to molt include the following:
- Skin color fading to gray.
- Eyes becoming glassy and dazed.
- Growing tired and showing less interest in playfulness or interaction.
- Eating and drinking more than usual to store fat and water.
As the hermit crab is devoid of an exoskeleton when molting, it feels particularly vulnerable. This is why molting hermit crabs burrow themselves to stay out of harm’s way.
Is My Hermit Crab Molting or Dead?
The hermit crab will be buried under the substrate for such a long time you might think it’s dead. However, you shouldn’t dig up a hermit crab to see if it’s still alive.
In an unwelcome irony, the shock of disturbing a molt could kill the hermit crab. Instead, open the tank and sniff the air. Dead hermit crabs have an unmistakable aroma of rotting fish.
Consider how other hermit crabs are behaving. As per Ecology and Evolution, hermit crabs are attracted to the pheromones of dead conspecifics, so they’ll check if a now-vacant shell is a suitable upgrade.
If a hermit crab is molting and not dead, its tankmates are likelier to leave it alone.
8/ Sickness
Hermit crabs can live for 20-30 years if well cared for, but they can grow unwell. If so, the hermit crab will seek a quiet place (usually by burrowing under the substrate) to recover.
Most health concerns revolve around an unsuitable environment. So, ensure the tank adheres to the 80/80 rule – a temperature of 80OF and a humidity level of 80%.
Check the skin, as this signifies it’s about to molt or something is amiss, like a mite infestation.
Hermit crabs can live long lives in captivity, but all living creatures eventually die. The hermit crab may become more withdrawn and isolate itself when the end draws near.
Do Hermit Crabs Bury Themselves to Die?
If the hermit crab believes it’ll soon die, it may bury itself and pass away privately. Some hermit crabs vacate their shells when dying so other conspecifics can use them.
We can’t confidently say whether hermit crabs have a sense of their own mortality.
Should I Dig Up My Hermit Crab?
Digging the hermit crab up violates its sense of security, so it shouldn’t be disturbed.
You can spot-clean the substrate in a hermit crab tank while they’re burrowed, but only remove the topmost layer. Wait for the hermit crabs to wake up and grow active before a deep clean.
If a hermit crab has died, you’ll have little choice but to dig it up. The habitat will start to smell and attract flies and bacteria if you don’t remove the corpse.
If this isn’t the case, leave the hermit crab buried for as long as it wishes to remain this way.
