Hermit crabs are ectotherms, meaning they don’t generate body heat alone.
As tropical animals, hermit crabs are also used to high ambient temperatures. You must provide a comfortable temperature of 72–84OF for your pet hermit crabs, especially during the winter.
Insulate the tank, turn on the central heating, or place a portable radiator nearby. If necessary, add a heat lamp or under-tank heater and provide a deeper substrate.
Ensure you have a thermometer in the enclosure to monitor the temperatures. If the tank is too cold, add a heat source. Also, check for behaviors that suggest your hermit crabs are cold.
If your hermit crabs spend more time hiding under the substrate, huddle together on the surface, and show a lack of interest in movement and exercise, their body temperature is too low.
Do Hermit Crabs Need to be Kept Warm?
Hermit crabs are from warm weather climates. While wild hermit crabs will still experience a winter, this will likely differ considerably from living in captivity.
A Caribbean Hermit Crab from Barbados will still be used to average winter temperatures above 80OF. Even Florida, the one location in the United States with a native population of hermit crabs, rarely reaches uncomfortable winter temperatures.
Maintaining a safe and comfortable temperature is paramount if you wish to keep hermit crabs as pets. They’re not cut out for cool climates and will grow sick and die during winter if not kept warm.
What Temperature is Too Cold for Hermit Crabs?
Many owners subscribe to the so-called “80/80 rule” in a habitat with a temperature of 80OF and a humidity level of 80%. This will keep your hermit crabs warm, healthy, and active.
As hermit crabs are active at night while you’re asleep, this temperature may drop.
Most hermit crabs can still function contentedly at temperatures as low as 72OF. Any lower than this, your pets will be at immediate risk of growing stressed and unwell.
Don’t allow temperatures to approach the low 70s in a hermit crab enclosure.
Get a thermometer – you can find these in pet stores for as little as $15 – and ensure that a safe temperature is maintained, especially when it’s cold outside the tank.
How To Tell if A Hermit Crab is Cold
Aside from checking the thermometer in a hermit crab enclosure, there are three signs that hermit crabs are struggling to cope with cool temperatures:
Burrowing and Hiding
Winter is the time of year you should see more of your hermit crabs, as they usually sleep 6–8 hours daily and are naturally nocturnal.
Hermit crabs should become more active in the winter as the sun goes down earlier.
If your hermit crabs are reluctant to rise from under the substrate at dusk or spend prolonged time inside their shells while on the surface, this suggests they’re too cold.
Your pet hermit crabs are attempting to conserve what little heat they can by minimizing exposure.
Hermit crabs are social animals, and even though they like to claim territory for themselves, it’s common to find a colony of hermit crabs sleeping on top of each other. This will usually happen out of sight, beneath the substrate.
If your hermit crabs are huddling together on the surface, they’re almost certainly too cold.
Marine Behavior and Physiology explain how this is a survival instinct. The hermit crabs are attempting to share what little heat they can find.
Alas, this huddling is unlikely to be effective in captivity. Wild hermit crabs live in colonies that stretch well into triple figures, and even then, this isn’t always enough to keep all the animals alive.
Four or five hermit crabs in captivity will never generate enough heat.
Lack of Movement
The most dangerous warning sign that your hermit crabs are too cold is a general lethargy and lack of movement. Once awake, happy and healthy hermit crabs will look to explore their surroundings, interacting, climbing, and scavenging for food.
If your hermit crab is sitting on the substrate, declining to interact with its surroundings, it may be too cold to generate the energy required to move. This is not a sustainable way for your hermit crabs to live.
Animal Biology confirms that any hermit crab exposed to prolonged cool temperatures will eventually die. You’ll need to take action to increase the ambient temperature before it is too late.
What Is The Best Way to Keep Hermit Crabs Warm in Winter?
Having established that hermit crabs need a little help to keep warm in the winter, you need to assess how to achieve this. Do hermit crabs need a heat lamp, akin to reptiles, or can you keep them safe and comfortable without a direct heat source?
The most effective option is increasing the ambient temperature in a room.
Achieve this by turning on the central heating or the strategic placement of a portable radiator.
This will help your hermit crabs remain comfortable without intrusive, potentially hazardous direct heat. If you prefer not to use these heat sources, perhaps due to concerns over energy bills or fire hazards, there are other ways to keep hermit crabs warm during the winter.
Heat lamps are primarily designed for reptiles but can also be used for hermit crabs. Heat lamps are placed in a particular habitat corner, offering a light source in addition to increasing temperature.
Heat lamps create one hot basking spot and leave the rest of the habitat running according to ambient temperature. This will stop your hermit crabs from growing uncomfortably hot and reduces the risk of severing the eye stalks due to prolonged light exposure.
If you use a heat lamp for your hermit crabs, consider installing an incandescent white bulb with as low wattage as possible. 25 watts should be sufficient but check the thermometer once the heat lamp is up and running.
Unde-tank, heaters are most commonly associated with fish aquariums. These are placed outside the habitat so they do not leave trailing wires or cables for curious hermit crabs to cut.
The average temperature generated by an under-tank heater is around 85OF, which could be too hot at the bottom of a habitat. Hermit crabs like to burrow toward the base of their enclosure to sleep, and temperatures above 84OF can be uncomfortable.
A solution to this is to affix an under-tank heater to the side of a habitat. This may be a little less aesthetically pleasing, but hermit crabs can bask in a high-temperature spot like a heat lamp or move to slightly cooler climes for a while.
If you lack power points near a habitat or can’t apply direct heat sources for any other reason, you must learn how to keep hermit crabs warm without a heater. The most effective approach is to insulate a tank.
While your hermit crabs are sleeping, wrap their enclosure in blankets or towels. For the best results, pop these in a dryer for a few minutes, so they hold some residual heat.
These materials will apply warmer temperatures to a hermit crab enclosure and, more importantly, maintain that heat. This means your hermit crabs are likelier to wake up comfortable and active.
If we are cold during the winter, we’ll add an extra blanket onto the bed or wear an additional layer. Placing more substrate in a hermit crab enclosure can provide a similar service. Instead of the usual six inches, increase this to nine or more.
As per Ecology, wild hermit crabs burrow further and further under the substrate when cold to protect themselves from the elements. More substrate makes this approach possible and ensures each hermit crab will retain its territory.
Consider changing the substrate used in an enclosure if this is your approach. Look for creature soil in an exotic pet store. You can use dirt as a hermit crab substrate; creature soil will trap humidity, increasing the temperature.
The only downside to creature soil is that it will generate moss, which may attract insects to a hermit crab enclosure during winter – including mites. You’ll need to be particularly alert to any cleaning needs.
Spraying Warm Water
Another small but effective change you can make is misting a habitat with warm water rather than cold. This will increase the humidity in the air, making hermit crabs a little warmer.
Don’t spray water straight onto your hermit crabs or heat their bathing water. Just boil a kettle and let it cool to lukewarm temperatures, then apply to a spray bottle and mist as normal.
Even though the water is boiled, it must still be purified or bottled – boiled tap water remains lethal.
Can You Use a Heating Pad for Hermit Crabs?
Heating pads are flat surfaces that generate higher temperatures. In theory, these could be placed on the floor of a hermit crab habitat to increase temperature.
Avoid heating pads, as they create too much intense heat in one location.
As heating pads run as hot as 85OF, your hermit crabs will quickly grow uncomfortable with the temperature. They also risk burning their feet, legs, and unprotected underbellies.
The same risk applies to hot rocks. These are decorations popular in reptile cages that provide a direct heat source. The same hazards apply to heat pads. As hermit crabs love to climb over rocks, you risk causing severe burns and significant injury.
If you want to provide a small, intense heat source, consider tossing hand warmers into a tank. These items, designed for humans to be worn under gloves, will release a short, manageable heat. Increasing the ambient temperature remains the safest approach.
Never leave your hermit crabs to battle the cold during the winter, as they’re not accustomed to temperatures below 72OF.