The coconut crab (Birgus latro) is the world's largest land-dwelling arthropod, an extraordinary creature that can weigh up to 4kg and span nearly a metre from leg to leg. These impressive crustaceans are renowned for their incredible strength, climbing abilities, and the remarkable behaviour that earned them their name – cracking open coconuts with their powerful claws. While they're not suitable for casual pet owners, dedicated keepers with the right setup can successfully maintain these fascinating animals.
Important Considerations Before You Begin
Coconut crabs are not your typical pet invertebrate. Before committing to their care, you should be aware of several key factors:
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Legality: Coconut crabs are protected in many regions due to declining wild populations. Check your local laws regarding ownership, if your are in the UK these are currently fully legal to buy, sell and own
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Lifespan: These crabs can live for 40–60 years in the wild, potentially longer in captivity. This is a serious long-term commitment.
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Size: Adults are enormous by invertebrate standards and require substantial space.
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Strength: Their claws can exert a force of over 3,000 newtons – stronger than most animal bites. They can cause serious injury if mishandled.
Housing Requirements
Enclosure Size
Coconut crabs need large enclosures that accommodate both their size and their need to climb. For a single adult, the absolute minimum is 120cm × 60cm × 90cm (height), though larger is always better. Custom-built wooden vivaria with sealed interiors or large modified wardrobes are popular choices among keepers.
The enclosure must be:
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Escape-proof: These crabs are surprisingly clever and incredibly strong. Reinforce all joints and use robust locks.
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Well-ventilated: Adequate airflow prevents stagnation whilst maintaining humidity.
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Sturdy: The enclosure must withstand climbing and the considerable weight of an adult crab.
Climbing Structures
In the wild, coconut crabs are excellent climbers, scaling palm trees with ease. Replicate this in captivity by providing:
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Thick, sturdy branches securely fixed in place (they must support the crab's weight)
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Cork bark panels mounted to walls
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Rope or netting for additional climbing surfaces
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Multiple levels and platforms at various heights
Ensure all climbing structures are stable – a fall from height could injure or kill your crab.
Substrate
Provide a deep substrate layer of at least 15–20cm to allow for burrowing behaviour. A mixture of:
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Organic, pesticide-free topsoil
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Coconut coir
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Play sand
This combination holds moisture well whilst allowing the crab to dig. Keep the substrate consistently moist but not waterlogged – it should hold its shape when squeezed but not drip water.
Hiding Spots
Coconut crabs are primarily nocturnal and appreciate dark hiding spots during the day. Provide:
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Large cork bark hides
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Hollow logs
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Custom-built wooden shelters
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Dense artificial foliage for cover
Temperature and Humidity
Temperature
Coconut crabs are tropical animals and require consistently warm temperatures:
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Daytime: 26–30°C
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Night-time: No lower than 22°C
Use ceramic heat emitters or heat panels rather than heat mats, as the crabs will burrow beneath substrate-level heating and could be burned. A thermostat is essential for maintaining stable temperatures.
Humidity
High humidity is critical for coconut crab health, as they breathe through modified gills called branchiostegal lungs. Maintain humidity between 70–85% at all times. Achieve this through:
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Regular misting (2–3 times daily if needed)
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A large water dish that increases ambient moisture
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Moisture-retaining substrate
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Restricting ventilation slightly (whilst still allowing airflow)
A digital hygrometer is essential for monitoring conditions. Prolonged low humidity can be fatal.
Water Requirements
Coconut crabs need access to both freshwater and saltwater:
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Freshwater: Provide a large, shallow dish of dechlorinated water for drinking and soaking
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Saltwater: A separate dish of marine-grade saltwater (mixed to a specific gravity of 1.022–1.025) is essential for gill health
Both dishes should be:
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Large enough for the crab to submerge if desired
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Shallow enough to prevent drowning (despite their aquatic relatives, coconut crabs can drown)
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Fitted with ramps or rough stones to allow easy exit
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Cleaned and refreshed every 2–3 days
Feeding
Coconut crabs are opportunistic omnivores with a varied diet in the wild. In captivity, offer a diverse range of foods:
Protein Sources
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Raw fish and shellfish
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Cooked chicken (unseasoned)
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Boiled eggs (with shell for calcium)
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Dead insects
Fruits and Vegetables
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Coconut (of course!) – both flesh and husk
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Banana
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Papaya and mango
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Sweet potato
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Leafy greens
Supplements
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Cuttlebone or calcium powder for shell health
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Occasional vitamin supplements dusted on food
Feed adult crabs every 2–3 days, offering a variety of foods. Remove uneaten food within 24 hours to prevent spoilage. These crabs have an excellent sense of smell and will often cache food around their enclosure – check hiding spots during cleaning.
Moulting
Like all crustaceans, coconut crabs must moult to grow. This is a vulnerable and energy-intensive process:
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Pre-moult signs: Reduced appetite, increased time spent hiding, dulling of shell colour
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During moult: The crab will burrow and remain hidden for several weeks (sometimes months for large adults)
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Post-moult: The new shell is soft and the crab is extremely vulnerable
Critical moulting care:
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Never disturb a moulting crab
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Ensure calcium sources are readily available
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Maintain optimal humidity (essential for successful moulting)
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Leave the shed exoskeleton – the crab will consume it for nutrients
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Do not handle until the new shell has fully hardened (several weeks)
Failed moults are a leading cause of death in captive coconut crabs, often due to inadequate humidity or calcium deficiency.
Handling
Coconut crabs should be handled as little as possible, and only when necessary. Their claws can cause serious injury – they're capable of snapping broomsticks and have been measured exerting crushing forces exceeding that of any other crustacean.
If handling is required:
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Approach slowly and calmly
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Support the crab's body from beneath
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Never grab the claws or legs
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Wear thick leather gloves as protection
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Keep handling sessions brief
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Never handle during or after moulting
Many keepers choose never to handle their coconut crabs directly, instead using gentle coaxing to move them when necessary.
Health Considerations
Signs of a Healthy Coconut Crab
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Active during evening and night hours
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Strong appetite
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Clear, bright eyes
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Intact shell without discolouration
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Normal movement and climbing behaviour
Common Issues
Shell rot: Appears as dark spots or soft patches on the exoskeleton. Often caused by bacterial infection from poor hygiene or injury. Improve enclosure cleanliness and consult an exotic vet.
Lethargy: Could indicate temperature issues, pre-moult behaviour, or illness. Check environmental conditions first.
Limb loss: Crabs can autotomise (drop) limbs when stressed or injured. Lost limbs will regenerate over successive moults, but investigate the cause.
Failed moult: Often fatal. Prevention through proper humidity and calcium provision is key.
Finding a vet experienced with coconut crabs can be challenging – research exotic animal specialists in your area before you need one.
Bioactive Setup Considerations
Many experienced keepers opt for a bioactive enclosure for their coconut crabs. A bioactive cleanup crew can help maintain enclosure hygiene by breaking down waste and uneaten food.
Adding springtails to the substrate helps control mould growth and processes organic waste. Hardy isopod species can also be introduced, though be aware that coconut crabs may eat them – this can actually provide an additional protein source whilst the isopods help maintain substrate health.
Species like Dairy Cow isopods or Powder Orange isopods are prolific breeders that can establish populations fast enough to survive some predation whilst still providing cleanup benefits. Porcellio species are particularly hardy and can tolerate the warm, humid conditions coconut crabs require.
Conclusion
Coconut crabs are extraordinary animals that offer a unique keeping experience for dedicated and well-prepared enthusiasts. Their impressive size, surprising intelligence, and fascinating behaviours make them captivating to observe. However, their demanding care requirements, potential danger, long lifespan, and conservation status mean they're only suitable for experienced keepers who can commit to decades of specialised care.
If you can provide the right environment and are prepared for the responsibility, a coconut crab can be one of the most rewarding invertebrates you'll ever keep.
For more information on invertebrate care, bioactive setups, and supplies, visit www.postpods.co.uk