The Coconut Crab, Birgus latro
This is the largest land invertebrate, and a formidable crab, with a leg span up to 75 cm. This species also appears to be rather delicate in captivity. In a paper on the subject, Robertson (1991) gives some recommendations on husbandry and points out many of the problems known for this animal.
This animal comes from the Indo-Pacific tropics and parts of the Japanese Ryu Kyu islands. It ranges from the Aldabras to the Solomon Islands, Guam, and Fiji. It is threatened by invasive animals, by humans as a food and medicinal source, and habitat destruction.
Husbandry: This species should probably be kept singly, as aggressiveness has been reported. A permanently moist sand substrate and a half clay pot (used as a hideaway) are recommended. The crabs will burrow into the sand. A large bowl of fresh water is necessary. High humidity is recommended. (These are not salt-water animals.) Robertson reported using an 11 hour light/13 hour dark schedule, with a 27-29°C daytime temp and 23-26°C nighttime temp.
Feeding: These crabs are omnivorous, and Robertson reported the acceptance of coconuts, dead mice, fruits, fish, and small crabs. Cuttlebone was provided as a calcium supplement.
Problems: Mites were cleaned off with a water sprayer to remove any chance of damaging the crab's respiratory system. Stress appears to be a big problem with these invertebrates, and much care should be taken to keep traffic low around their cages. Bacteria (Vibrio) is a known pathogen. Moulting can also be difficult for these animals.
Robertson, M. 1991. Husbandry and moulting behavior of the Robber or Coconut crab Birgus latro at London Zoo. International Zoo Yearbook 30: 60-67.