Land hermit crabs: fascinating wanderers between two worlds

In the warm coastal regions of Asia, Australia, North and South America and parts of Africa, hermit crabs have turned their backs on the sea and live on land. However, of the more than 1,100 species of hermit crabs distributed among 120 genera, only a scant 20 species, classified into two genera, have made this move. they are the land hermit crabs (Coenobita) and the closely related palm thief (Birgus latro), the largest land-dwelling invertebrate in the world. All other hermit crabs live in the sea. There are good reasons for this: first, hermit crab larvae can only develop in the sea, and second, hermit crabs, like all crabs, breathe through gills. The latter problem has been trickily solved by land hermit crabs, as will be read later. The other problem persists. The land hermit crabs still have to return to the sea to release their larvae. That is why these animals are always found relatively close to the coast, because such a small animal cannot crawl further than a few kilometers, even if this is only necessary once a year.

The palm thief, Birgus latro, is a land hermit crab and the largest land-dwelling invertebrate of all. Its care is reserved for specialists and zoos.

Most species turn up in the pet trade from time to time, often misidentified. In principle, this is not a problem, because all land hermit crabs are excellent terrarium animals, but the different species have quite different requirements for housing and care. Above all, the question of whether or not salt water needs to be provided is quite important. As mentioned at the beginning, land hermit crabs also breathe via gills. For this purpose, they dip specially shaped, brush-like legs into water and moisten the gill cavity located inside the body; because only if they are sufficiently moistened, gills can function. For some species, freshwater is sufficient to keep the gills functioning, but others need seawater to do so.

During the day, when the sun shines, all the hermits are in their hiding places
In the evening the animals come out. This is a beach terrarium for Coenobita perlatus

Because of the gill breathing, land hermit crabs are also mainly nocturnal, because then the humidity is higher. In terms of their activity times, they can be compared quite well with our Central European land snails, which can also be found during the day only in rainy weather. Land hermit crabs spend the day buried in moist soil. Therefore a minimum of 10 cm, better 15 cm high substrate in the terrarium is elementary important for a successful care of land hermit crabs. Land hermit crabs also need this for molting. Like all crustaceans, land hermit crabs need to molt in order to grow, as the crustacean shell cannot grow. Juveniles molt several times, adults usually only molt once a year. If the substrate is not deep enough and sufficiently moist (not wet!), molting problems will occur, which are usually fatal for the crayfish. The depth of the substrate is critical because only in complete darkness is the hormone needed for molting produced in sufficient quantity. Since the land hermit crabs need a larger snail shell after molting, one must always provide sufficient empty snail shells of suitable size in the terrarium.

Coenobita rugosus is a common and very suitable species.

Land hermit crabs cannot tolerate cold. Therefore, the terrarium temperature must always be above 18°C, preferably in the range of 20-26°C. Land hermit crabs are omnivores, so their diet does not cause any problems. A large handful of autumn leaves forms the food base in the terrarium and should always be available. Add to this fruit, vegetables, salads, fish food flakes, pellets, canned cat and dog food, small dead fish, etc. One should always give only so much of these kinds of food, as is eaten up over night completely. The exact amount of food must be determined by yourself, since the animals develop different appetites at different times of the year and depending on the moulting interval. Daily spray the terrarium with lukewarm water, preferably in the morning and evening. For the furnishing you can use gnarled roots, branches and stones, but be careful: the little rascals develop amazing powers! Stones must also rest on the terrarium floor, so that they cannot be burrowed under and possibly become a death trap. Every day, place a shallow bowl of fresh water and – for species that need it – a bowl of seawater in the terrarium.

Coenobita brevimanus is a forest species that can easily survive without seawater. Only for larval release this species must go to the coast.
Forest terrarium for Coenobita brevimanus

Basically, land hermit crabs are social animals that communicate with each other even by means of very quiet chirping sounds. Therefore you should keep them in a group, 5-6 animals are good, 10-15 are better. The sexes can only be distinguished when the animals change house; females can then be recognized by the additional legs on the abdomen, to which they attach the eggs and carry them around until hatching maturity. They then begin the migration to the sea – a perilous time when a great many females perish in the wild. When they reach their destination, many more females drown, because land hermit crabs can no longer live underwater. But each female that makes it releases hundreds of larvae that, after a few weeks in the plankton of the oceans, become miniature hermit crabs and go ashore. Even though, as with almost all wild animals, over 99% of the young born die early, in the case of land hermit crabs there are so many that in fact the number of empty snail shells available on the ocean shore is the limiting factor in how many land hermit crabs can transition to land life.

Now hurry up, or someone will snatch the house away!

Land hermit crabs are very beautiful, highly interesting terrarium animals. If you are seriously interested in their care and breeding, you cannot avoid the book “Land hermit crabs“, because it is the only book in the world in which all known species are considered and in which numerous tricks and tips that save from disappointment are presented in a practical and easy to understand way.

Frank Schäfer

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About the author Frank Schäfer

Biologist Frank Schäfer, born in 1964, has had a passion for keeping animals and plants since his earliest childhood. Right from the start his particular interest has been fishes, but he is also fascinated by reptiles, amphibians, invertebrates, small mammals, and birds, as well as a multitude of plants...

Since 1980 he has been a member of the Verein für Aquarien- und Terrarienkunde Hottonia e.V. (Hottonia Aquarium and Terrarium Society), where since 1982 he has also repeatedly been a member of the committee (Garden Curator, Editor of the society's journal, First Secretary); since 1982 a member of the Internationalen Gemeinschaft für Labyrinthfische (IGL, International Labyrinthfish Society) and since 1992 the European Anabantoid Club (EAC) as well. His first articles, on the maintenance and breeding of Puntius vittatus, Macropodus opercularis, Trionyx ferox, and Polypterus senegalus, appeared in the Hottonia-Post in 1981; his first major fish-collecting trip to the Tropics was in 1983, to Sumatra, resulting in numerous articles in the Hottonia-Post, the magazines Der Makropode and Das Aquarium; from then on regular publications in numerous aquarium magazines, both national and international. In addition for many years he has given several illustrated presentations annually at national and international conferences.

He studied biology in Darmstadt from 1984-1989, leading to a Diploma in Biology with examination papers in zoology, botany, ecology, and psychology. His thesis (under Professor. Ragnar Kinzelbach) was on the topic of the host specificity of the glochidia of Anodonta anatina.

He has made numerous fishing, collecting, and research trips to other European countries, Turkey, Zambia, and above all India; the focus of his research has been the freshwater ichthyofauna of the Ganges with the goal of a complete revision of the work of Francis Hamilton (1822): An account of the fishes found in the river Ganges and its branches. Edinburgh & London. He published the original scientific description of Oreichthys crenuchoides and, together with Ulrich Schliewen, that of Polypterus mokelembembe. He has made research visits to and worked for short periods in the zoological collections of London, Paris, Brussels, Tervuren, Vienna, Berlin, Frankfurt, and Munich.

From 1996 to the present he has been editor at Aqualog and scientist responsible for fish identification at Aquarium Glaser, Rodgau. During this period he has been author or co-author of more than 20 books and more than 400 major articles, not just at Aqualog but at practically all German-language publishers in the field, as well as occasionally in international publications. Since 2009 he has been responsible for the website and Newsletter at Aquarium Glaser, with 3-5 posts per week. He remains passionate about keeping animals and plants, right across the board: aquarium (fresh water and marine), terrarium, pond keeping, and small birds.

Frank Schäfer is married and has two daughters, born in 1989 and 1991.

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