Hermit crab shell-switching patterns have been used as case studies in vacancy chain theory (Lewis and Rotjan 2009), a body of theory originally developed by sociologists to understand how vacancies involving discrete, reusable, and limited resources such as apartments, jobs, and cars are transferred within human populations. When an individual gets a new resource, the vacancy thus created can propagate down the socioeconomic order through a series of interdependent events, with the result that many individuals can benefit “downstream” through the acquisition of new physical resources or social positions. Rotjan et al. (2010) describe 2 types of hermit crab vacancy chains, synchronous and asynchronous. These 2 types of vacancy chains are both social and stand in direct contrast to solitary shell interactions involving a single crab and a single shell. Synchronous vacancy chains occur after several crabs adjacent to an available vacant shell have queued in decreasing size order; as soon as the largest crab switches into the vacant shell, a rapid series of sequential shell switches takes place. In contrast, in asynchronous vacancy chains individual crabs encountering a suitable vacant shell will switch and their discarded shells will later be discovered and occupied by other crabs. Thus, asynchronous vacancy chains do not involve social interactions or queue formation, and sequential shell switches take place over considerably longer time periods. In both cases, vacancy chains are terminated when the last shell discarded is of such low quality (too small or damaged) that all crabs reject it. In field observations, Rotjan et al. (2010) found that after investigation of a vacant shell that was too large, hermit crabs would remain near (within 50 cm) the shell rather than moving away immediately: crab waiting times ranged from several minutes to more than an hour, and up to 20 waiters at a time were present near the empty shell. Crabs exhibited waiting behavior at 55% (6 of 11) of stations with large vacant shells and at 100% (9 of 9) of stations with medium vacant shells. Waiters were observed at all stations where synchronous vacancy chains eventually occurred. (Rotjan et al. 2010 and references therein)
The Caribbean hermit crab (Coenobita clypeatus), also known as the soldier crab,[2] West Atlantic crab, tree crab, or purple pincher (due to the distinctive purple claw), is a species of land hermit crab native to the west Atlantic, Belize, southern Florida,[3] Venezuela, and the West Indies.[4]
Adults burrow and hide under the roots of large trees, and can be found a considerable distance inland.[3] As with other terrestrial crabs, they use modified gills to breathe air. Their shells help maintain the humidity necessary for gas exchange to function.[5] Typically, the Caribbean hermit crab's left claw is larger in size than its right claw and is purple in color. Female land hermit crabs release fertilized eggs into the ocean. The spawning (called "washing" in the English-speaking Caribbean) occurs on certain nights, usually around August.[2]
Caribbean hermit crabs are both herbivorous and scavengers.[6] In the wild, C. clypeatus feeds on animal and plant remains, overripe fruit, and faeces of other animals,[3] including the Mona ground iguana (Cyclura stejnegeri).[2] The West Indian top snail (Cittarium pica) shell is often used for its home, and the hermit crab can use its larger claw to cover the aperture of the shell for protection against predators.[3] As with other species of hermit crabs, C. clypeatus may engage in "shell fights" and can emit a chirping noise when stressed.[7]
This species is one of the two land hermit crabs commonly sold in the United States as pets, the other being the Ecuadorian hermit crab.[4][8] C. clypeatus has been confirmed to live as long as 12 years,[9] and some crab owners have claimed to have crabs live up to 40 years.[10]
The Caribbean hermit crab (Coenobita clypeatus), also known as the soldier crab, West Atlantic crab, tree crab, or purple pincher (due to the distinctive purple claw), is a species of land hermit crab native to the west Atlantic, Belize, southern Florida, Venezuela, and the West Indies.