Shell Selection and Invasion Rates
Some Pacific Hermit Crabs
GORDON H. ORIANS and CHARLES E. KING
ABSTRACT : Three species of littoral hermit crabs from Horseshoe Cove, Bodega
Head, Sonoma County, California, and three sublittoral pagurids from Chinimi
Island, Eniwetok Atoll, Marshall Islands, have been examined with respect to their
shell selection and invasion rates.
Periodic removal of crabs from marked areas resulted in
By comparison of actual collection patterns
predictable from the alternates of density dependence and density independence,
there is an indication that the observed immigration rates result from density-
dependent dispersal. While our data are not conclusive, the method presented is of
interest and of possible utility for examining problems of this nature.
Shell selection is discussed from the bases of both laboratory and field observa-
tions. Each of the species is shown to utilize the shells of different gastropods with
Finally, behavioral aspects are examined as they relate to the distribution of the
California hermit crabs.
SHELLS of various species of gastropod molluscs
constitute a necessarycomponent in the environ-
ment of pagurid crabs. In addition to housing
the crab the shell may act as an
determinant of behavior; for instance, several
species will not feed unless in a shell (Allee
and Douglis, 1945; Brightwell, 1952). Different
species of pagurids regularly utilize different
species of shells and it has been suggested that
shell availability may be a limiting factor for
some species (Provenzano, 1960).
This paper reports on observations of shell
utilization by six species of Pacific hermit crabs
and on some simple laboratory experiments on
shell selection. In addition, a number of removal
and repopulation experiments were performed.
Orians worked mainly at Horseshoe Cove, Bo-
dega Head, Sonoma County, California, during
the summer of 1957, and King at Chinimi Island
of Eniwetok Atoll during the summer of 1961.
The study area at Horseshoe Cove consisted
of a section of rocky, shelving shore partially
Dept. of Zoology, Univ . of Washington, Seattle.
Manuscript received January 31, 1963 . Orians' research
was carried out under the auspices of the Dept. of
Zoology, Univ. of California, Berkeley. King's research
was supported by the U. S. Atomic Energy Commis-
sion at their Eniwetok Marine Biological Laboratory.
protected from heavy ocean swell, with an abun-
dance of small tidal pools at high and medium
ranges. Twenty-seven pools in the
tidal range 2.5-4.5
ft above. datum
mean low water) and subjected to long periods
of exposure at low tides, were selected because
they were easily reached at most tides. They
ranged in length from 0.43 to 9.5 m and in
depth from 15 cm to approximately 1 m.·Plant
cover varied from virtually nothing to dense
algal growth covering the bottoms and sides of
the pools. During the period of study, tempera-
tures never rose above 17 C in the lower and