34
M. J. WELLS
Laboratory studies of groups of individuals show the evolution of
stable dominance orders, which imply that the animals can both
recognize their neighbours and remember the results of past fights.
Dominance-subordinance relationships have been studied in most detail
in freshwater crayfish (Bovbjerg, 1963; Lowe, 1956; Penn and Fitzpatrick, 1963), but a single account (Douglis, 1950) dealing with
Homarus amerimnus Ml. Edw. indicates a similar state of affairs in
marine forms. Bovbjerg (1960) reports that dominance orders in
Pachygrapsus depend on size and sex; individuals fight and refuse
to share shelters under water, but will aggregate when out of it. Among
fiddler crabs, where the behavioural background is perhaps better
known than in other crustaceans (vide Altevogt, 1957a, b ; Crane,
1967,1958) it appears that social dominance is mainly dependent on the
behavioural phase of the individuals concerned, and since this changes
over a period of hours or days, no stable relationships are built up.
Occasionally, however, “ an individual ( U m maracoani (Latreille))
just past a long-maintained display phase was still dominant to one or
more displaying males which he had previously dominated” (Crane,
1968).
The holding of a sizable territory, or the return to a particular home
or axea after expeditions in search of food or mates are indications of
individual learning inasmuch as the individual must recognize its own
immediate surroundings. It is generally believed that many decapods
have particular homes and that the males sometimes defend territories.
In at least some cases this is illusory. Fiddler crabs, which at first
sight certainly appear to stick to particular burrows, defend their
holes only when in the active display phase. At other times they
wander widely ; there is no indication of permanent attachment to a
particular area (Crane, 1968). In fact, information on homing is
difficult to collect and the belief that individual decapods have lairs to
which they return appears to rest mainly on cases where recognizable
and usually large individuals have been found in the same crevice on
successive occasions. It is not always certain that the animals were
doing more than finding lodgement in the only suitable hole in the vicinity. Recent investigations have given conflicting results. Lindberg
(1966), for example, in mark and release experiments with some 2000
Panulirus, caught and observed underwater, notes only two occasions
on which lobsters appeared to be defending a territory; most of the
animals of whatever size moved about in groups, aggregating where the
shelter was big enough to hold more than one, and travelling mainly
at night over considerable distances. Of 160 individuals marked and
displaced 2-6 miles along the coast or out to sea, only two were sub-
M. J. WELLS
Laboratory studies of groups of individuals show the evolution of
stable dominance orders, which imply that the animals can both
recognize their neighbours and remember the results of past fights.
Dominance-subordinance relationships have been studied in most detail
in freshwater crayfish (Bovbjerg, 1963; Lowe, 1956; Penn and Fitzpatrick, 1963), but a single account (Douglis, 1950) dealing with
Homarus amerimnus Ml. Edw. indicates a similar state of affairs in
marine forms. Bovbjerg (1960) reports that dominance orders in
Pachygrapsus depend on size and sex; individuals fight and refuse
to share shelters under water, but will aggregate when out of it. Among
fiddler crabs, where the behavioural background is perhaps better
known than in other crustaceans (vide Altevogt, 1957a, b ; Crane,
1967,1958) it appears that social dominance is mainly dependent on the
behavioural phase of the individuals concerned, and since this changes
over a period of hours or days, no stable relationships are built up.
Occasionally, however, “ an individual ( U m maracoani (Latreille))
just past a long-maintained display phase was still dominant to one or
more displaying males which he had previously dominated” (Crane,
1968).
The holding of a sizable territory, or the return to a particular home
or axea after expeditions in search of food or mates are indications of
individual learning inasmuch as the individual must recognize its own
immediate surroundings. It is generally believed that many decapods
have particular homes and that the males sometimes defend territories.
In at least some cases this is illusory. Fiddler crabs, which at first
sight certainly appear to stick to particular burrows, defend their
holes only when in the active display phase. At other times they
wander widely ; there is no indication of permanent attachment to a
particular area (Crane, 1968). In fact, information on homing is
difficult to collect and the belief that individual decapods have lairs to
which they return appears to rest mainly on cases where recognizable
and usually large individuals have been found in the same crevice on
successive occasions. It is not always certain that the animals were
doing more than finding lodgement in the only suitable hole in the vicinity. Recent investigations have given conflicting results. Lindberg
(1966), for example, in mark and release experiments with some 2000
Panulirus, caught and observed underwater, notes only two occasions
on which lobsters appeared to be defending a territory; most of the
animals of whatever size moved about in groups, aggregating where the
shelter was big enough to hold more than one, and travelling mainly
at night over considerable distances. Of 160 individuals marked and
displaced 2-6 miles along the coast or out to sea, only two were sub-