Behaviour of the Soldier Crab — Cameron 
No displacement activity was observed in any 
other circumstances. 
DISCUSSION 
Several aspects of the behaviour of M. longi- 
carpus are of interest. It would appear that the 
preliminary feeding phase may be regarded as 
appetitive feeding. Normal feeding does not 
take place until completion of the trek. The ob- 
vious result of trekking is that the crabs move 
from the upper levels of the beach to the more 
moist areas. Altevogt (1957) postulated that 
all ocypodid crabs possessing spooned setae on 
the mouthparts select nutritive material from 
the sand by the "flotation” method he observed 
in Uca spp. Water is lost continuously through 
ingestion, evaporation, and in the discarded pel- 
lets. Miller ( 1961 ) investigated this topic for 
several species of Uca and concluded that the 
need for water is reflected by the moist condi- 
tion of the material from which these crabs 
prefer to feed. This appears to be the case for 
M. longicarpus. Not only do soldier crabs pos- 
sesses dense spoon-tipped setae, but also they 
frequently feed in depressions and in run-off 
channels. 
Trekking is most obvious on wide, gently 
sloping beaches where the crabs may remain on 
the surface for as long as 4 Vi hr. Where the 
beach is narrower and of steeper slope, they do 
not remain on the surface for such lengths of 
time, and they generally emerge earlier with 
respect to the time of low water than do those 
inhabiting the wider flats. On beaches of un- 
usual configuration, such as those at the mouth 
of the Pine River, the direction of the trek is 
determined by the proximity of extensive drain- 
age channels. Moving down the beach would 
bring them to the elevated sand bars. From the 
bars to the river the beach slopes in the normal 
way, and the crabs in this area trek down in the 
usual fashion. 
When feeding has ceased, the army wander- 
ing phase takes place. In some respects, the be- 
haviour of soldier crabs in this phase resembles 
that of Uca in the "nonaggressive wandering 
phase” described by Crane (1958). While it is 
evident that the aggregations in which feeding 
takes place subserve coverage of a widely dis- 
233 
persed food supply, the presence of the animals 
on the surface after feeding has ceased is enig- 
matic. Whatever are the physiological functions 
performed at this stage, they must be of con- 
siderable significance in view of the energy ex- 
pended in wandering about the beach, and of 
the danger from predators to which the aggre- 
gations are exposed. These phenomenal aggre- 
gations, in which the individuals perform no 
visible activity other than walking, may be an 
example of epideictic display (Wynne-Edwards, 
1962). 
Threat display is associated with competition 
for space, the space being a hole occupied by 
one crab and intruded into by another. Occu- 
pancy of a hole, however temporary, appears to 
be the manifestation of a poorly developed ter- 
ritoriality, and for this reason the threat display 
must be considered reproductive fighting. Tin- 
bergen (1952) remarked that displacement 
activities occur most frequently during boun- 
dary disputes. No instance was observed of 
either of the participants in a threat display 
subsequently performing displacement activity. 
This is not unexpected, in view of the transitory 
nature of soldier crab "territory,” which is based 
on occupancy of a hole and not on construction 
and maintenance of a permanent burrow. 
There are similarities between the intertidal 
behaviour patterns of M. longicarpus and Uca 
spp. (Crane, 1958). The activities of both are 
organised into a series of phases. There is a 
temporal separation of feeding, and of other 
activities. Although there is nothing comparable 
with the waving display of Uca in the behaviour 
of M. longicarpus, the occurrence in the latter 
of threat display, and its nature, are of interest. 
SUMMARY 
1. Mictyris longicarpus performs a sequence 
of phases of activity during the intertidal pe- 
riod: subterranean activity, emergence, prelimi- 
nary feeding, trekking down the beach, feeding, 
army wandering, return up the beach, aggressive 
wandering, return to subterranean burrows. 
2. Dense, elaborate spoon-tipped setae are 
present on the mouthparts of M. longicarpus . 
3. Wandering in armies occurs after feeding 
has ceased. Adult males comprise the majority 
