S. Cannicci et al., Short-range homing in fiddler crabs (Ocypodidae, genus Uca): A homing mechanism not based on local visual landmarks, ETHOLOGY, 105(10), 1999, pp. 867-880
This field study investigated the spatial strategies and homing ability of
two East African fiddler crabs, Uca lactea annulipes and Uca vocans hesperi
ae, using various experimental procedures. A clear-cut spatial segregation
between the two species was observed, with U. l. annulipes occupying areas
even a few centimetres above U. v. hesperiae. Females of both species were
extremely faithful to their holes while the males exhibited behavioural dif
ferences. U. l. annulipes males were quite faithful to their holes; in cont
rast, U. v. hesperiae males, during a single low tide, visited several hole
s which they did not defend. Two displacement experiments were conducted in
order to identify the stimuli that fiddler crabs use in their homing. In t
he 'dislocation experiment', the crabs were moved (by hand) 1 or 2m away fr
om their refuge and released. None of these crabs returned to its burrow an
d, moreover, the initial directions they followed were not homeward orienta
ted. In the 'translation experiment', the crabs were passively translated w
hile actively feeding. When the crabs attempted to go 'home' after the tran
slation, they darted along a straight path that led them to points that wou
ld have corresponded to their homes if the translation had not taken place.
After this first response crabs then commenced searching strategies that l
ed half of them home. Short-range homing seems to depend strongly on inform
ation actively gathered during the outward journey, other than local visual
landmarks.