Orientation experiments were carried out on
Talitrus saltator (Crustacea Amphipoda) at four points
along 3 km on a dynamic sandy beach inside the
Maremma Regional Park (Grosseto, Italy) to highlight
behavioural variation related to distance from a river
mouth, to erosion or accretion of shoreline, and to human
trampling on the beach. Tests were performed using
circular transparent Plexiglas arenas, contemporaneously
at the four points. Replicates were made in 2 different
months (September 2002 and May 2003), on 2–3
successive days, in the morning and afternoon. The
distributions of the angles of orientation were compared
for the different points and seasons, and multiple
regression analysis was performed to test the effects of
environmental and intrinsic variables on orientation.
Sandhoppers showed the highest scatter at the eroded
shoreline, intermediate scatter at the accreting beach
most distant from the river mouth, and consistent orientation
seaward at the least disturbed point. Orientation
of sandhoppers was significantly affected by season,
global radiation, time of day, distance from the river
mouth, and human trampling. Sex and air humidity
were of minor significance in the multiple regression
model. The results, on the one hand, confirm plasticity
in orientation of sandhoppers living on a dynamic
shoreline, and on the other hand, show that variation in
orientation could potentially be used as a bioindicator of
shoreline changes.
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