Astronomical, landscape and climatic factors influencing oriented movements of Talitrus saltator in nature

 The present study was conducted on a Mediterranean beach (Burano, southern Tuscany, Italy) to examine the timing, orientation, and motivating and directing factors of the spontaneous movements of the sandhopper Talitrus saltator (Montagu, 1808). In April 1994, October 1994 and June 1995, during different moon phases, traps were positioned in the eulittoral zone, which intercepted sandhoppers when walking on the sand surface. At the same time environmental parameters were registered. Contemporaneously, orientation tests were carried out on active individuals using two arenas, one of which permitted a view of both sky and landscape and one which prohibited the landscape view. The results show landward migration after sunset, for juveniles later than for adults, nonoriented activity for 2 or 3 h after midnight and seawards zonal recovery before and after sunrise. The main microclimatic factor modulating activity was sand temperature, while the nonoriented activity between the two migratory movements seems to be endogenously determined. Both sky and landscape cues are used by sandhoppers for orienting their course, but the landscape view is sufficient and necessary on new moon nights. These results contribute to solution of the controversy on the mechanisms actually motivating sandhoppers in nature. Received: 24 September 1996 / Accepted: 25 October 1996