Landscape vision and zonal orientation in the Equatorial sandhopper Talorchestia martensii.

We investigate the role of the landscape in the zonal recovery of the Equatorial sandhopper Talorchestia martensii Weber. It is known that this species uses the sun and the magnetic compasses to return to the belt of damp sand of the beach following the shortest route (the sea-land axis). However, the sun is not always easy to use at Equatorial latitudes because of astronomical reasons (its zenithal culmination and its hourly azimuthal speed) at least during the central time of the day (around noon) and close to the equinox. Our experiments were performed in Kenya, during the equinoctial period. We tested adult individuals, belonging to Malindi (Kenya) population, in a confined environment with and without the vision of the landscape of their home beach and with the vision of the prominent landscape of a different-orientated shore (Temple Point). Releases were carried out with either natural or zeroed magnetic field. Results clearly show the importance of the landscape as an orienting factor mainly during the central hours of the day when it seems to assume a greater importance than magnetic cues.