Behavioural similarities in different species of sandhoppers inhabiting transient environments

On sandy shores, physical constraints are expected to be the main driving force in defining both the presence and behaviour of the suite of resident species. We tested the orientation of sandhoppers found on the Atlantic shores of Morocco, on two banks of an ephemeral river mouth, which presented different ecological characteristics. Replicates were carried out before and after summer, when a seasonal change of both natural and human-driven environmental features is expected, due to increasing temperatures, dryness and frequency of tourists. These features affected the two wadi banks differently, providing a natural set of environmental conditions to be tested. Three species were found at the site, each with a different distribution on the two banks: Africorchestia spinifera was found on both banks; Talorchestia brito on the left bank only and Talitrus saltator on the right bank only. Although the occurrence of sandhoppers decreased after summer, the multiple regression models developed from the orientation datasets and selected with the Akaike Information Criterion retained the same variables to explain the orientation of the individuals tested: environment (the river bank); intrinsic (the sex); and immediate (the time of the day) one. This highlighted the environment role, including human pressures, in shaping: a) the occurrence of sandhopper species; and b) a common behavioural strategy to cope with environmental changes, disregarding the species. The occurrence and behaviour of talitrids were thus at least partly independent of one another. These experiments also provided the first behavioural data for the species A. spinifera and its comparison with other supralittoral amphipod species.