Temporal organization of foraging in two Mediterranean limpets, Patella rustica L. and P. coerulea L.

Abstract

The activity of two groups of Patella coerulea L. and P. rustica L. was monitored on the Tyrrhenian coast using an automatic recording device. The two species inhabit the rocky shores of the Mediterranean Sea and show different zonation patterns in the study area. The analysis of diel and tidal components of activity revealed an evident short-term rhythmicity with a marked preference for daytime high tide in P. coerulea and less in P. rustica. On the contrary, a marked positive correlation between activity and sea roughness was recorded for P. rustica, while P. coerulea movements are less correlated with sea state. Finally, long-term analysis of the activity pointed out the difference of the foraging strategies of the two species: the lower-shore P. coerulea performs short but regular foraging trips, while the upper-shore P. rustica carries out longer but irregularly timed excursions. The inactivity (starvation) periods of P. rustica are significantly longer than those of P. coerulea, but this is balanced in the former species by exploiting suitable algal grounds in the supralittoral zone where interspecific competition for food is very low.