Comparaison des régimes alimentaires de trois espèces sympatriques de Gerbillidae en milieu saharien, au Maroc

Résumé En

The diet of three sympatric Gerbilline Rodents (Meriones shawi, Gerbillus nanus and Psammomys obesus) was compared in a desert area near Guelmin, southern Morocco. The identification of the plant dietary items was based on the epidermal cells recovered in the stomach contents of animals trapped at monthly intervals. Meriones shawi has a varied diet (42 plant species) whatever the season, but it feeds mostly on two of the most abundant species, supplementing this basic diet with a variety of other plants. The nature of its plant food is also variable ; leaves, flowers, fruit and seeds are consumed, and a few arthropods are added to the ration in summer. This diet allows this rodent to live in a variety of habitats, cultivated areas included. Psammomys obesus has a much more specialized diet, mostly made up of the leaves of a single species of Chaenopodiaceae, supplemented by a few annuals. Gerbillus nanus has a diet similar to that of M. shawi in late winter and spring, but G. nanus becomes predominantly a seed-eater during the summer. The diets of M. shawi and G. nanus are therefore the most similar, whereas those of G. nanus and P. obesus differ strikingly. The preferred plant species of these sympatric rodents are different, as well as the plant parts they select. Three different feeding stategies can be distinguished in this gerbilline community : (a) a seasonal mixed feeding strategy for G. nanus which shifts from leaves to seeds during the summer ; (b) a stable mixed feeding strategy for M. shawi which feeds on a few abundant perennial plants and the few annuals available all the year long ; and (c) a specialized feeding strategy f or P. obesus which limits itself to a single species of drought resistant plant. Although the staple food of the three rodent species studied is basically made up of a few common plants, these sympatric gerbillids manage to make use of the available plant resources during the driest period of the year in a way that prevents competition. The sprouting of a few grass species during the autumn apparently coincides with the initiation of the autumnal breeding season of these three gerbillids.