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In the view to work out an integrated pest management system against 3 rodent species (Meriones sham, Gerbillus nanus, Psammomys obesus), pest of the saharian agriculture of Morocco, we had to perfect a sampling method of these mammals both light and relevent to the question. Two separate experimentations were undertaken to test a sampling method founded on trapping out on a strip. The first step consists of the analysis of data provided by Capture-Marking-Recapture operation of all the rodents on a 1 ha (100 χ 100 m) quadrat, subdivided in 10 χ 10 m unities. This operation allowed us to determine rationally the geometric characteristics of the strip, that is to say, a 100 χ 10 m strip made of 10 adjoining squares of 10 m side, each equiped with 4 Manufranee traps. During the second step of this experimentation, two sampling strips were superposed on the quadrat system and all the trapped rodents were removed. This operation allowed us to fixe the general timing of operations and, particularly, those of traps checking. Samplings by trapping out must be performed within 4 days with 2 daily trap checkings. These last characteristics were precised by results of a second experimentation wich consist of setting up 16 sampling strips. The limits of this linear trapping out sampling method are discussed mainly in the light of behavioural and landscape factors.Rέsumέ. -Pour developper une Strategie de l tte integree l'encontre de 3 especes de rongeurs (Meriones sham, Gerbillus nanus, Psammomys obesus), ravageurs de cultures de la zone saharienne marocaine, il importait de mettre au point une methode d'echantillonnage de ces mammiferes qui soit la fois lagere et pertinente I'ogard de la question posee. Deux experiences distinctes ont ete menees. La premiere a consiste realiser, au cours d'une premiere etape, sur un quadrat de un hectare de maille 10m χ 10m la capture, le marquage et la recapture de tous les rongeurs. Elle a permis de fixer rationnellement les caracteristiques geometriques de la b nde de piegeage (100m χ 10m subdivisee en carres unitaires de 10 m χ 10 m equipes chacun de 4 ratieres Manufrance). Au gre d'une deuxieme etape, grace au piegeage exhaustif de deux bandes echantillon superposees ce quadrat, il a ete possible d'opter de fagon fondee pour une sequence temporelle des operations d'echantillonnage. Ces resultats ont ete enrichis par Γ analyse de ceux provenant d'une deuxieme experience independante consistant en la pose de 16 bandes de pie- Mamntalia, t. 52, n° 2, 1988. Brought to you by |

In the saharian area of Guelmime (Morocco), 7 trap sampling systems were set side by side parallel to the Oued Sayad at a distance of 20 to 1280 m from it. The global trapping system allowed to catch 14 Meriones sham, 16 M. libycus, 29 Psammomys obesus, 4 Gerbillus nanus, 3 Eliomys occidentalis and 1 Elephantulus rozeii.The highest abundance and diversity of micromammals was found in an area located at 40-80 m far from the Oued and caracterized by a low salted soil surrounded by a vigourous Chenopodiacea association punctuated with clumps of Tamarix gallica. The number of trapped animals decreased with the progressive vanishing of T. gallica, the decline in the size and volume of Chenopodiacea clumps and the increasing salt content of the size and volume of Chenopodiacea clumps and the increasing salt content of the soil. It was nul when a Plombaginacea (Limoniastrum ifiniensis), a well fitted plant for salted soil, took the place of Chenopodiacea.Relationships between the microgeographical abundance of mammals and the vegetation (antipredator protection, Oued flood protection, trophic resources) are discussed.

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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.