Agriculture, Ecosystems and Environment 89 (2002) 253–259 Short communication Foraging activity of the carabid beetle Pterostichus melanarius Ill. in field margin habitats Elisabeth Fournier ∗ , Michel Loreau Laboratoire d’Ecologie, UMR 7625, Ecole Normale Supérieure, 46 rue d’Ulm, F-75230 Paris Cedex 05, France Received 26 October 2000; received in revised form 8 March 2001; accepted 21 March 2001 Abstract The foraging activity of the carabid beetle Pterostichus melanarius was studied in a capture–recapture experiment in field margin habitats. Two rectangular enclosures were installed over a succession of habitats with a decreasing prey availability: a hedge, a mixed crop strip and an adjacent crop culture. Marked starved and satiated individuals were released in the enclosures and recaptured during 8 days. Initial satiation state had a significant effect on activity. Also, the initial displacements of beetles depended both on the habitat and on the initial satiation state. P. melanarius appeared to have flexible habitat-use, depending mainly on three factors: the satiation state, the habitat preference of the species, and the prey availability in the habitat. © 2002 Elsevier Science B.V. All rights reserved. Keywords: Capture–recapture; Carabidae; Field margins; Foraging; Pterostichus melanarius; France 1. Introduction Research in sustainable agriculture has stressed the importance of undisturbed field margins in in- tensive agro-ecosystems for the maintenance and enhancement of populations of predatory arthropods (Duelli, 1990; Hassal et al., 1992). Ground beetles (Coleoptera, Carabidae) have often been used to study the ecological effects of such field boundaries (Burel, 1992; Lys, 1994; Rykken et al., 1997). Many studies have shown that the spatial distributions and dynam- ics of carabid species are modified by the presence of various kinds of undisturbed areas within agricul- ∗ Corresponding author. Present address: INRA Unit´ e de Patholo- gie V´ eg´ etale, Route de Saint Cyr, F-78000 Versailles, France. Fax: +33-1-30-83-31-95. E-mail address: elisabeth.fournier@versailles.inra.fr (E. Fournier). tural fields. Several hypotheses have been proposed to explain these changes, such as provision of refuge sites in the case of intensive agricultural perturbations (Wallin, 1987), provision of breeding or overwinter- ing areas (Desender, 1982), establishment of corridors for dispersion (Petit and Burel, 1998), and enhance- ment of prey availability (Zangger, 1994). This work aimed to study how the foraging strategies of the carabid beetle Pterostichus melanarius are modified in new field margins habitats. Several authors hypothesised that in carabids, forag- ing depends mainly on hunger level (den Boer, 1986; Mols, 1987, 1988). This hypothesis states that dis- placements are modified by prey intake, and assumes that (1) starved individuals are more active than sati- ated ones, and (2) this foraging activity is to search for prey. However, experimental studies of foraging in natural conditions remain scarce. 0167-8809/02/$ – see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0167-8809(01)00216-X