P. B. Adler, D. A. Raff, and W. K. Lauenroth, The effect of grazing on the spatial heterogeneity of vegetation, Oecologia, vol.128, pp.465-479, 2001.

M. C. Appleby, Social rank and food access in red deer stags, Behaviour, vol.74, pp.294-309, 1980.

R. Arditi and B. Dacorogna, Optimal foraging on arbitrary food distribution and the definition of habitat patches, Am. Nat, vol.131, pp.837-846, 1988.

G. W. Arnold and M. L. Dudzinski, Ethology of freeranging domestic animals, 1978.

J. P. Bakker, The impact of grazing on plant communities, pp.137-184, 1998.

D. R. Bazely and C. V. Ensor, Discrimination learning in sheep with cues varying in brightness and hue, Appl. Anim. Behav. Sci, vol.23, pp.293-299, 1989.

J. A. Beecham and K. D. Farnsworth, Animal group forces resulting from predator avoidance and competition minimisation, J. Theor. Biol, vol.198, pp.533-548, 1999.

S. Benhamou, Efficiency of area-concentrated searching behaviour in a continuous patchy environment, J. Theor. Biol, vol.159, pp.67-81, 1992.

S. Benhamou, Spatial memory and searching efficiency, Anim. Behav, vol.47, pp.1423-1433, 1994.

F. Blanc and M. Thériez, Effects of stocking density on the behaviour and growth of farmed red deer hinds, Appl. Anim. Behav. Sci, vol.56, pp.297-307, 1998.
URL : https://hal.archives-ouvertes.fr/hal-02683785

A. Boissy and B. Dumont, Interactions between social and feeding motivations on the grazing behaviour of herbivores: sheep more easily split into subgroups with familiar peers, Appl. Anim. Behav. Sci, vol.79, pp.233-245, 2002.
URL : https://hal.archives-ouvertes.fr/hal-02677642

E. L. Charnov, Optimal foraging, the marginal value theorem, Theor. Pop. Biol, vol.9, pp.129-136, 1976.

B. Dumont and A. Boissy, Grazing behaviour of sheep in a situation of conflict between feeding and social motivations, Behav. Proc, vol.49, pp.131-138, 2000.
URL : https://hal.archives-ouvertes.fr/hal-02692089

B. Dumont and D. R. Hill, Multi-agent simulation of group foraging in sheep: effects of spatial memory, conspecific attraction and plot size, Ecol. Model, vol.141, pp.201-215, 2001.
URL : https://hal.archives-ouvertes.fr/hal-02077149

B. Dumont and M. Petit, Spatial memory of sheep at pasture, Appl. Anim. Behav. Sci, vol.60, pp.43-53, 1998.
URL : https://hal.archives-ouvertes.fr/hal-02684254

B. Dumont, J. F. Maillard, and M. Petit, The effect of the spatial distribution of plant species within the sward on the searching success of sheep when grazing, Grass For. Sci, vol.55, pp.138-145, 2000.
URL : https://hal.archives-ouvertes.fr/hal-02690254

B. Dumont, P. Carrère, and P. D'hour, Foraging in patchy grasslands: diet selection by sheep and cattle is affected by the abundance and spatial distribution of preferred species, Anim. Res, vol.51, pp.367-381, 2002.
URL : https://hal.archives-ouvertes.fr/hal-02675130

G. R. Edwards, J. A. Newman, A. J. Parsons, and J. R. Krebs, The use of spatial memory by grazing animals to locate food patches in spatially heterogeneous environments: an example with sheep, Appl. Anim. Behav. Sci, vol.50, pp.147-160, 1996.

G. R. Edwards, J. A. Newman, A. J. Parsons, and J. R. Krebs, Use of cues by grazing animals to locate food patches: an example with sheep, Appl. Anim. Behav. Sci, vol.51, pp.59-68, 1997.

K. D. Farnsworth and J. A. Beecham, Beyond the ideal free distribution: more general models of predator distribution, J. Theor. Biol, vol.187, pp.389-396, 1997.

K. D. Farnsworth and J. A. Beecham, How do grazers achieve their distribution? A continuum of models from random diffusion to the ideal free distribution using biased random walks, Am. Nat, vol.153, pp.509-526, 1999.

S. D. Fretwell and H. L. Lucas, On territorial behaviour and other factors influencing habitat distribution in birds, Acta Biotheor, vol.19, pp.16-36, 1970.

M. J. Gibb, C. A. Huckle, R. Nuthall, and A. J. Rook, Effect of sward surface height on intake and grazing behaviour by lactating Holstein Friesian cows, Grass For. Sci, vol.52, pp.309-321, 1997.

L. Giraldeau and T. Caraco, Social Foraging Theory, 2000.

A. J. Parsons and B. Dumont,

L. Hewitson, The foraging behaviour of sheep in response to environmental uncertainty, 2002.

L. D. Howery, F. D. Provenza, R. E. Banner, and C. B. Scott, Social and environmental factors influence cattle distribution on rangeland, Appl. Anim. Behav. Sci, vol.55, pp.231-244, 1998.

S. P. Hubbell, The Unified Neutral Theory of Biodiversity and Biogeography, Monographs in Population Biology, vol.32, 2001.

P. J. Jarman, The social organisation of antelope in relation to their ecology, Behaviour, vol.48, pp.215-267, 1974.

K. A. Kershaw, Quantitative and Dynamic Plant Ecology, 2nded, 1973.

A. Lazo, Facteurs déterminants du comportement grégairedebovins retournés àl'étatsauvage, Rev. Ecol. (Terre & Vie), vol.47, pp.51-66, 1992.

E. Lecrivain, B. Leclerc, and A. Hauwuy, Consommation de ressources ligneuses dans un taillis de chênes par des brebis en estive, Reprod. Nutr. Dev, vol.30, pp.207-208, 1990.

C. A. Marriott and P. Carrère, Structure and dynamics of grazed vegetation, Ann. Zootech, vol.47, pp.359-369, 1998.
URL : https://hal.archives-ouvertes.fr/hal-00889737

R. M. May, Stability and complexity in model ecosystems, 1974.

. A. Newmanj and . Caracot, Cooperativeandnoncooperative bases for food-calling, J. Theor. Biol, vol.141, pp.197-209, 1989.

A. J. Parsons and D. F. Chapman, The principles of pasture growth and utilisation, Grass: its production and utilisation, pp.31-89, 2000.

A. J. Parsons, J. A. Newman, P. D. Penning, A. Harvey, and R. J. Orr, Diet preference of sheep: effects of recent diet, physiological state and species abundance, J. Anim. Ecol, vol.63, pp.465-478, 1994.

A. J. Parsons, J. H. Thornley, J. A. Newman, and P. D. Penning, A mechanistic model of some physical determinants of intake rate and diet selection in a two-species temperate grassland sward, Funct. Ecol, vol.8, pp.187-204, 1994.

A. J. Parsons, P. Carrère, and S. Schwinning, Dynamics of heterogeneity in a grazed sward, CAB International, pp.289-315, 2000.
URL : https://hal.archives-ouvertes.fr/hal-02765873

A. J. Parsons, S. Schwinning, and P. Carrère, Plant growth functions and possible spatial and temporal scaling errors in models of herbivory, Grass For. Sci, vol.56, pp.21-34, 2001.
URL : https://hal.archives-ouvertes.fr/hal-02669277

P. D. Penning, A. J. Parsons, J. A. Newman, R. J. Orr, and A. Harvey, The effects of group size on grazing time in sheep, Appl. Anim. Behav. Sci, vol.37, pp.101-109, 1993.

S. Prache, J. Damasceno, and G. Béchet, Preferences of sheep grazing down conterminal monoc ultures of Lolium perenne -Festuca arundinacea: test of an energy intake-rate maximization hypothesis, Multi-Function Grasslands -Quality Forages, pp.258-259, 2002.

G. D. Ruxton, Foraging on patches: are groups disadvantaged?, Oikos, vol.72, pp.148-150, 1995.

S. Schwinning and A. J. Parsons, A spatially explicit population model of stoloniferous N-fixing legumes in mixed pasture with grass, J. Ecol, vol.84, pp.815-826, 1996.

S. Schwinning and A. J. Parsons, The stability of grazing systems revisited: spatial models and the role of heterogeneity, Funct. Ecol, vol.13, pp.737-747, 1999.

A. M. Sibbald, L. J. Shellard, and T. S. Smart, Effects of space allowance on the grazing behaviour and spacing of sheep, Appl. Anim. Behav. Sci, vol.70, pp.49-62, 2000.

D. E. Spalinger and N. T. Hobbs, Mechanisms of foraging in mammalian herbivores: new models of functional response, Am. Nat, vol.140, pp.325-348, 1992.

D. W. Stephens, J. R. Krebs, and F. Theory, , 1986.

J. H. Thornley, A. J. Parsons, J. A. Newman, and P. D. Penning, A cost-benefit model of grazing intake and diet selection in a two-species temperate grassland sward, Funct. Ecol, vol.8, pp.5-16, 1994.

C. R. Thouless, Feeding competition between grazing red deer hinds, Anim. Behav, vol.40, pp.105-111, 1990.

P. Turchin, F. J. Odendaal, and M. D. Rausher, Quantifying insect movement in the field, Environ. Entomol, vol.20, pp.955-963, 1991.

E. D. Ungar and . Ingestive-behaviour, The Ecology and Management of Grazing Systems, CAB International, pp.185-218, 1996.

T. J. Valone, Patch information and estimation: a costof groupforaging, Oikos, vol.68, pp.258-266, 1993.

D. Ward and D. Saltz, Foraging at different spatial scales: Dorcas gazelles foraging for lilies in the Negev desert, Ecology, vol.75, pp.48-58, 1994.