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Characterisation by fractal analysis of foraging paths of ewes grazing heterogeneous swards

Authors :
Pascal Carrère
René Baumont
F. Garcia
Jean-François Soussana
Unité de Recherches sur les Herbivores (URH)
Institut National de la Recherche Agronomique (INRA)
UR 0874 Unité de recherche Agronomie de Clermont
Institut National de la Recherche Agronomique (INRA)-Environnement et Agronomie (E.A.)-Ecologie des Forêts, Prairies et milieux Aquatiques (EFPA)
Institut National de la Recherche Agronomique (INRA)-Unité de recherche Agronomie de Clermont (URAC)
Source :
Applied Animal Behaviour Science, Applied Animal Behaviour Science, Elsevier, 2005, 93, pp.19-37
Publication Year :
2005
Publisher :
HAL CCSD, 2005.

Abstract

On grasslands, herbivores make a trade-off between the quality and the quantity of their intake. They improve their searching efficiency by modulating their foraging velocity and/or their path sinuosity through the perception of their feeding environment. The aim of this study was to test the pertinence of fractal analyses of foraging paths in order to improve the understanding of spatial utilisation at grazing. By the analysis of grazing paths of herbivores grazing a continuously distributed and spatially limited resource, we aimed to identify the spatial scales at which the animals perceive heterogeneity of the sward, and to characterise how sheep modulate their foraging paths through resource abundance and heterogeneity. Two groups of five dry ewes, grazing two plots of contrasting areas from April to the end of September 2000, were studied. On the smaller plot (1500m 2 ), the application of a high stocking rate (HSR) produced a resource of good quality but low quantity, and on the larger plot (3000m 2 ) a low stocking rate (LSR) created a sward of low quality but good quantity. We show that on initially homogeneous swards, sheep exhibited correlated random walks, reducing movement quantities to achieve their intake. After a few weeks of grazing, vegetation structure become more complex and sheep modulated their foraging paths through resource abundance and/or sward structure. We identified a breakpoint at 5m for which fractal dimension is always low. At lower scales (below 5m), the modulation of sinuosity was not linked to sward abundance and structure, and sheep adapted grazing behaviour at bite and feeding station scales. At higher scales (above 5m), modulation of grazing activity was achieved through path sinuosity in relation to perception of the environment. Grazing paths were tortuous on tall swards in summer, and straighter on heterogeneous, well-structured swards showing visual cues in autumn. Fractal dimension of grazing paths proved to be a synthetic measurement, which allowed identification of a hierarchical threshold in the spatial adaptation of foraging behaviour in domestic herbivores at grazing.

Details

Language :
English
ISSN :
01681591 and 18729045
Database :
OpenAIRE
Journal :
Applied Animal Behaviour Science, Applied Animal Behaviour Science, Elsevier, 2005, 93, pp.19-37
Accession number :
edsair.doi.dedup.....15417b2d0cd5accbf9e58c77c1e85d6d