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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Territory size decreases minimally with increasing food abundance in stream salmonids: Implications for population regulation (2017)
Titre original:	Territory size decreases minimally with increasing food abundance in stream salmonids
Auteurs :	James W. A. Grant, Auteur ; Laura K. Weir, Auteur ; Stefán Ó. Steingrímsson, Auteur
Type de document :	Article
Dans :	Journal of Animal Ecology (86(6) November 1, 2017)
Article en page(s) :	1308-1316
Langues:	Anglais
Mots-clés:	contiguous territories ; density limitation ; elastic disc model ; population density ; stream salmonids ; territoriality
Résumé :	* How the local density of territorial animals responds to changes in food abundance will depend on the flexibility of territory size. Quantitative estimates of territory size over a broad range of food abundance are relatively rare because of the difficulty of measuring food abundance in the wild. * Stream salmonids are an ideal model system for investigating flexibility in territory size, because food abundance can be quantified in the field and manipulated in the laboratory. We conducted a meta-analysis to test whether territory size decreases with increasing food abundance, and a mixed model analysis to test among three competing predictions: with increasing food abundance, territory size will be (1) fixed—the slope of a regression of log territory size vs. log food abundance = 0; (2) flexible and decreasing, as if individuals are defending a fixed amount of food—a slope = −1; and (3) initially compressible, but with an asymptotic minimum size—a slope between 0 and −1. * We collected data from 16 studies that manipulated or measured food abundance while monitoring changes in territory size of young-of-the-year salmonids; 10 were experimental laboratory studies, whereas six were observational field studies. * Overall, territory size decreased significantly with increasing food abundance; the weighted average correlation coefficient was −0.31. However, the estimated slope of the relationship between log territory size and log food abundance was only −0.23, significantly different from 0, and also significantly shallower than −1. * Our estimated slope suggests that attempts to increase the density of territorial salmonids by increasing food abundance and reducing territory size will be inefficient; a 20-fold increase in food abundance would be required to double population density. Our analysis may also have implications for other species with a territorial mosaic social system—i.e. contiguous territories. In these social systems, social inertia will dampen any effects of changes in food abundance on the local density of settlers, compared to non-territorial species or those with non-contiguous territories.
En ligne :	http://onlinelibrary.wiley.com/doi/10.1111/1365-2656.12737/abstract

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