Using daily ration models and stable isotope analysis to predict biomass depletion by herbivores.

Published online
11 Oct 2006
Content type
Journal article
Journal title
Journal of Applied Ecology
DOI
10.1111/j.1365-2664.2006.01207.x

Author(s)
Inger, R. & Ruxton, G. D. & Newton, J. & Colhoun, K. & Mackie, K. & Robinson, J. A. & Bearhop, S.
Contact email(s)
r.inger@udcf.gla.ac.uk

Publication language
English
Location
UK & Northern Ireland

Abstract

Food availability is one of the major factors governing the distribution of animals. Because animal numbers can in turn regulate the availability of food, the relationship between the two can be described in terms of resource depletion, which can be difficult to quantify. We present a novel method utilizing multisource stable isotope mixing models and a daily ration approach to predict the depletion of seagrass (Zostera spp.) by grazing light-bellied Brent geese Branta bernicla hrota at Strangford Lough, Northern Ireland. The model successfully predicted the depletion of Zostera spp. over the whole Lough compared with empirically derived estimates of biomass. Further, the model was able to predict biomass depletion over 2 years with different population sizes. The predicted quantities of Zostera consumed were not in agreement with previous studies, being considerably higher, but this may be explained in terms of the lower energetic value of Zostera at Strangford Lough compared with other sites. When reparameterized with energetic values from previous studies, the model predictions for Zostera consumption were comparable with estimates derived by standard techniques. Synthesis and applications. This approach offers a novel, efficient and widely applicable method to investigate the relationship between consumers and their food sources. It may have application in deriving site carrying capacities and in quantifying agricultural damage by consumers.

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