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Prey Selection by an Apex Predator: The Importance of Sampling Uncertainty

Davis, M.L.; Stephens, P.A.; Willis, S.G.; Bassi, E.; Marcon, A.; Donaggio, E.; Capitani, C.; Apollonio, M.

Prey Selection by an Apex Predator: The Importance of Sampling Uncertainty Thumbnail


M.L. Davis

E. Bassi

A. Marcon

E. Donaggio

C. Capitani

M. Apollonio


The impact of predation on prey populations has long been a focus of ecologists, but a firm understanding of the factors influencing prey selection, a key predictor of that impact, remains elusive. High levels of variability observed in prey selection may reflect true differences in the ecology of different communities but might also reflect a failure to deal adequately with uncertainties in the underlying data. Indeed, our review showed that less than 10% of studies of European wolf predation accounted for sampling uncertainty. Here, we relate annual variability in wolf diet to prey availability and examine temporal patterns in prey selection; in particular, we identify how considering uncertainty alters conclusions regarding prey selection. Over nine years, we collected 1,974 wolf scats and conducted drive censuses of ungulates in Alpe di Catenaia, Italy. We bootstrapped scat and census data within years to construct confidence intervals around estimates of prey use, availability and selection. Wolf diet was dominated by boar (61.5±3.90 [SE] % of biomass eaten) and roe deer (33.7±3.61%). Temporal patterns of prey densities revealed that the proportion of roe deer in wolf diet peaked when boar densities were low, not when roe deer densities were highest. Considering only the two dominant prey types, Manly's standardized selection index using all data across years indicated selection for boar (mean = 0.73±0.023). However, sampling error resulted in wide confidence intervals around estimates of prey selection. Thus, despite considerable variation in yearly estimates, confidence intervals for all years overlapped. Failing to consider such uncertainty could lead erroneously to the assumption of differences in prey selection among years. This study highlights the importance of considering temporal variation in relative prey availability and accounting for sampling uncertainty when interpreting the results of dietary studies.


Davis, M., Stephens, P., Willis, S., Bassi, E., Marcon, A., Donaggio, E., …Apollonio, M. (2012). Prey Selection by an Apex Predator: The Importance of Sampling Uncertainty. PLoS ONE, 7(10), Article e47894.

Journal Article Type Article
Publication Date Oct 26, 2012
Deposit Date Jan 16, 2013
Publicly Available Date Aug 21, 2014
Journal PLoS ONE
Publisher Public Library of Science
Peer Reviewed Peer Reviewed
Volume 7
Issue 10
Article Number e47894


Published Journal Article (492 Kb)

Publisher Licence URL

Copyright Statement
© 2012 Davis et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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