Timescales alter the inferred strength and temporal consistency of intraspecific diet specialization

Oecologia
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Abstract

Many populations consist of individuals that differ substantially in their diets. Quantification of the magnitude and temporal consistency of such intraspecific diet variation is needed to understand its importance, but the extent to which different approaches for doing so reflect instantaneous vs. time-aggregated measures of individual diets may bias inferences. We used direct observations of sea otter individuals (Enhydra lutris nereis) to assess how: (1) the timescale of sampling, (2) under-sampling, and (3) the incidence- vs. frequency-based consideration of prey species affect the inferred strength and consistency of intraspecific diet variation. Analyses of feeding observations aggregated over hourly to annual intervals revealed a substantial bias associated with time aggregation that decreases the inferred magnitude of specialization and increases the inferred consistency of individuals’ diets. Time aggregation also made estimates of specialization more sensitive to the consideration of prey frequency, which decreased estimates relative to the use of prey incidence; time aggregation did not affect the extent to which under-sampling contributed to its overestimation. Our analyses demonstrate the importance of studying intraspecific diet variation with an explicit consideration of time and thereby suggest guidelines for future empirical efforts. Failure to consider time will likely produce inconsistent predictions regarding the effects of intraspecific variation on predator–prey interactions.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Timescales alter the inferred strength and temporal consistency of intraspecific diet specialization
Series title Oecologia
DOI 10.1007/s00442-014-3213-2
Volume 178
Issue 1
Year Published 2015
Language English
Publisher Springer
Contributing office(s) Western Ecological Research Center
Description 14 p.
First page 61
Last page 74
Online Only (Y/N) N
Additional Online Files (Y/N) N