, Volume 14, Issue 4, pp 413–417

Quantitative measurement of food selection

A modification of the forage ratio and Ivlev's electivity index
  • Jürgen Jacobs

DOI: 10.1007/BF00384581

Cite this article as:
Jacobs, J. Oecologia (1974) 14: 413. doi:10.1007/BF00384581


The forage ratio and Ivlev's electivity index are common measures to quantify food selection but the values of both indices depend not only on the extent of selection but also on the relative abundances of the food types in the environment. They are therefore useless when food types with different relative abundances are compared, or when the relation between selection and relative abundance is studied. Modified versions of both indices are proposed which are based directly on the rates of decrement (mortality) of the food due to feeding, and are independent of the relative abundance.

Copyright information

© Springer-Verlag 1974

Authors and Affiliations

  • Jürgen Jacobs
    • 1
  1. 1.Zoologisches Institut der Universität MünchenMünchenFederal Republic of Germany