title: Use of δ13C values to determine vegetation selectivity in East African herbivores.
abstract: The quantitative plant species composition of the rumen contents of a large number of individuals from eight East African herbivores was determined by direct visual analysis. All plant species were classified as either C3or C4, and an estimated δ13C for the rumen sample was calculated. This estimated value was compared to a measured value determined directly from rumen subsample. The two methods of determining quantitative C3and C4composition differed by less than 1%, and the isotopic analysis has the advantage of being rapid and totally objective.The isotopic analysis allowed us to differentiate between grazers and browsers and to determine the quantitative dependence of each animal on C3and C4photosynthetic types. Kongoni, wildebeest, cattle, and sheep were nearly pure grazers on the Athi Kapiti Plains; and the Grant's gazelle were predominantly browsers. Thompson's gazelle, goast and impala were intermediate. The species most dependent upon browse showed a marked and rapid shift to grass within a few days following rain. This isotopic method may have general utility in the study of East African ecology.
authors.affiliation: Department of Biology, Augustana College, 57102, Sioux Falls, SD, USA.
authors.forename: Larry L
authors.initials: LL
authors.lastname: Tieszen
authors.affiliation: Department of Biology, Augustana College, 57102, Sioux Falls, SD, USA.
authors.forename: Dennis
authors.initials: D
authors.lastname: Hein
authors.affiliation: , Lundhojvej 15, 8680, Ry, Denmark.
authors.forename: Svend A
authors.initials: SA
authors.lastname: Qvortrup
authors.affiliation: Physics and Engineering Laboratory, Department of Scientific and Industrial Research, Lower Hutt, New Zealand.
authors.forename: John H
authors.initials: JH
authors.lastname: Troughton
authors.affiliation: Department of Botany, University of Nairobi, Nairobi, Kenya.
authors.forename: Simeon K
authors.initials: SK
authors.lastname: Imbamba