Tracing the Source of the Elephant And Hippopotamus Ivory from ...

Chapter 9
A Review of Stable Isotope Ratio Studies for Modern Populations of Elephants
and Hippopotami
Having considered the mechanics of isotope analysis in Chapter Six, and the diet
and ecological requirements of hippopotami and elephants (Chapters Seven and Eight) to
better interpret these analyses, I now turn to take a brief look at previous isotopic research
on elephants (there is virtually none on hippopotamusi) to consider past successes.
Research on elephants has focused primarily on diet, utilizing stable carbon and nitrogen
isotopes (Tieszen and Imbamba 1980; Sukumar et al. 1987; van der Merwe et al. 1988;
Sukumar and Ramesh 1992, 1995; Koch et al. 1995; Ishibashi et al. 1999). More
germane to the present investigation are several studies using additional isotopes such as
strontium and lead to illustrate the potentiality for sourcing illegally poached ivory (van
der Merwe et al 1990; Vogel et al. 1990).
Tieszen and Imbamba (1980) were one of the first to apply isotopic analysis to
elephants (cf. Heaton et al. 1986 for another seminal article), and were the only
researchers to investigate hippopotami isotopically. They measured δ 13 C values from
fecal samples of a number of East African herbivores. In the lowlands of East Africa all
the grasses are C4, so they were able to estimate the percentage of browse (C3) to graze
(C4) for the animals. As expected, elephants exhibited a generalized feeding pattern,
utilizing C3 and C4 with high individual variability in percentages of each (Table 2).
Hippopotami have a high C4 component as well, but not as high as anticipated. In one
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