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

Table 2: δ 13 C values and % C4 from fresh faecal samples of elephants and hippopotami in
Kenya, East Africa. Coefficient of variation (CV) is
expressed as a percentage of the δ 13 C (Tieszen and Imbamba 1980: 240).
Amboseli National Park /Samburu Game Reserve/ Aberdares National Park
Mean CV % C4 Mean CV % C4 Mean CV % C4
(%)
(%)
(%)
Elephant -17.1 14.1 70 -16.4 12.5 75 -26.5 1.7 10
Hippo -18.4 62
forested area, Aberdares National Park, the elephants exhibited a heavy reliance on C3
plants. The authors caution that sampling feces may overestimate the C4 as these plants
do not break down as well in the digestive tract.
In a study with a broader geographical scope, van der Merwe et al. (1988)
analyzed the bone collagen of elephants from twelve wildlife refuges in East and South
which spanned many types of habitats: primary rain forest, savanna woodland, and
desert. The results are given in Figures 38 and 39. A linear relationship was found
between tree density and the δ 13 C values. This is due to factors such as the availability of
browse in savanna woodland and forest, the dominance of C4 grasses in grassland
habitats verses C3 grasses in forests, and the “canopy effect” whereby the δ 13 C values in
forests are more negative than C3 plants in open woodlands (van der Merwe et al. 1988:
164-169). The variation among elephants within each refuge is very small, probably due
to the artificial boundaries of the refuges, as well as the clan-based social organization.
However, the C4 component is probably under-represented in collagen, since field studies
of the parks suggest elephants eat a greater amount of C4 grasses.
Another study published around this time was that of Sukumar et al. (1987), who
tested the bone collagen of Asian elephants for carbon isotopes and reported wide
individual variability (-11.1 to –20.8). The researchers related the variability to age, as
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