4.5. Flora of interest to the Mountain Gorilla
We have reported throughout this study that 40 species of
plants are eaten by gorillas. Species widely distributed over the transect
were: Basella alba, Desmodium rependum, Discopodium
penninervium, Impatiens burtonii, Impatiens
purpureo-violacea, Mimulopsis solmsii, Urera
hypselodendron, Tacazze apiculata, Thalictrum
rhynchocarpum and Vernonia auriculifera. Note also that the
herbaceous plant species consumed by mountain gorilla were present in more or
less stable composition along the line transect excluding the following:
Begonia meyerijabannis (segment 6), Carduus nyasanus var
nyasanus (segment 5), Ensete Ventricusum (segment 4), Lactuca
sp. (segment 6), Lobelia giberroa (segment 7), Rudia
cordifolia (segment 2) and Vernonia adolfi-fridoricii (segment
7). These are indeed specific to particular segments and are therefore the less
widely distributed on the line transect. These species are those which respond
to the rule of altitudinal distribution and were found in specific ranges of
altitude.
Figure 30 compares the species eaten by gorillas in the whole
herbaceous flora in the Mwaro corridor.
The highest elevations are specifically the most diverse in
herbaceous species. Accordingly, species eaten by gorillas follow the same
trend. Thus, it seems that the presence of more species eaten by gorillas at
higher altitude may explain why the mountain gorillas prefer high altitudes as
their ecological niche where they may find most of their foods and at the same
time avoid food competition with other primates present in high density at
lower altitudes.
Biodiversity survey of Mwaro corridor, Altitudinal
distribution of the vegetation and assessment of Gorilla food
availability
Number of species
40
20
60
50
30
10
0
Segl
ot herbacées
Herbaceous species Esp. Consommées
Species eaten by Gorillas
Seg2
Seg3
ype segme
Segments
Seg4
Seg5
Seg6
Seg7
Page 46
Figure 30. Distribution of herbaceous species eaten by
mountain gorilla in different segments
4.6. Comparison of plant species consumed by gorillas
according to different sites
Another study of plant species of interest to the gorillas is
the one carried out in Kahuzi-Biega National Park (Yamagiwa et al., 2004). It
brings together 236 items from 116 species identified as food for gorillas
inhabiting the montane forest of Kahuzi-Biega National park. Of these species,
44 are consumed for their fruits, 5 for their seeds, 80 for their leaves, 1 as
a young plant, 9 for their flowers, 6 for their the roots, 32 for their barks,
2 unidentified dead wood and 6 for their stems.
Comparing our results with those of Yamagiwa et al. (2004),
the most species reported as gorilla food in the Mwaro corridor were also
reported in Kahuzi-Biega. To name just a few: Discopodium penninervium,
Basella alba, Urera hypselodendron and Ensete ventricosum among
others. There is also a large number of species in Mwaro not reported as
consumed by the gorillas in Virunga National Park, while reported as eaten in
Kahuzi-Biega National Park. It is for example: Schefflera goetzenii
and Jasminum abyssinicum
A similar study carried out in Bwindi Impenatrable National
Park in Uganda (Ganas et al., 2004) compared the species eaten by mountain
gorillas following an altitudinal gradient, putting more emphasis on the
differentiation of gorilla feeding behaviour according to the consumed parts of
the plant. According to this study, there is a very marked difference between
the plant parts eaten by gorilla with altitude.
In lowland forest, gorillas eat more woody items and fruits
than in high altitude zones. Our study conducted at high altitude showed that
leaves and fruits are by far more heavily consumed by the gorilla (Table 14)
despite that Elegart (2004), after examining parts eaten by gorillas in each
species of plants, it is found that leaves and fruit had negligible value.
Biodiversity survey of Mwaro corridor, Altitudinal
distribution of the vegetation and assessment of Gorilla food
availability
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