"Rudy Canoza" > wrote in message ...
> Sympatric populations of lowland gorillas (Gorilla
> gorilla gorilla) and chimpanzees (Pan troglodytes
> troglodytes) in the Lopé Reserve in central Gabon
> consumed insects at similar average frequencies over a
> 7-year period (30% versus 31% feces contained insect
> remains). Data came mostly from fecal analysis
> supplemented by observation and trail evidence. The
> weaver ant (Oecophylla longinoda) was the species eaten
> most frequently by both gorillas and chimpanzees. Other
> species of insects wore eaten but there was virtually
> no overlap: Chimpanzees used tools to eat Apis bees
> (and their honey) and two large species of ants;
> gorillas ate three species of small ants. Thus, despite
> their shared habitat, the esources utilized were not
> identical as gorillas do not show the tool-use
> technology of chimpanzees. The frequency of
> insect-eating by both species of ape varied seasonally
> and between years but in different ways. This variation
> did not seem to be related to the ratio of fruit to
> foliage in their diets. Gorillas of all age-classes ate
> insects at similar rates. Comparisons with insectivory
> by other populations of gorillas indicate differences
> exist. Mountain gorillas (Gorilla g. beringei) in the
> Virunga Volcanoes, Rwanda, consume thousands of
> invertebrates daily, eating them inadvertently with
> handfuls of herbaceous foods but they deliberately
> ingest insect-foods only rarely. Lowland gorillas at
> Lopé habitually ate social insects, and their selective
> processing of herbaceous foods probably minimizes
> inadvertent consumption of other invertebrates.
> Gorillas at Belinga in northeastern Gabon, 250 km from
> Lop6, ate social insects at similar rates but ignored
> weaver ants in favor of Cubitermes sulcifrons, a small
> species of termite that occurs at Lopé but was not
> eaten by gorillas. This indicates that local traditions
> similar to those reported for chimpanzees also exist
> amongst populations of gorillas.
>
> http://www3.interscience.wiley.com/c...TRY=1&SRETRY=0
'Diet and seasonal changes in sympatric gorillas and chimpanzees
at Kahuzi-Biega National Park
Juichi Yamagiwa1 and Augustin Kanyunyi Basabose2
(1) Laboratory of Human Evolution Studies, Graduate School of
Sciences, Kyoto University, Sakyo, Kyoto 606-8502, Japan
(2) Centre de Recherche en Sciences Naturelles, Lwiro, Bukavu,
Democratic Republic of the Congo
Received: 30 July 2004 Accepted: 22 January 2005 Published
online: 3 September 2005
Abstract Based on 8 years of observations of a group of western
lowland gorillas (Gorilla beringei graueri) and a unit-group of
chimpanzees (Pan troglodytes schweinfurthii) living sympatrically
in the montane forest at Kahuzi-Biega National Park, we compared
their diet and analyzed dietary overlap between them in relation to
fruit phenology. Data on fruit consumption were collected mainly
from fecal samples, and phenology of preferred ape fruits was
estimated by monitoring. Totals of 231 plant foods (116 species)
and 137 plant foods (104 species) were recorded for gorillas and
chimpanzees, respectively. Among these, 38% of gorilla foods
and 64% of chimpanzee foods were eaten by both apes. Fruits
accounted for the largest overlap between them (77% for gorillas
and 59% for chimpanzees). Gorillas consumed more species of
vegetative foods (especially bark) exclusively whereas chimpanzees
consumed more species of fruits and animal foods exclusively.
Although the number of fruit species available in the montane forest
of Kahuzi is much lower than that in lowland forest, the number of
fruit species per chimpanzee fecal sample (average 2.7 species) was
similar to that for chimpanzees in the lowland habitats. By contrast,
the number of fruit species per gorilla fecal sample (average 0.8
species) was much lower than that for gorillas in the lowland habitats.
Fruit consumption by both apes tended to increase during the dry
season when ripe fruits were more abundant in their habitat. However,
the number of fruit species consumed by chimpanzees did not change
according to ripe fruit abundance. The species differences in fruit
consumption may be attributed to the wide ranging of gorillas and
repeated usage of a small range by chimpanzees and/or to avoidance
of inter-specific contact by chimpanzees. The different staple foods
(leaves and bark for gorillas and fig fruits for chimpanzees) characterize
the dietary divergence between them in the montane forest of Kahuzi,
where fruit is usually scarce. Gorillas rarely fed on insects, but
chimpanzees occasionally fed on bees with honey, which possibly
compensate for fruit scarcity. A comparison of dietary overlap
between gorillas and chimpanzees across habitats suggests that
sympatry may not influence dietary overlap in fruit consumed but
may stimulate behavioral divergence to reduce feeding competition
between them.
Keywords Chimpanzee - Diet - Gorilla - Niche divergence - Sympatry
http://www.springerlink.com/content/v074m6375801080w/