Gorillas in the Odzala National Park
As part of the European program ECOFAC
(Conservation et utilisation rationelle des Ecosystèmes Forestiers
en Afrique Centrale), a study of the large mammal populations frequenting
the swampy clearings of the Odzala National Park, Republic of Congo, was
conducted over a period of 10 months. This study has especially focused
on gorillas that visit the Maya Nord clearing, located 10 km north of
the park boundaries. The exceptionally good visibility has permitted an
accurate determination of group composition and population structure.
In Maya Nord, gorillas were present for 88% of the 132 observation days.
A total of 398 hours of direct observation have been carried out. Altogether
217 group visits and 224 solitary visits have been recorded, corresponding
to a total of 2,637 gorilla visits. 442 gorillas have been identified
including 37 groups and 21 lone gorillas.
The gorilla density has been estimated at 10 individuals/kmē. Groups include
only one silverback male and have a mean size of 11.7 individuals (range
2-29), which is larger than what has already been described for western
gorillas. The mean number of infants per female (0.63) characterises a
high birth rate. Infants, juveniles and subadults represent 56% of the
population. The equal contribution of the three non-adult classes, about
20% each, confirms the good survival of young, especially during the passages
from infant to juvenile and from juvenile to subadult.
Swampy clearings are especially attractive to gorillas that devote about
66% of their presence time to feeding on 4 herbaceous plant species. Sample
analyses have shown that plants in clearings were richer in mineral salts
than those in forests.
Several groups and/or lone individuals may visit the area simultaneously
and 55% of the visits have led to inter-group encounters. In general,
groups and/or solitary individuals ignore each other and only 29% of such
encounters have led to agonistic interactions. Peaceful approaches (23%
of intergroup encounters) and group mixings (6%) were observed. In spite
of food selectivity and the patchy distribution of preferred plants, resource
abundance seems to permit peaceful coexistence.
Abundance of Marantaceae in the forest and mineral-rich places in marshy
clearings allows the Maya Nord region to house a large population of gorillas.
Minerals may play an important role in the high birth rate and survival
of offspring. The long-term survival of this population seems secured
under the present conditions of the park which currently has no timber
harvesting, low human presence and very low levels of poaching.
Unfortunately, human pressure is still increasing in the areas close to
the park. This highlights the value of the current ECOFAC conservation
program which focuses on western lowland gorillas together with other
key species, such as forest elephants which inhabit the Maya Nord region.
It encourages support of the park extension project to include this area,
rich in numerous salt clearings and still spared by logging. The extension
of the park would provide a sufficient area to assure the survival of
large mammal populations such as elephants. It would also permit connections
with other protected regions. The ECOFAC leaders still have to convince
the authorities that the development of the park will provide financial
resources to the local human populations. The park's financial autonomy
is one of the main objectives of the ECOFAC program, and the development
of ecotourism, facilitated by the exceptional conditions of observation,
is considered a promising way of attaining it. Unfortunately, the current
political conditions make the reinforcement of the protected areas difficult
and the park extension project has been postponed.
Florence Magliocca
Florence Magliocca is presently finishing her dissertation. She works with Annie Gautier-Hion at the University of Rennes. In particular, she has studied gorillas, elephants, buffaloes, sitatungas, giant forest hogs and red river hogs in the Maya Nord clearing.
