Distribution of the Bale monkey (Chlorocebus djamdjamensis) in the Bale Mountains and its Ecology in the Odobullu Forest, Ethiopia – A Study of Habitat Preference, Population Size, Feeding Behaviour, Activity and Ranging Patterns
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Date
2008-07
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Addis Ababa University
Abstract
The Bale monkey (Chlorocebus djamdjamensis) is endemic to Ethiopia. Bale
monkeys are recorded as Data Deficient in the IUCN Red List of Threatened
species categories. This study was conducted from August 2007 to May 2008 to
determine the habitat preference, population size, feeding ecology, activity and
ranging patterns of the Bale monkey in the Odobullu Forest and distribution
pattern across the Bale Mountains, Ethiopia. A total of 136 censuses of 1.8 to 3.2
km transects were conducted with a cumulative distance of 302.4 km in three
different habitat types. A total of 62 Bale monkey groups were sighted and all of
the encounters were observed in the bamboo forest habitat. In addition, the two
study groups spent all group scan time exclusively in the bamboo forest habitat
irrespective of seasons. Thus, Bale monkeys could be considered as bamboo
forest specialists. The average group encounter rate of the monkeys in the
bamboo forest was 0.44 per km and the average density was 124.69 per km2.
The total population of Bale monkeys in the Odobullu bamboo forest is estimated
to be 1746 individuals. The distribution of Bale monkeys in the Odobullu Forest
was interlinked with bamboo forest habitat. The presence or absence of Bale
monkeys in the bamboo forest habitat with altitude between 2400-3250 m asl
was surveyed in the Bale Massif and three new Bale monkey populations were
discovered. The activity pattern, feeding ecology and ranging behaviour were
studied in two neighbouring groups with 15 minutes interval scan sampling for
eight month study period. Feeding comprises the majority of their activity time
with 65.7% followed by moving and resting that comprises 14.4% and 10.7%,
respectively. Bale monkeys spent 7.1% of their time for social and the remaining
2.4% for other activities. The overall diet composition of Bale monkeys was
dominated by young leaves, contributing 80.2%. In addition, they feed on fruits
(9.6%), flowers (3.1%), animal preys (2.3%), shoots (1.5%), stems (1.4%),
mature leaves (1.1%) and roots (0.9%). Bale monkeys consumed a total of 11
plant species, of these, the top five accounted 94.3% of their overall diet. Of
these, bamboo (Arundinaria alpina) contributed 76.7% of their overall diet, of
which 73% was from young leaves. The mean daily range length for the study
groups was 928 m and the average yearly home range size of the study groups
was 15.2 ha. The narrow ecological niche of the species may be a threat for its
survival due to the bamboo harvest by local people for commercial purposes.
The population status and distribution pattern of the Bale monkeys has to be
studied in the neighbouring Bale Mountains Massif as well. Results from such
future studies combined with these obtained in the present study could contribute
in preparing proper management and conservation plans for the Bale monkeys.
Thus, appropriate management action should be taken to conserve the species
and their most important food resources, bamboo.
Key words: Bale monkey, diet, distribution, Ethiopia, habitat preference,
home range, Odobullu Forest, population size
Description
Keywords
Bale monkey, diet, distribution, Ethiopia, habitat preference, home range, Odobullu Forest, population size