ABSTRACTS FOR 2004
Ecology of L’Hoest Monkey (Cercopithecus l’hoesti Sclater, 1899) in Kalinzu
Forest
Reserve, South Western Uganda
By
Casim Umba Tolo
2004
Supervisor
Prof. Jonathan Baranga (PhD), Department of Biology, MUST
Abstract
Ecology of L’Hoest Monkey (Cercopithecus l’hoesti Sclater, 1899) was studied in
Kalinzu Forest Reserve, south Western Uganda. The study was carried out starting in
October 2003 to September 2004. The following were investigated: population density
and distribution, diurnal activity patterns, activity budgets, activity frequency in relation
to tree height, dietary selection, group ranging patterns and group spread of L’Hoest
Monkeys in the study area. Census and scan sampling methods were used in data
collection.
Population censuses of L’Hoest Monkeys were conducted along 10 line transects running
east to west in the study area. Each transect was 5 km long with an average width of
71.96m. The distance between one transect and the next is 500m. Censuses were
conducted only animals were encountered while walking on a transect between 0730 and
1730 hours. Each line transect walked at least twice every month of the study period. A
total of 28 censuses were completed per transect during 12 months of the study. Scan
samples (Altmann, 1974) of activities of L’Hoest Monkeys were conducted at five
minutes intervals from dawn to dusk (0630-1830), six times a week for 12 consecutive
months. Scan samples conducted on single individuals referred to as “focal animals”
from different age groups, changed on daily basis. During the scan samples, feeding,
foraging, moving, grooming, resting, vocalization and other activities were recorded in a
priorly prepared data sheet.
A total of 1,017 L’Hoest Monkeys were counted in the study area with an average troop
size varying between 25-32 individuals around the saw mill (middle of the study area)
while those found at the periphery ranged between 7-10 individuals. Age-class of the
population gave adult male: adult female: juvenile: infant as 9: 18: 9: 1 respectively. Due
to unequal distribution of food plants, overall 54 % (n = 534) of the total L’Hoest
Monkey population occurred in the eastern block of the study area and only 46% (n =
455) existed in the western side. Variation in mean monthly population was statistically
significant across months of the year. A cross tabulation between the mean monthly
population in months of March and September show significant variation ( 2 =10.000,
df
= 3, P = 0.019). L’Hoest Monkey population density in the study area was found to be 27
animals / km2 (using maximum perpendicular distance from transect to animal).
28
Mean monthly diurnal activity patterns generally showed seasonal variations with the
activity frequency peaking at the months of January – February dry season and the
second peak occurring at the months of June – July dry season. Moving was the most
prevalent activity across all age groups throughout the year, followed by feeding;
grooming and foraging being the least. However, variations between activities of
individuals of particular age group, for a given activity were insignificant. The mean
activity budget for the four age groups over the study period shows moving in 29.17% of
records being the highest and the least was ‘other’ activities (1.59%). Activities generally
show two peaks across all the four age groups within the same group throughout the day.
The first peak occurs at around mid morning (0930 – 1130 hr) and the second peak
towards late afternoon (1330 – 1530 hr).
The study found the activity frequency in relation to tree height was such that the species
rarely utilizes heights above 6.0 m; rather most activities occur at heights less than 0.5m
above ground level; hence a semi-terrestrial primate. No significant difference in dietary
selection in different age groups exists in L’Hoest Monkeys. However, significantly high
percentage of their diet is composed of food plants as compared to arthropods except for
infants; adult female (56% food plants: 44% arthropods), adult male (55% food plants:
45% arthropods), Juvenile (51% food plants: 49% arthropods) and infant (47% food
plants: 53% arthropods) respectively. For the purpose of this study, a group has been
assigned four relative age classes as adult male and adult female (estimated to be more
than 5 years old), juvenile (1 – 5 years old) and infant (less than 1 year old).
Patterns of group ranging showed that groups altered their ranging patterns in response to
changes in seasons, demonstrating an overall tendency towards long- distance ranging in
dry months of the study period and vice-versa, possibly due to changes in food regimes in
their habitat. On the other hand, mean monthly home range area of the L’Hoest Monkey
group based on the grid-cell analysis in the study area was 27.78 ha. Group spread among
the troop members was highly significant in the course of the day at different time block
of morning (0630 - 1000), mid morning (1000 - 1200), afternoon (1200-1600) and
evening (1600-1830) hours compared at 5.0m intervals (P = 0.014), except at a distance
range between 30.0m – 34.9m where it was insignificant ( =8.309, df = 3, P = 0.056).
28
Mean monthly diurnal activity patterns generally showed seasonal variations with the
activity frequency peaking at the months of January – February dry season and the
second peak occurring at the months of June – July dry season. Moving was the most
prevalent activity across all age groups throughout the year, followed by feeding;
grooming and foraging being the least. However, variations between activities of
individuals of particular age group, for a given activity were insignificant. The mean
activity budget for the four age groups over the study period shows moving in 29.17% of
records being the highest and the least was ‘other’ activities (1.59%). Activities generally
show two peaks across all the four age groups within the same group throughout the day.
The first peak occurs at around mid morning (0930 – 1130 hr) and the second peak
towards late afternoon (1330 – 1530 hr).
The study found the activity frequency in relation to tree height was such that the species
rarely utilizes heights above 6.0 m; rather most activities occur at heights less than 0.5m
above ground level; hence a semi-terrestrial primate. No significant difference in dietary
selection in different age groups exists in L’Hoest Monkeys. However, significantly high
percentage of their diet is composed of food plants as compared to arthropods except for
infants; adult female (56% food plants: 44% arthropods), adult male (55% food plants:
45% arthropods), Juvenile (51% food plants: 49% arthropods) and infant (47% food
plants: 53% arthropods) respectively. For the purpose of this study, a group has been
assigned four relative age classes as adult male and adult female (estimated to be more
than 5 years old), juvenile (1 – 5 years old) and infant (less than 1 year old).
Patterns of group ranging showed that groups altered their ranging patterns in response to
changes in seasons, demonstrating an overall tendency towards long- distance ranging in
dry months of the study period and vice-versa, possibly due to changes in food regimes in
their habitat. On the other hand, mean monthly home range area of the L’Hoest Monkey
group based on the grid-cell analysis in the study area was 27.78 ha. Group spread among
the troop members was highly significant in the course of the day at different time block
of morning (0630 - 1000), mid morning (1000 - 1200), afternoon (1200-1600) and
evening (1600-1830) hours compared at 5.0m intervals (P = 0.014), except at a distance
range between 30.0m – 34.9m where it was insignificant ( 2 =8.309, df = 3, P = 0.056)