Walia Special Edition on the Bale Mountains (2011) - Zoologische ...

Analysis
Data were summarized by habitat and field period. Non-parametric analysis of variance was used
to compare group sizes between habitats and field periods. A Spearman Rank Correlation Analysis
was used to examine the association between group size and altitude.
The program DISTANCE v 2.0 (Laake et al. 1994) was used for estimating mean density and
abundance for the data collected during the second field season; this analysis was not conducted on the
data from the first field season as the number of observations was insufficient. ArcView 3.3 was used
to produce a map of the distribution of the sample sites, observation records and settlement locations.
Results
Population size and attributes
A total of 31 groups of monkeys were observed during the two field periods (Table 2). Monkeys
were always found in groups, with group size ranging from 2 to 20. Group size was skewed, with
several observations of group sizes much larger than the median (5). The range and median group
sizes overlapped between the bamboo and the mixed-bamboo forest for the two field periods.
Table 2. Number of monkeys and group size recorded during the two field seasons.
Habitat December 06-March 07 August 07
Bamboo Forest
Bamboo-Mixed
Forest
N o n - b a m b o o
forest
Total 25 monkeys in 6 groups
Median group size = 4.5 (min =
2, max=6)
Altitudinal range = 2431-3006
Total 23 monkeys in 3 groups
Median group size = 10 (min=2,
max=11)
Altitudinal range = 2365-3178
No monkeys observed Not sampled
Total 107 monkeys in 17 groups
Median group size = 5 (min=2,
max = 17)
Altitudinal range = 2460-3099m
Total 47 animals in 5 groups
Median group size=10 (min=2,
max=20)
Altitudinal range=2315-3051
The surveys were conducted between 7:00-11:30 and 14:00-17:30, when the encounter rate
with monkeys was relatively high. It was not possible to differentiate males and females during the
observations; once spotted, the monkeys quickly flush into dense vegetation that conceals them.
Using the 22 observations from the second field season, the mean density of monkeys was
estimated to be 9.6 individuals/km2 and abundance equal to 1437 individuals (Table 3). However,
the low number of observations and the relatively high estimates of standard error to mean ratio
suggest that these figures should be considered as very preliminary. The information gathered
during the second survey increased the estimate of suitable habitat from 108 km 2 (based on the Dec
06-Jan 07 data) to 149 km 2 (based on the Aug 07 data).
<strong>Walia</strong>-<strong>Special</strong> <strong>Edition</strong> on the Bale Mountains 84