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Anteneh Shimelis ¹, Afework Bekele ¹, Simon Thirgood ²

Affiliations
1 Department of Zoological Sciences, College of Natural Sciences, Addis Ababa University, Addis Ababa, ET
2 Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, GB

Abstract

The main objective of this paper is explaining the spatial dynamics of rodent population in the Afro-alpine moorlands of the Bale Mountains National Park (BMNP). While assessing patterns of rodent abundance, species-specific relationships of abundance with habitat features were evaluated. The habitat variables were percent cover of vegetation and other structural features of the environment. The importance of habitat variables in explaining species-specific patterns in abundance was evaluated using regression modelling. The models were also used to make predictions and corroborate predictions. Percent cover of Alchemilla herbs came out to be the only habitat feature with significant contribution to the predictive value of each model built separately for Arvicanthis blicki, Lophuromys melanonyx and Stenocephalemys albocaudata. Each model then was used to produce estimates of abundance of each species using habitat data collected in 2007 and 2008. The resulting estimates correlated at high statistical significance with what was observed on the ground in both the years.

Keywords

Afro-Alpine Moorlands, Abundance, Rodents, Spatial Dynamics.

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Anteneh Shimelis ¹, Afework Bekele ¹, Simon Thirgood ²

Affiliations
1 Department of Zoological Sciences, College of Natural Sciences, Addis Ababa University, Addis Ababa, ET
2 Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, GB

Abstract

Indicator species may provide useful substitute for large scale surveys to monitor biodiversity. We conducted surveys in the Afro-alpine habitats of the Bale Mountains National Park (BMNP) with the objective of identifying indicators for the species richness of the raptor guild. Raptors were counted by scan sampling technique from a suitable vintage point. Three classes of 18 sample units grouped according to the variability of the moorland ecosystem in the magnitude of process variables important for raptor species richness were used in determining the indicator value of species as a function of their abundance concentration and the percentage of species occurrence per sample group. This procedure determined indicator values for all species in the resident raptor community. Comparison with randomly expected values demonstrated that only Aquila verreauxii and A. chrysaetos have indicator values that were significantly larger than the randomly expected values. The species richness estimated using the abundances of these two species predicted the observed species richness of the whole community in a linear regression model that explained 66% of the deviance in the data set. Furthermore, the species richness of the community predicted by process variables had correlation of very high significance with that predicted by the indicator species. We have thus identified two indicator species to a raptor guild of the BMNP and demonstrated that these two species encapsulated most of the information regarding the species richness response of the guild to key process variables in the Afro-alpine moorland ecosystem. Our findings contribute significantly to current and future efforts of monitoring the biodiversity of the park providing a cheap and quick means of data generation relevant for making management decisions.

Keywords

Raptor Guild, Species Richness, Indicator Species.

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Anteneh Shimelis ¹, Ermias Addmasu ², Afework Bekele ², Stuart Williams ³, Simon Thirgood ⁴

Affiliations
1 Department of Biology, Addis Ababa University, ET
2 Addis Ababa, Semen Mazegaja, ET
3 Fauna and Flora International, Cambridge, GB
4 Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, GB

Abstract

The Afro-alpine moorlands of the Bale Mountains National Park (BMNP) constitute a diverse guild of avian carnivores. The response of the species richness of this guild to ecological processes is evaluated in this paper. Importance of elevation, topographic physical features, patch heterogeneity of habitat and prey were evaluated in explaining the species richness of the guild of diurnal raptors. The spatial variation in the moorland ecosystem as result of associations of these explanatory process variables was determined through a Principal Component Analysis. This showed there were three spatial clusters of census patches that held significantly different number of species of the guild. Importance of the variables that defined the spatial variability of the ecosystem in explaining the changes in the species richness of the raptor guild was explored through simple correlation analyses and step-wise multiple linear regression that made use of PCA components of covarying explanatory variables. The first axes of the PCA mainly defined by elevation, patch physical features, habitat heterogeneity, diversity of relatively small birds and relatively large sized avian and mammalian prey was selected as a significant predictor. In this model, species richness responded negatively to the environmental variables. Heterogeneity of patches in vegetation type and species richness of prey communities that included birds and mammals such as hare and hyrax affected the species richness of the raptors significantly positively. A simple linear regression model showed interspecific niche overlap declined as a function of species richness.

Keywords

Bale Mountains National Park, Raptor Guild, Species Richness, Afro-Alpine Moorlands.

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Anteneh Shimelis ¹, Afework Bekele ¹, Simon Thirgood ²

Affiliations
1 Addis Ababa University, Department of Biology, ET
2 Macaulay Institute, Craigiebuckler, Aberdeen, AB15 8QH, GB

Abstract

Quantifying diet related responses of species is key for understanding their functional relationship with their environment. Variation in its magnitude reflects differences in the adaptive value of spatial locations within the distributional range of a species. Amongst the key factors that may account for such variation, differences in prey abundance are critical particularly for predatory species. In this paper, the relationship of the use of patches for foraging by B. augur with prey abundance in the Afro-alpine habitats of the BMNP was studied. Data on the frequency of usage of patches for foraging by B. augur and the abundance of suitable prey species was collected by having samples at three contrasting areas that reflect the overall variation in the Afro-alpine system. Classification of patches using prey abundance predicted their group membership along with the intensity of foraging by B. augur, which varied with very high significance. Two latent variates that were computed by linearly combining the abundance of prey species explained significantly B. augur's foraging frequency significantly in a quadratic and linear regression models. The first variate that explained most of the group variation in prey abundance predicted the frequency of foraging by B. augur significantly in a quadratic model that explained 66 % of the variation. This variate was mainly defined by the abundances of A. blicki, L. melanonyx and O. bottae. The second variate with a smaller proportion of group variation contributed significantly to the predictive value of a linear regression model that explained 77 % of the variation in the data set. The discriminant scores of this variate were mainly contributed by A. blicki and S. albocaudata. Interpretation of our results indicated that A. bilicki along with S. albocaudata and L. melanonyx may have played principal role in affecting B. augur's foraging decisions across patches. Generally, in this paper we determined the main prey species that affect the foraging behaviour of B. augur for the first time and presented a body of information and interpretation essentially laying the foundation for further understanding of the species ecology in the BMNP and also in Ethiopia. The findings also assist the general conservation effort in the NP and also initiatives that may specifically target B. augur.

Keywords

Bale Mountains National Park, Buteo augur, Foraging Behaviour, Functional Relationship, Prey Abundance.

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Anteneh Shimelis ¹, Mitchell Pinard ², Addisu Asefa ³

Affiliations
1 Addis Ababa, ET
2 University of Aberdeen, Scotland, GB
3 Bale Mountains National Park, Robe, ET

Abstract

Human simplification of habitat in the Harenna forest mainly happens by permanently removing woody vegetation. We evaluated the impact of such simplification of habitat on bird species richness. Birds were counted using the point count method at points that were laid out along transect lines, and from their presence/absence, species richness was worked out. By establishing 50m by 50m quadrats at bird counting stations, we counted the number of basal remnants of cut trees and we measured vegetation structure variables such as % grass, % other herbs, % shrubs, % bush and % canopy (tree cover). Tree, bush and shrub covers did have significant positive correlation with bird species richness. As the magnitude of tree cutting increased species richness of birds declined significantly. Similarly with bird species richness, structural variables such as tree, bush and shrub covers did have significant negative correlation with the tree cutting variable. Due to this, we carried out Principal Component Analysis and the first component that was influenced mainly by tree cover and tree cutting variables significantly explained 84.7 % of the variation in bird species richness in a stepwise multiple regression analysis. Bush and shrub cover did also have significant positive contributions towards the explanatory value of the first component, thus, their positive contribution in explaining bird species richness is noteworthy. Results showed habitat simplification through tree cutting has significant negative impact on bird species richness.

Keywords

Bird Species Richness, Habitat Structure, Habitat Simplification, Harena Forest, Tree Cutting.

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