Lake Langano Research Articles

Spatiotemporal lakes surface area changes over 35 years and potential causes in the Central Rift Valley, Ethiopia

Study RegionCentral Rift Valley (CRV) region, Ethiopia. Study FocusThe study aims to investigate the spatiotemporal change in lake water surface extents over 35 years (1986–2020) and identify potential causes. Three alternative multispectral water indices—Normalized Difference Water Index (NDWI), Automatic Water Extraction Index (AWEI), and Modified Normalized Difference Water Index (MNDWI)—derived from Landsat sensors (TM, ETM+, OLI) were utilized to extract and analyze the lake surface area. The Mann-Kendall correlation was applied to examine whether hydro-meteorological and anthropogenic variables are possible causes for changes. New Hydrological Insights for the RegionMNDWI outperforms other indices with over 96 % accuracy in mapping lake surface area. Lake Abiyata experienced the most significant reduction in surface area from 1986 to 2020 (>50 %), followed by Lake Ziway (<2 %) while Lake Langano remained relatively stable. This significant reduction positively correlates to alterations in lake water depth (R2=0.92). Factors such as increased temperature, evaporation, and water abstraction for soda ash production negatively correlated with lake surface area, while inflow from Bulbula River and mean annual rainfall showed positive correlations. Abiyata Lake's decrease in surface area is primarily attributed to water abstraction for soda-ash manufacturing and incoming river flow. If the current trends in water abstraction from the Lake and income water diversion continue, there is a high possibility that Lake Abiyata will change into a terminal lake shortly.

Morphometric Variations of Nile Tilapia (Oreochromis niloticus) (Linnaeus, 1758) (Perciformes, Cichlidae) Collected from Three Rift Valley Lakes in Ethiopia

The pattern of morphometric differentiation among three populations of Tilapia (Oreochromis niloticus) sited in Koka, Ziway, and Langano lakes in the Ethiopian rift valley was examined. Morphometric differentiation was examined, compared and quantified by the use of twelve different body measurements in 391 specimens to generate baseline information for conservation and product improvement plans. The result revealed that comparisons of mean values of morphometric measurements in the three studied tilapia populations statistically significant differences (P&lt;0.05). The Fulton’s condition factor (K) of Oreochromi niloticus samples collected from Lakes Koka, Ziway, and Langano was 1.48, 1.2, and 0.66, respectively. The Discriminant Function Analysis performed on seven variables led to a correct classification in 90.5 % of cases. Differences observed between samples in this study indicated that there is important morphometric variation between the studied tilapia populations. Plotting the two significant canonical discriminant functions separated the Lake Langano population from the other two.

Nutrient-related metabolite profiles explain differences in body composition and size in Nile tilapia (Oreochromis niloticus) from different lakes

This study investigated how metabolite analysis can explain differences in tissue composition and size in fish from different habitats. We, therefore, studied Nile tilapia (Oreochromis niloticus) from three Ethiopian lakes (Gilgel Gibe, Ziway, and Langano) using dried bloodspot (DBS) analysis of carnitine esters and free amino acids. A total of sixty (N = 60) Nile tilapia samples were collected comprising twenty (n = 20) fish from each lake. The proximate composition of the targeted tissues (muscle, skin, gill, gut, and liver) were analyzed. The DBS samples were analyzed for acylcarnitine and free amino acid profiles using quantitative electrospray tandem mass spectrometry. Metabolite ratios were calculated from relevant biochemical pathways that could identify relative changes in nutrient metabolism. The mean weight of Nile tilapia sampled from each lake showed weight variation among the lakes, fish from Lake Ziway were largest (178 g), followed by Gilgel Gibe reservoir (134 g) and Lake Langano (118 g). Fish from Gilgel Gibe showed significantly higher fat composition in all tissues (P < 0.05) except the liver in which no significant variation was observed. The source of fish affected the tissue fat composition. Marked differences were observed in Nile tilapia metabolic activity between the lakes. For instance, the lower body weight and condition of the fish in Lake Langano coincided with several metabolite ratios pointing to a low flow of glucogenic substrate to the citric acid cycle. The low propionyl to acetylcarnitine ratio (C3:C2) in Gilgel Gibe fish is indicating that more of the available acetyl CoA is not led into the citric acid cycle, but instead will be used for fat synthesis. The metabolic markers for lipogenesis and metabolic rate could explain the high-fat concentration in several parts of the body composition of fish from Gilgel Gibe. Our results show that nutrition-related blood metabolite ratios are useful to understand the underlying metabolic events leading to the habitat-dependent differences in the growth of Nile tilapia, and by extension, other species.

The Impact of Lake Ecosystems on Mineral Concentrations in Tissues of Nile Tilapia (Oreochromis niloticus L.).

Simple SummaryFish are a source of minerals that is highly favored by consumers in most parts of the world. However, these minerals become toxic upon high-level intake and can accumulate toxic trace elements in different tissues. Nevertheless, mineral distribution in fish tissues is poorly evaluated. Analyzing tissue mineral distribution would help us to understand the physiological role of each tissue and the impact of the ecosystem on mineral and toxic trace element accumulation in the tissues. We evaluated the differences in mineral and toxic trace element concentrations of Nile tilapia (Oreochromis niloticus) tissues from three aquatic ecosystems. Distinct differences were observed between tissues in Nile tilapia; in addition, these concentrations were substantially affected by the lake the fish were caught from. The accumulation of elements toxic to humans, such as aluminum, should be monitored and, in particular, controlled when rearing these fish in aquaculture. Further investigation is warranted to identify the origin of the very high intestinal Fe concentration in all fish samples, which coincided with high concentrations of Al.This study evaluates the differences in mineral and toxic trace element concentrations of Nile tilapia (Oreochromis niloticus) tissues from three aquatic ecosystems in Ethiopia—Lake Ziway, Lake Langano, and Gilgel Gibe reservoir—with a focus on edible (fillet) and discarded (digestive tract, gills, skin, and liver) parts. A total of sixty (n = 60) Nile tilapia samples were collected, comprising twenty (n = 20) fish from each lake, and analyzed by inductively coupled plasma mass spectrometry. All elements varied markedly among tissues and between the lakes. Some differences in element concentrations were attributed to differences in nutrient load in the ecosystems and the function of the tissues. For instance, the calcium concentrations in skin and gill were distinctly higher in fish from calcium-rich Lake Langano. The d iscarded parts were richer in essential trace elements, showing an opportunity to promote their use in human nutrition to increase the intake of important minerals. However, the accumulation of elements toxic to humans, such as aluminum, should be monitored and, in particular, controlled when rearing these fish in aquaculture.

Analysis of factors affecting farmers` participation in fish production in Lake Langano, Ethiopia

Fishery development is considered as a potential area to enhance income of smallholder farmers in developing countries. In Ethiopia fishing practiced in most freshwater bodies which is a potential strategy for enhancing food security, employment and provide as source of income. Despite the economic importance of fishing at the local level, farm households have paid little attention to the fish production in the study area. Thus, this study was proposed to analyze determinants of farmer’s participation decision on fishing in Langano Lake. The study used the cross-sectional survey to collect primary data from 167 same respondents and mixed research approach. Descriptive statistics, inferential statistics and binary probit model were used to analyze the primary data. The result of analysis indicated that farmer`s’ participation in fish production is significantly determined by various demographic, institutional, social, economic and biophysical factors. To solve the problems and improve the farmer`s participation in fish production,the government and nongovernment organizations, specially district livestock and fishery development office should attempt to hamper factors that hind er participation in fish production and enhance factors that initiates participation in the fishing practice identified in the study.

Morphometric Analysis of Lake Langano Watershed using Geographic Information System

An understanding of watershed characteristics like areal, linear and relief aspect has paramount significance for watershed planning and management. An automatic extraction of these characteristics from digital elevation model is so effective and efficient. The main objective of this research work was Morphometric analysis of Lake Langano watershed characteristics from Digital Elevation model using GIS. This research work employs an automatic extraction of hydrological characteristics using Geographical Information system. The results of finding show that the watershed has highly permeable soil type which absorbs the water passing over the soil. Drainage texture of the watershed is very coarse and the watershed is less affected by erosion. There is high runoff in the watershed due to large number of overland flow length. The shape of the watershed is elongated shape and experiences low peak flow over longer duration of time. Circulatory value of the watershed indicates that lake Langano watershed is not under flood risk. Relief characteristics of the watershed indicate that most part of the watershed is characterized by gentle slope and the peak of south eastern part is characterized by steep slope. Keywords: DEM (digital elevation model), GIS (Geographic Information system), Morphometric analysis, Watershed characteristics. DOI: 10.7176/JEES/10-11-03 Publication date: November 30 th 2020

Tectonics of the Asela‐Langano Margin, Main Ethiopian Rift (East Africa)

AbstractWe provide insights into the tectonics of the Asela‐Langano margin, at the eastern boundary of the central Main Ethiopian Rift, East Africa, by combining field structural data, remote sensing, analysis of the distribution of faults, new dating of faulted material, and analysis of seismicity. The area is characterized by the occurrence of two fault sets: boundary and axial (Wonji) faults, oriented NE‐SW and NNE‐SSW, respectively. Boundary faults show a complex arrangement in the lake Langano area where they display a rhomboidal pattern, due to the presence of NW‐SE‐trending structures, likely related to preexisting transverse fabrics (the so‐called Langano Rhomboidal Fault System). Overall, our analysis supports a structure of the margin characterized by a monocline affected by a series of minor horsts and grabens; this confirms a marked asymmetry of the central Main Ethiopian Rift, with a master fault system on the opposite, western margin. Cumulative paleostress analysis indicates an overall N115°E extension across the Asela‐Langano margin; however, a local variation of the extension direction from axial (Wonji) faults (∼N90°E) to the boundary faults (∼N115°E) can be observed, pointing to a stress reorientation at rift margins. New 14C dating of faulted material and seismicity analysis indicate Late Pleistocene–Holocene and current activity on several normal faults affecting the margin. This suggests that extensional deformation in the central Main Ethiopian Rift is accommodated at the rift margins, with subordinate activity on axial faults, supporting that this rift sector reflects an intermediate stage of rift evolution.

Overview of Length-Weight Relationship, Condition Factor and Size at First Maturity of Nile tilapia Oreochromis niloticus (L.) in Different Water Bodies of Ethiopia: A Review

Length-weight relationship, condition factor and size at first maturity of Nile tilapia Oreochromis niloticus (L.) in different water bodies of Ethiopia have indicated that nearly isometric (b≈3) growth pattern. The Fulton condition factor (K) of O. niloticus was higher in Lake Chamo (2.35) and in Baro River (2.05) than in Gilgel Gibe Reservoir (1.87) and in Lake Langano (1.77). However, it was lowest in Lake Beseka (0.05). Size at first maturity (L 50 ) of O. niloticus was high (42.0 cm TL) for both sexes in Lake Chamo. However, declined in most water bodies of Ethiopia and also exhibits both sexual and seasonal variations. There was variation in size at first maturity with respect to sex in which males had larger size at first maturity than females. Generally, the length-weight relationship, condition factor and size at first maturity of O. niloticus was correlated with availability of food, feeding rate, gonad development, spawning period, water quality parameters can determine the growth rate and the condition of fish and therefore, proper management of this fish stock for conservation and sustainable fishery is critical. Keywords: Condition Factor, Length-weight, Oreochromis niloticus , Size at first maturity, Water bodies of Ethiopia

Early exploration of the Aluto geothermal field, Ethiopia (History of discovery well LA-3)

The Aluto geothermal prospect, located in the Southern part of the Ethiopian Rift valley, hosts two large areas with thermal manifestations (c. 30–40km2 each), one on top of the Aluto volcanic complex with widespread, weak fumarole activity and another thermal area, 10km to the south, discharging thermal waters at the Northern shore of Lake Langano. A project (ETH/78/007) with the Ethiopian Government, EEC, and UNDP, was signed in 1978 supporting further exploration and drilling of deep exploratory wells.The first well (LA-1), with T of 85°C at 1.3km depth, was sited outside the volcanic complex on flat ground, N of Lake Langano. The second well (LA-2), with T of 105°C at 1.4km depth, was located near a fumarole in the W foothills of the Aluto dome. Each well encountered shallow, thermal advective outflows from the Aluto reservoir and impermeable basalts in the bottom section with temperature (T) gradients pointing to an elevated deep heat flux (c. 95–100mW/m2). Rocks from both wells are thermally altered (slight to moderate intensity) and point to mineral alteration T of >150°C (LA-1) and up to 250°C (LA-2). The rocks in the upper 500m exhibit low resistivities of <5Ωm. The palaeo-T structure in LA-2 can be interpreted as a conductive heating- and cooling cycle lasting over a period of c. 0.14Ma using a 1-D analysis.The search for the third well site included the Aluto massif area where resistivity surveys had not found a coherent low resistivity structure in the upper 300m. This led to the exploration of hot ground using >50m drill holes. The intersection of a pattern of hot ground and fault- controlled, NNE trending steam vents was used to site the LA-3 well. It was drilled in 1983 to 2144m depth and encountered 320°C fluids at the bottom – thus becoming the discovery well of the Aluto geothermal project.

Predispersal seed predation on three Vachellia species and one Senegalia species (Fabaceae: Mimosoideae) in the Rift Valley of Ethiopia and Menagesha forest, Ethiopia

AbstractThis study on predispersal seed predation of the leguminous speciesVachellia abyssinica(Hochst. Ex. Benth.) Kyal &amp;amp; Boatwr.,Senegalia senegal(L.) Britton,Vachellia seyal(Del.) P.J.H. Hurter, andVachellia tortilis(Forssk.) Galasso &amp;amp; Banfi was conducted around Lake Langano and Menagesha Forest in Ethiopia to identify the associated seed predators and determine their impact on seed germination. Eight seed beetlesBruchidius albosparsus(Fåhraeus, 1839),B. aurivillii(Blanc, 1889),B. djemensisDecelle 1971,B. discoidalis(Fåhraeus, 1839),B. sinaitus(K. Daniel, 1907),B. silaceus(Fåhraeus, 1839),B. sp 411,B. simulans(Anton and Delobel, 2003), and one unidentified species of Cerambycidae were found associated with seeds of theseAcaciaspecies. These predators damaged less than 9% of seeds of these species, which exhibited lower germination. This study provides unrecorded lists of predispersal seed predators associated with seeds ofVachelliaandSenegaliaspecies in Ethiopia, and some associations are new. There is need to assess the distribution, abundance and effects of predispersal seed predators on otherVachellia, as well as other tree species.

Land Use-Land Cover dynamics of Huluka watershed, Central Rift Valley, Ethiopia

Land Use-Land Cover (LULC) dynamic has of human kind age and is one of the phenomenons which interweave the socio economic and environmental issues in Ethiopia. Huluka watershed is one of the watersheds in Central Rift Valley of Ethiopia which drains to Lake Langano. Few decades ago the stated watershed was covered with dense acacia forest. But, nowadays like other part of Ethiopia, it is experiencing complex dynamics of LULC. The aim of this research was thus to evaluate the LULC dynamics seen in between 1973–2009. This was achieved through collecting qualitative and quantitative data using Geographic Information System (GIS) and Remote Sensing (RS) technique. Field observations, discussion with elders were also employed to validate results from remotely sensed data. Based on the result, eight major dynamic LULC classes were identified from the watershed. Of these LULC classes, only cultivated and open lands had shown continuous and progressive expansion mainly at the expense of grass, shrub and forest lands. The 25% and 0% of cultivated and open land of the watershed in 1973 expanded to 84% and 4% in 2009 respectively while the 29%, 18% and 22% of grass, shrub and forest land of the watershed in 1973 degraded to 3.5%, 4% and 1.5% in 2009 respectively. As a result, land units which had been used for pastoralist before 1973 were identified under mixed agricultural system after 2000. In the end, this study came with a recommendation of an intervention of concerned body to stop the rapid degradation of vegetation on the watershed.

The diatom Thalassiosira faurii (Gasse) Hasle in the Ziway–Shala lakes (Ethiopia) and implications for paleoclimatic reconstructions: Case study of the Glacial–Holocene transition in East Africa

The species Thalassiosira faurii (Gasse) Hasle was found dominating the planktonic diatom community during summer 2012 in Lake Langano which is part of the Ziway–Shala alkaline lake system in Ethiopia. In a previous study, the species had been recorded in high abundance in 13.5–12calka old sediments from the neighbor Lake Abiyata. Using a transfer function for conductivity, peaks in abundance had been interpreted as dry spells at the Pleistocene–Holocene transition since the species was considered strictly halophilous.In this study, a strain of Thalassiosira faurii was isolated from Lake Langano and grown in the laboratory. The observation of its morphology and reproduction, and comparison between modern and fossil populations helped to improve the taxonomic definition of the species. The autecology of the species was also investigated through a salinity tolerance test. The results revealed that the species was much more sensitive to salinity than previously believed. A new conductivity optimum was derived from the experiment and incorporated into the transfer function. The reassessment of lake conductivity variations along the core of Lake Abiyata showed that the intensity of the dry periods preceding the onset of the Holocene had been probably over-estimated.The reconsideration of the species relationship to conductivity may have important consequences for paleoclimatic reconstructions in tropical Africa where Thalassiosira faurii has been reported in abundance. The use of experimentation on local diatom strains allows paleoecologists to solve the problems of low representation of some species in modern dataset and of regional autecological variability within morphotypes.

Analysis of determinants of gross margin income generated through fishing activity to rural households around Lake Ziway and Langano in Ethiopia

This article analyzed determinants of gross margin income from fishing to the rural households around Lake Ziway and Langano in Ethiopia. Four districts adjacent to the two lakes were selected purposively from which 179 respondents drawn randomly. Both primary and secondary information comprises of household structure and assets, climate factors and supportive services were organized. Data analysis employed descriptive statistics, budgetary analysis and the Ricardian method. Budgetary analysis showed positive fish gross margin income (GMI) of ETB 3,023.40 to average fisher. The Ricardian analysis made use of the climate only model (Model 1) and comprehensive model (Model 2). Using Model 1, water level raise due to inflow is vital to earn fair income in addition to the rainfall amount in Season 1, which is supported with positive impact of precipitation water level interaction on fish income. Impact of precipitation was positive in Season 3, due to meher rainfall and withdrawal of fishing labor to join agriculture that minimized over fishing. Using Model 2, precipitation water level interaction has positive impact in Season 2 due to better inflow and Meher rainfall. The interaction term was negative in Season 4 attributed to decreased water level, dry weather and less precipitation. The result also showed positive impact of household members participation, participation in the traditional financial arrangement and capacity to finance operating costs. The study highlights problems facing fishing business like: decreased lake size and water volume, lake turbidity and siltation, open access and weak institutional arrangement to guide fishing efforts, wetland farming and expansion of irrigation to the lake side, cost of fishing materials, minimum sales price as well as poor access to the fish market. Hence, strengthening fishery coperatives, awareness creation, off-farm opportunities, integrated conservation works, reduced wetland farming and acquaintance to social networks were suggested.

Holocene lacustrine fluctuations and deep CO2 degassing in the northeastern Lake Langano Basin (Main Ethiopian Rift)

This work reports the results of an integrated investigation on Holocene faulted deposits exposed on the northeastern Lake Langano in the central sector of the Main Ethiopian Rift (MER). The Lake Langano is part of a closed basin and thus it is highly sensitive to climate fluctuations. The present study explored the foot of the Haroresa escarpment, where coarse-grained slope deposits interbedded with thin lake shore shell-rich coarse sands are well exposed. Stratigraphical analysis of these deposits, integrated with radiocarbon dating carried out on lacustrine gastropod Melanoides tubercolata shells, points to significant lake level fluctuations forced mainly by climate oscillations. These have been interplaying during the early and middle Holocene with a structurally-controlled threshold separating an embayment of the Lake Langano to the south, from the small perched Lake Haro Bu-a basin to the north. Significant differences in the 13C/12C isotopic ratio have been identified in the M. tubercolata shells collected on the opposite sides of such a threshold. The time-space variations of the isotopic signature of the shells are referred to the mutual relationships between the two main different CO2 sources (i.e., microbial activity and deep mantle degassing) dissolved in the lake water.

Prevalence of intestinal parasites among school children in a rural area close to the southeast of Lake Langano, Ethiopia

Abstract Background: Epidemiological information on the prevalence of various intestinal parasitic infections in different regions/localities is a prerequisite to develop appropriate control strategies. Objective: The aim of this study was to determine the prevalence of intestinal parasitic infections in schoolchildren found in a rural area close to the southeast of Lake Langano. Methods: In April 2003, fresh stool samples were collected from 259 students enrolled in two primary schools located in southeast of Lake Langano. The samples were processed using both Kato and formol-ether concentration methods and then microscopically examined for intestinal parasitic infections. A finger prick blood sample was also collected and haematocrit determined for each individual. Results: Of the 259 students surveyed for intestinal parasites, 217(83.8%) had one or more parasites. Prevalence of hookworm was the highest (60.2%), followed by Schistosoma mansoni (21.2%), Trichuris trichuria (14.7%), Taenia spp. (13.9%), Entamoeba histolytica/dispar (12.7%), Ascaris lumbricoides (6.2%), Giardia duodenalis (6.2%) and Strongyloides stercoralis (5.8%), in that order. An association was not found between hookworm infection and low haematocrit value of the study subjects. Conclusion: The occurrence of various intestinal parasitic infections and high prevalence of hookworm infection among schoolchildren in southeast of Lake Langano calls for institution of intervention measures. [Ethiop.J.Health Dev. 2004;18(2)116-120]

AMS-14C Chronology of a Lacustrine Sequence from Lake Langano (Main Ethiopian Rift): Correction and Validation Steps in Relation with Volcanism, Lake Water and Carbon Balances

Located in the Ziway-Shala Basin of the Main Ethiopian Rift, Lake Langano is part of an asymmetric half-graben, defined by a series of north-northeast-trending faults in the tectonically active zone of the rift. A 15-m deep succession of organic homogeneous muds, silts, bioclastic sands, and pyroclastic layers was cored in 1994. The definition of a certified radiocarbon chronology on these deposits required the indispensable establishment of modern hydrological and geochemical balances. The isotopic contents of the total dissolved inorganic carbon (TDIC) of surface water clearly show the influence of a deep CO2 rising along the main fault crossing the lake basin. The 5.8 pMC disequilibrium existing in 1994 with the atmosphere likely produces the aging of authigenic materials developing at the lake surface. However, with a mean residence time of ~15 years, this apparent 14C aging of Lake Langano water still integrates the 14C produced by the nuclear tests in the 1960s. Reconstructing the natural 14C activity of the lake TDIC allows for the quantification of the deep CO2 influence, and for the correction of AMS-14C datings performed along the core. The correction of the AMS-14C chronology defined on Lake Langano allows for a better understanding of paleohydrological changes at a regional scale for at least the last 12,700 cal BP.

Implication of Papio anubis in the transmission of intestinal schistosomiasis in three new foci in Kime area, Ethiopia

Epidemiological studies were conducted in the Lake Langano area in the Rift Valley of Ethiopia to determine the occurrence of schistosomiasis and assess factors involved in its transmission. Microscopic examination of faecal specimens from free ranging Papio anubis (anubis baboon) troops from Bishan Gari and Burka Dita forest reserves revealed Schistosoma mansoni eggs with a prevalence of 12.1% (11/91) and 26.2%(34/130), respectively. The eggs were viable as confirmed by miracidial hatching and infectivity tests. Out of the total 12 communities (three schools, five villages and one herdsmen community) surveyed for schistosomiasis around Lake Langano, individuals excreting S. mansoni eggs were found in nine communities with prevalence of infection ranging from 1.4 to 43%. The intensity of infection ranged from 24 EPG (eggs per gram of faeces) to 243 EPG. Excretion of viable eggs by the baboons indicate that they play a role in maintenance of S. mansoni infection in the locality. The detection of S. mansoni eggs in young children, collection of cercarial-infected Biomphalaria pfeifferi in water bodies, and establishment of S. mansoni infection in lab-bred mice have confirmed establishment of transmission foci in Kime area, south-east of Lake Langano. However, the lake itself does not seem to support transmission of schistosomiasis since no snails were found along the shore of the Lake. Further investigations are indicated to fully elucidate the role baboons play in the epidemiology of schistosomiasis in the Rift Valley of Ethiopia. The risk of introduction of water-based development projects in these new endemic foci in relation to S. mansoni infection in the baboons is discussed.

A NEW SPECIES OF TOAD FROM THE RIFT VALLEY OF ETHIOPIA, WITH OBSERVATIONS ON THE OTHER SPECIES OF BUFO (AMPHIBIA ANURA BUFONIDAE) RECORDED FROM THIS COUNTRY

SUMMARY A new species, Bufo langanoensis, is described from Lake Langano in the Rift Valley of Ethiopia. The species is acoustically and morphologically rather similar to B. blanfordi Boulenger, 1882 and to an undescribed form (sp. A), and the three are believed to form a B. blanfordi species group within the B. regularis complex. B. langanoensis is known to be strictly sympatric only with B. regularis Reuss, 1834, although its ecological requirements seem to be similar to those of three other species which occur in Ethiopia (B. garmani Meek, 1897, B. xeros Tandy et al., 1976 and B. maculatus Hallowell, 1854). However, the new species differs acoustically and morphologically both from these species and from 20 other members of the genus Bufo with which it has been compared, including all those which are known to occur in Ethiopia. The most distinctive morphological features of B. langanoensis are the very full webbing between the toes, extensive development of spinules, rather obscure dorsal colour patter...

Birds of a Euphorbia-Acacia Woodland in Ethiopia: Habitat and Seasonal Changes

The objective of this study was to understand better the dynamics of a species-rich tropical bird community. This paper reports the analysis of the habitat and the seasonal trends, and a later paper will give a detailed account of the species recorded. Reviews of data on breeding seasons in the tropics have been published by Baker (1939), who discussed general trends, by Skutch (1950) for Central America, Snow & Snow (1964) for northern South America, Moreau (1950, 1966) for Africa generally, Benson (1963) and Winterbottom (1963) for southern Africa, Voous (1950) for Indonesia, Betts (1952) for southern India, Keast (1959) and Frith & Davis (1961) for Australia. These compilations utilize data over large areas. Several detailed accounts of local areas are also relevant to this study, such as those of Davis (1945) in Brazil, Davis (1953) in Guyana, Miller (1963) in Colombia and Snow & Snow (1964) in Trinidad. The possible role of staggered nesting as a factor in species diversity of tropical habitats has been discussed by MacArthur (1964) and by Ricklefs (1966), both of whom concluded that the staggering had little influence on diversity. The study area, 100 x 200 m (2 ha = 4 94 ac), was located in the Main Ethiopian Rift, 9 km south of Lake Langano, and 27 km north-north-east of the town Shashamanne. The substrate is lacustrine sediments and the terrain is very flat. Because it is located on the upper side of a small Tertiary fault line, about 1 km north, the lacustrine layer is much shallower than over most of the Rift floor. The underlying volcanic bedrock averages about 2-3 m below the soil surface. The soil is an alkaline (pH = 7 6-8.2), silty, clay loam, fairly rich in nutrients. The elevation is 1800 m. The climate of this area is not documented, but Fig. 1 shows the monthly rainfall averages for Shashamanne. Although only 27 km away and only 100 m higher in elevation, the town is located on one of the higher points of the Rift floor and is exposed to the moisture-laden south-west winds of the rainy season, whereas the study area is in a rain shadow behind the Shashamanne area. The town is on the border of the Podocarpus gracilior Pilger forest zone, while the study area is in a thorn woodland. The rainfall pattern shown in Fig. 1 is the same as that for my study area, but the average rainfall is undoubtedly less than 50 cm, instead of the 83 cm at Shashamanne. There are early rains in April, usually a short dry spell in late May and early June, and then more extended rains until October.