bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feeding‐height stratification among African browsing ruminants
Authors: DUTOIT J.T. 
Published: April 2008

SummaryThis study investigated the hypothesis that the use of different feeding levels in the vegetation promotes resource partitioning among browsing ungulate species in African savannas. Focal animal feeding observations, recorded on a real‐time basis using a computerized data‐capture system, were conducted on giraffe (Giraffa camelopardalis Linnaeus), kudu (Trageluphus strepsiceros Pallas), impala (Aepyceros melampus Lichtenstein) and steenbok (Raphicerus campestris Thunberg) in the central region of the Kruger National Park, South Africa. Although there was clear stratification in mean feeding heights among the four species throughout the seasonal cycle, there was considerable overlap in the feeding‐height ranges of kudu, impala and steenbok. Hence, feeding‐height stratification probably only separates giraffe from the other species. Giraffe bulls fed at a higher level in the vegetation than cows, often with head and neck extended vertically. It is suggested that bulls benefit in this by gaining access to nutritious new shoots in the upper canopy, but may suffer an increased predation cost due to reduced vigilance when in this posture.RésuméCette étude a voulu vérifier l'hypothèse selon laquelle l'usage, à des fins alimentaires, de différents étages de la végétation favorise le partage des ressources entre les espèes d'ongulés brouteurs des savanes africaines. On a fait des observations d'animaux doisis en train de se nourrir, enregistrées en temps réel à I'aide d'un système informatisé de recueil de données, sur la girafe (Giraffa camelopardalis Linnaeus), le koudou (Trageluphus strepsiceros Pallas), I'impala (Aepyceros melumpus Lichtenstein) et le steenbok (Raphicerus campestris Thunberg), dans la région centrale du Parc National Kruger, en Afrique du Sud. S'il existait une nette stratification des hauteurs moyennes auxquelles les quatre espéces s'alimentaient tout au long du cycle saisonnier, il y avait un recouvrement considérable des niveaux alimentaires des koudou, impala et steenbok. On peut donc dire que les stratifications des étages alimentaires ne séparent probablement que les girafes des autres espèces. Les girafes mâles mangent une végétation plus haute que les femelles souvent avec le cou et la tête tendus verticalement. On suggère que l'avantage qu'ils en tirent ainsi est d'accéder aux jeunes pousses nourrissantes de la canopée mais ils sont d'autre part plus touchés par la prédation du fait que, dans cette position, leur vigilance est amoindrie.
Observations on the benthos of Murchison Bay, Lake Victoria, East Africa
Authors: OKEDI J.Y. 
Published: April 2008

SummaryThere is paucity of data on benthic organisms in Lake Victoria, as in many other African lakes. A study to ascertain the biomass, standing crop and spatial distribution of benthic organisms in the northern shores of Lake Victoria indicated a rich benthic fauna composed mainly of insects, molluscs and oligochaetes. Total biomass for the 200 km2 Murchison Bay was 146,000 tonnes. The lamellibranchs formed the highest biomass (68,940t) followed by gastropods (30,840t), insects (25,760 t) and annelids (20,460 t). Mean standing crop biomass values for genera in the various taxa were determined from their spatial distribution patterns (mean numbers per unit area) and mean individual weights. The high benthic biomass is currently under‐utilized by benthic organisms at higher trophic levels and consequently represents utilizable organic matter directly or indirectly for man's benefit. Hence, a lakewide study is recommended.RésuméOn possède peu de données sur les organismes benthiques du lac Victoria come de beaucoup d'autres lacs africains. Menée dans le but de connaître la biomasse, l'inventaire et la distribution spatiale des organismes benthiques sur les bords nord du lac Victoria, une étude a révélé une faune benthique riche, composée principalement d'insectes, de mollusques et d'oligochétes. La biomasse totale pour les 200 km2 de la Murchison Bay était de 146,000 tonnes. Les lamellibranches en composaient la plus grande part (68,940 t), suivis par les gastéropodes (30,840t), les insectes (25,760t) et les annelides (20,460t). Les valeurs moyennes de biomasse par genre des différents taxons ont été déterminées à partir du schéma de leur distribution spatiale (nombres moyens par unité de surface) et du poids individuel moyen. La biomasse benthique élevée est actuellement sous‐utilisée par les organismes benthiques des ordres trophiques supérieurs et représente par conséquent une matière organique directement ou indirectement utilisable au profit de l'homme. On recommande donc une étude à l'échelle du lac entier.
Vegetation of channels of the northeastern Okavango Delta, Botswana
Authors: ELLERY W. N. , ELLERY K. , ROGERS K. H. , McCARTHY T. S. , WALKER B.H. 
Published: April 2008

SummaryPlant assemblages rooted within channels, as well as in peat deposits flanking channels, in the northeastern Okavango Delta have been classified and their distribution related to environmental conditions. Within‐channel assemblages appeared to be related to the introduction of sediments from source areas and to differences in channel dimensions (particularly water depth) and current velocity. Channel margin assemblages appeared to be related to seasonal and longer‐term water level fluctuations, as well as the extent to which water, introduced from either the catchment or from local rainfall, contributed to the water budget. These two classifications have been combined in a functionally based classification of channels in the study area in which five channel types were recognized; long‐term and short‐term aggradational, primary filter and confined and unconfined outlet channels. Comparison of these channel types with an earlier classification by Wilson (1973) has indicated some degree of correspondence. A number of changes in the spatial distribution of similar channel types have, however, taken place since the earlier study, mainly in the upper reaches of the study area. The reasons for these and possible short‐term future change have been inferred based on the findings in the present study.RésuméLes groupements de plantes enracinées dans les chenaux ainsi que dans les dépôts de tourbe bordant les chenaux dans le nord‐est du delta de l'Okavango ont été classés et leur distribution a été mise en rapport avec les conditions du milieu. Les groupements à l'intérieur des chenaux semblent être liés a l'introduction de sédiments provenant de la zone des sources et aux différences de dimension des chenaux (en particulier la profondeur de l'eau) et à la vitesse du courant. Les groupements des rives des chenaux semblent être liés aux fluctuations tout saisonnières qu'à plus long terme du niveau d'eau, de même qu'à la mesure dans laquelle l'eau—qu'elle provienne du bassin hydrographique ou des chutes de pluies—contribue au bilan hydrique. Ces deux classifications ont été combinées en une seule classification fonctionnelle basée sur les cinq types de chenaux identifiés dans la zone d'étude: les aggradationnels de court ou de long termes, les filtres primaires et les chenaux à exutoire libre ou bouché.La comparaison de ces types de chenaux avec la classification antérieure de Wilson (1973) montre un certain degré de correspondance. Un certain nombre de changements dans la distribution spatiale de types similaires de chenaux ont cependant eu lieu depuis cette étude précédente, principalement dans la partie supérieure de la zone d'étude. Les raisons des changements et ceux qui pourraient survenir sous peu ont été prévues sur base des découvertes de la présente étude.
Environmental determinants of fecundity in klipspringer (Oreotragus oreotragus)
Authors: DUNBAR R. I. M. 
Published: April 2008

Summary

Data from seven populations of klipspringer, a small African antelope, are analysed to determine the extent to which altitude, temperature, rainfall and graze quality influence fecundity.
Temperature is the only variable that has a significant effect.
It is suggested that, even in the tropics, the energetic cost of maintaining thermoregulation at moderate to high altitudes can be significant and that this leaves the female with less energy to spare for investing in offspring.

Résumé

On analyse les données portant sur sept populations d'oréotragues, petites antilopes africaines, pour déterminer dans quelle mesure l'altitude, la température, les chutes de pluie et la qualité de la nourriture influencent la fécondité.
La température est la seule variable qui ait un effet significatif.
On suggère que, même sous les tropiques, le coût énergétique de la thermorégulation en moyenne et haute altitude peut être significatif et qu'il laisse à la femelle moins d'énergie à investir dans une descendance.
Spatial distribution and nutritive value of two species of Cochlospermum for warthog (Phacochoerus aethiopicus Pallas) in Kainji Lake Park, Nigeria
Authors: AMUBODE F. O. 
Published: April 2008

SummaryPercentage composition of woody plants in five vegetation types and activity sites of warthog were used to evaluate the spatial distribution of Cochlospermum spp. in Kainji Lake National Park. Cochlospermum planchoni and Cochlospermum tinctorium were mostly encountered in Acacia forest. These species constituted between 7% and 18% of the plant species in the activity sites of warthog. The activity site with the highest composition of Cochlospermum spp. contained the lowest density (1–2 km‐1) of warthog. Although C. planchoni contained more nutrients than C. tinctorium, each of these species may be useful for the total ash (93‐0g kg‐1) and crude fibre (423‐0g kg‐1) quantities that are being utilized as nutrients by warthog. Consequently, Cochlospermum spp. could be established in conservation areas either to eradicate the use of artificial salt licks or to reduce the percentage of bare ground prone to trampling and erosion.
Climatic influences on the behavioural ecology of Chanter's mountain reedbuck in Kenya
Authors: ROBERTS S. C. , DUNBAR R. I. M. 
Published: April 2008

SummaryThe effects of rainfall and temperature on the behavioural ecology of Chanler's mountain reedbuck (Redunca fulvorufula fulvorufula Rothschild) were examined on ranchland near Gilgil, Kenya. Ambient temperature was shown to be the proximate determinant of diurnal activity and rumination patterns. Mountain reedbuck were active during early morning and late afternoon, but rested and abandoned rumination when temperatures peaked at midday. There was close synchrony in levels of activity, rumination and use of cover and shade between males and females. Seasonal variations in time budgets were strongly influenced by rainfall patterns. Analyses revealed a one‐month lag between rainfall and both peak grass growth and a decrease in rumination frequency. The proportion of time allocated to feeding decreased one month later, and was coincident with an increase in the proportion of grass in the diet. Reedbuck may therefore be prevented from exploiting high‐quality new grass, possibly by gut‐fill or induced imbalances in rumen pH. It is suggested that the unexpectedly high levels of browse in the diet is an adaptive response to low rainfall during the preceding two months.
Emergence, basking behaviour, mean selected temperature and critical thermal minimum in high and low altitude subspecies of the tropical lizard Mabuya striata
Authors: PATTERSON J. W. 
Published: April 2008

SummaryEmergence, basking behaviour, selected temperature, and critical thermal minimum were studied in warm and cold acclimated groups of two subspecies of the lizard Mabuya striata. The high‐altitude M. s. punctatissima emerges earlier than the low‐altitude M. s. striata. Under conditions of warm acclimation, M. s. punctatissima has a longer initial bask. The two subspecies do not differ in either mean selected temperature or critical thermal minimum, although in both cases values for cold acclimated lizards are lower than for warm acclimated lizards. I have previously demonstrated differences between the subspecies in the pattern of thermal acclimation of rate of oxygen consumption. I thus consider that M. striata is static in some aspects of its thermal biology but labile in others.
Geography and phytosociology of Acacia tortilis in the Sudan
Authors: KENNENNI LEGESSE 
Published: April 2008

SummaryA description is given of the geographical, phytosociological and environmental position of Acacia tortilis. This species has a distinctive geographical range restricted mainly to the arid and semi‐arid regions of northern, eastern and southern Africa and the Arabian peninsula. In the Sudan it is a characteristic species along seasonal water courses (wadis) and in areas receiving run‐off. Its distribution is mainly determined by rainfall, soil and topography.There are three subspecies of A. tortilis widely distributed in the Sudan: A. tortilis subsp. tortilis (Forsk.) Hayne, A. tortilis subsp. raddiuna (Savi) Brenan and A. tortilis subsp. spirocarpa (Hochst. ex A. Rich.) Brenan.The vegetation in the study area is described by phytosociological releves; different plant community types are identified and some important climatic, edaphic and biotic factors are related to the community types. Special attention is paid to different phytosociological aspects of A. tortilis, such as cover, frequency and stratification.RésuméOn donne une description de la position de l′Acacia tortilis, aux points de vue géographique, phytosociologique et environnemental. Cette espèce a une distribution géographique distinctive, limitée principalement aux régions arides et semiarides du nord, de I'est et du sud de 1'Afrique et de la Péninsule Arabique. Au Soudan, c'est une espèce caractéristique des bords des cours d'eau saisonniers (oueds) et des régions temporairement inondèes. Sa distribution est principalement déterminée par les chutes de pluie, le sol, et la topographic Il y a trois sous‐espèces d'A. tortilis qui sont largement répandues au Soudan: A. tortilis tortilis (Forsk.) Hayne, A. tortilis raddiana (Savi) Brenan et A. tortilis spirocarpa (Hochst. ex A. Rich.) Brenan.La végétation de la zone de recherches est décrite au moyen de relevés phytosociologiques; l'on identifie différents types de communautés végétales et l'on y associe certains importants facteurs climatiques, édaphiques et biotiques. On accorde une attention spéciale aux différents aspects phytosociologiques d'A. tortilis, comme la couverture, la fréquence et la stratification.
A reappraisal of the reproductive ecology of Arvicanthis in Africa
Authors: FISHER MARTIN 
Published: April 2008

Summary Arvicanthis (Rodentia, Muridae) is widespread in tropical Africa, and its ecology has been studied in both East and West Africa under various climatic regimes. In order to take an overall look at the reproductive ecology of Arvicanthis in Africa, data were extracted from the literature on the climate and reproductive ecology and weight of Arvicanthis at eight localities. Relationships between aspects of reproductive ecology and climate were explored statistically.The length of the breeding season of Arvicanthis shows a strong, non‐linear relationship with the number of ‘humid’ months in a year (as determined from a standard climograrn), but weight of adult males and females, number of implanted embryos and proportion of reproductively active females do not appear to be correlated with climate. The available evidence does not support the hypothesis that populations of Arvicanthis in hotter‐drier environments are more r‐selected, and that populations in cooler‐wetter localities are more K‐selected. The necessity for consistent interpretations of r‐K theory and standardization of measures of ‘stress’ and ‘predictability’ is discussed.Résumé Arvicanthis (Rodentés, Muridae) est répandu en Afrique tropicale et on a étudié son écologie en Afrique de 1'Est et de 1'Ouest sous différents régimes climatiques. Pour obtenir une vue générale de l'écologie de la reproduction d'Avicanthis, en Afrique, nous avons repris des données dans la littérature sur le climat, la reproduction et le poids, en huit endroits. On a étudié les relations statistiques entre la reproduction et le climat.La durée de la saison de reproduction d'Arvicanthis montre une relation étroite non linéaire avec le nombre des mois humides par an, (On l'a déterminé avec un clirnogramme standard), rnais le poids des adultes mâles et femelles, le nombre d'embryons implantés et la proportion de femelles qui participent à la reproduction ne semblent pas liés au climat. Les chiffres ne confirment pas l'hypothèse colon laquelle les populations d'Arvicanthis sont plus r‐sélectionnées, ni que les populations d'emplacements plus froids et plus humides sont plus K‐sélectionnées. On discute la nécessité d'interprétations fiables de la théorie r‐K et de la standardisation de mesures de ‘stress’ et de ‘probabilité’.
Causes of mortality of nyala (Tvagelaphus angasi Gray) in Lengwe National Park, Malawi
Authors: MKANDA F. X. , MUNTHALI S. M. 
Published: April 2008

SummaryThe nutritional and reproductive status of the nyala were assessed during each annual culling operation from 1981 to 1988. The nutritional condition was assessed by using kidney fat index (KFI) values whilst the reproductive status was determined by calculating proportions of pregnant and lactating females. There was a higher percentage of both males and females in poor condition than those either in medium or good condition. This occurred regardless of the amount of early dry season rainfall. There was an increase in the proportion of pregnant or lactating sub‐adult and old females whilst the proportion of breeding adults declined. Overall, however, significantly (P< 0.05) more adults were conceived. These results help to support the view that nyala mortality may not have been caused by starvation alone.RésuméOn a évalué le statut alimentaire et reproductif du nyala au cours de chaque opération annuelle de prélèvement, entre 1981 et 1988. On évaluait le statut alimentaire en utilisant les valeurs d'index de graisse rénale (KFI) tandis que le statut de reproduction était déterminé en calculant les proportions de femelles prégnantes et allaitantes. Il y avait un pourcentage supérieur de mâles et de femelles en mauvaise condition qu'en moyenne ou en bonne condition. Ceci s'observait indépendam‐ment de l'importance des chutes de pluie du début de saison sèche. Il y avait une augmentation de la proportion de femelles subadultes et âgées qui étaient pregnantes ou allaitantes alors que baissait la proportion des adultes participant à la reproduction. Pourtant, globalement, un nombre significativement (P < 0,05) plus étlevé d'adultes se reproduisaient. Ces résultats renforcent l'idée que la mortalité des nyalas ne peut pas avoir été causée uniquement par la faim.
Horn and body measurements of topi in relation to a variable mating system
Authors: FORD ANDREW BALM , BLAKEMAN SARAH 
Published: April 2008

SummaryWe immobilized 32 adult male topi and six adult females from a population in the Parc National de l'Akagera, Rwanda. Adult males were heavier and longer than adult females, and had greater body and neck girths, thicker horns and greater horn spans. Horn span was negatively related to horn length in adult males. Most males darted held resource‐based territories, and territorial males were longer than non‐territorial males. Finally, resource‐defending males measured during the present study were lighter than lek territory holders measured in the same area 17 years before, indicating that the shift in mating system from lek‐breeding to resource defence has been accompanied by a corresponding change in the mean weight of territorial males.RésuméNous avons immobilisé 32 máles adultes et six femelles adultes d'une population de topis au Parc National de l'Akagera, Rwanda. Les adultes máles sont apparus plus lourds et plus longs que les femelles, ont un corps et un tour de cou plus grands, et des cornes plus épaisses et plus écartées. Chez les máles adultes, l'écartement des cornes s'est avéré inversément proportionnel à leur longueur. La plupart des máles immobilisés étaient détenteurs de territoires basés sur des ressources, et les máles territoriaux sont apparus plus longs que les non‐territoriaux. En somme, les máles défendant un territoire basé sur des ressources sont apparus plus légers que les détenteurs d'arènes, examinés au même endroit 17 ans plus tot, ce qui montre que le passage d'un système d'accouplement basé sur la reproduction en arène à celui basé sur la défense de ressources s'est accompagné par un changement corres‐pondant du poids moyen des máles territoriaux.
Condition, growth and reproduction in female red lechwe (Kobus leche leche Gray 1850)
Authors: WILLIAMSON D. T. 
Published: April 2008

SummaryInformation on condition, growth and reproduction was collected from a sample of 155 female lechwe in the Linyanti Swamp, northern Botswana. Condition varied significantly with age, reproductive state and season and indications were found of relationships between body mass and the attainment of puberty in young females and body mass and the fertility of adult females. There were also indications that the population was under nutritional stress because of high water levels and that this had caused reductions in the growth rate and fertility of young females.It is suggested that the sensitivity of young females to adverse environmental conditions could be exploited to optimize population monitoring for conservation purposes by using them as an indicator class, rather than monitoring the entire population. Because of relationships between condition, growth and reproduction, it is also suggested that long‐term monitoring of condition should form part of any effort to understand population dynamics.
Development of the foetal membranes in the cane rat (Thryonomys swinderianus): a re‐interpretation
Authors: ODUOR‐OKELO DOMINIC , GOMBE SAMSON 
Published: April 2008

SummaryThe morphogenesis of the foetal membranes of the African cane rat (Thryonomys swinderianus, Temminck) was studied and compared with that of the caviomorphs from South America. Like the guinea pig and chinchilla, implantation in the cane rat is interstitial, amniogenesis is by cavitation, there is very early and complete inversion of yolk sac endoderm, there is a well‐developed subplacenta which persists throughout gestation, and the interhaemal membrane is haemomonochorial in nature. The phylogenetic significance of these findings are discussed in the light of long geographical and temporal separation between the continents.
A new approach for detecting visibility bias for the fixed‐width transect method
Authors: SINNARYS A. S. M. , HEBRARD J. J. 
Published: April 2008

SummaryFour road counts and four series of daily road counts of 28.4% sampling intensity were carried out at Wildlife Ranching and Research Ltd (WRR), Athi River, Kenya, between December 1966 and July 1987 to test the applicability of the method to the WRR environment. The results, however, exhibited high variation. Difficulties were encountered when applying the Anderson & Pospahala (1970) method to detect the existence of visibility bias in the distribution of Thomson's gazelle. An alternative approach, based on the regression of group size on the right angle sighting distance was applied to detect the existence of visibility bias.