African Journal of Ecology

Published by Wiley
Online ISSN: 1365-2028
Publications
Article
In August 2004, hippo mortality in the waters of Kazinga Channel, Lakes George and Edward within Queen Elizabeth National Park (QENP) was observed. Veterinary investigation confirmed the disease killing hippos to be anthrax, using clinical, postmortem and laboratory diagnosis, including the polymerase chain reaction technique. Anthrax is believed to have occurred in QENP in 1959, 1962 and 1991 amongst Hippopotamus amphibious but these was not as devastating as the outbreak of 2004-2005. During the outbreak, 306 hippopotami representing 11.63%, 63 zebras representing 1.47%, 60 buffaloes representing 0.9%, thirteen warthogs representing 0.69%, twelve kobs representing 0.07%, three waterbucks representing 0.09% and five elephants representing 0.02% died. A multisectoral National Taskforce was set up, to among other things contain the disease at source and halt its spread. Carcass disposal by burying and burning, decontamination of disposal sites by 10% formaldehyde, ring vaccination of cattle and sheep using blanthrax vaccine and community sensitization, were carried out by the taskforce. A surveillance programme is in place.
 
Article
A multi-proxy analysis of microfossils from sedimentary records, together with evidence from historical and archaeological data, has provided evidence of vegetation dynamics and human environment interactions in western Uganda for the last 1000 years. Pollen, fungal spores and phytoliths extracted from sediment cores obtained from a papyrus swamp at Munsa archaeological site indicate a relatively wet and forested environment in western Uganda prior to ca 1000 yr bp (cal 977–1159 ad). A subsequent decline in forest vegetation occurred from ca 920 yr bp (cal 1027–1207 ad). However, the deforestation period occurred during a wet period as registered in the River Nile water records, suggesting a human induced deforestation at Munsa rather than reduced precipitation. Increased numbers of herbivores, presumably domesticated cattle, postdeforestation are evidenced by the presence of dung fungal spores and broad accord with the archaeological evidence for initial occupation of the site at Munsa and the establishment of a mixed economy based on crops, cattle and iron working between 1000 and 1200 ad. From ca 200 yr bp (cal 1647–1952 ad), forest recovery occurred at Munsa site and appears to reflect abandonment of the site, as suggested by archaeological evidence, possibly following a period of prolonged drought and famine between 1600 and 1800 ad, as recounted in the oral rich traditions of western Uganda and also reflected by low water levels of River Nile.
 
Monthly percentage of Pterocles decoratus and P. exustus shot in breeding condition, by region; , males; , females, labels indicate year of collection
Percentage of female sandgrouse and of guineafowl/spurfowl shot in breeding condition, and proportions of months with over 25% breeding individuals in relation to shooting seasons, by region; , % individuals; , % months; horizontal lines indicate shooting season. Sample sizes are shown above bars.
Binomial model testing the effects of year and sex (data for August and September only) on the proportion of birds shot in breeding condition, for two species of sandgrouse and Francolinus leucoscepus. N=total number of birds shot in breeding condition, **P<0·01, *P<0·05, NS P<0·05
Article
Variation in gonadal size of shot black-faced sandgrouse, Pterocles decoratus, and chestnut-bellied sandgrouse, P. exustus, considered to be indicative of their breeding condition, was studied to examine whether or not breeding seasons fall within the set shooting seasons for different parts of Kenya, and to reveal a possible relationship between rainfall patterns and the onset of breeding. Analysis of an eleven-year data set shows large overlap between the present shooting season for sandgrouse and their main breeding period in southern Kenya, while seasons for other areas and other gamebird species seem appropriate in most years. Cumulative rainfall from four to six months earlier correlates positively with the proportion of birds breeding, while rainfall in the period shortly before breeding does not. These findings support the hypothesis that sandgrouse breed when seeds are likely to be most abundant. Results from this study further suggest that incubating females frequent waterholes more often than do males, possibly due to a higher water deficit. This hypothesis, however, needs further field testing with a genuinely random sample.
 
Article
The paper is concerned with the changing relation between elephant populations and vegetation in north Bunyoro, Uganda. The history of the area over the past 100 years is briefly described, particularly in terms of changing human populations and contraction of the elephant range. The main features of the environment, including vegetation types and distribution, annual burning, other species of large mammals (including the results of aerial counts) and birds are described. The main results of investigations on the elephant populations in the area, dealing with numbers, distribution and movements, population density distributions, and social organisation iocluding group size frequencies and structure, are presented. From a population of about 10,000 elephants over 1,000 have been cropped or shot on control in the area since 1965. The results of detailed analyses of material derived from these operations are presented and discussed. Material from the cropping operations represents a cross-section of the population and all animals sampled have been aged from the dentition. It is concluded that the mean daily food intake (wet weight) is 4% of live weight for all classes except lactating females; results of studies of food quality are discussed and a possible explanation for the de-barking of trees presented. The physical condition of elephants in several populations has been compared and appears to be poorer when less browse is available. Growth equations are presented for height and weight; the male shows a post-pubertal growth spurt. Various reproductive parameters are examined including age at puberty, pregnancy rate, and the seasonal cycle. Seasonal conceptions are delayed in North Bunyoro in relation to their timing north of the River Nile and it is suggested that the delay is nutritionally-induced. Recruitment has been falling in this population and this decline is likely to continue in the absence of effective management. Some undesirable consequences of extensive control-shooting are mentioned. The analysis of the elephant populations indicates that they are at densities in excess of the carrying capacities of the habitats, and the continuing changes in these habitats are described. In the grassland and wooded grassland areas the destruction of woodland has progressed radially, a zone of damage about 15–20 km wide having moved outwards through the range. This is consistent with destruction mainly by elephants rather than by fire. The influence of elephants on the forest edge and on the areas of regeneration inside the forest, created by management, is described. Finally specific proposals that have been presented to the National Parks and Forest Department are discussed. These involve rational cropping of over 4,000 elephants over the range and the construction of elephant-proof barriers, the control of fire, and the declaration of a Conservation Area with a statutory Authority on which the various interests concerned would be represented.
 
Article
The size of the Tilapia nilotica population in Lake George was determined using purse seines. Production, mortality rate, size at maturity, and other parameters of the population were also determined. In Lake George, the factors that regulate the population of T. nilotica are both natural and artificial. The restricted size of nursery zones, strong fish-killing storms, predation and old age are some of the natural regulators. For the adult population, mortality due to these factors is low (natural mortality coefficient, M=0.1). However, commercial fishing appears to have a stronger controlling force. Since the intensification of commercial fishing in 1950, the size of the fish caught has been decreasing, whereas the number of fish caught has been increasing yearly, probably as a result of increasing effort and the use of small mesh nets. These two trends may be the cause for T. nilotica to mature at a smaller size than they did 15 years ago.
 
Article
Lemniscomys striatus was radio-tracked in the Imperata-Cymbopogon grassland of the Queen Elizabeth National Park in Uganda. Home range sizes calculated by Ranges V® using the minimum convex Polygon method (at 95%) in the postburnt grassland were on average 4.8 times larger than those before the fire. An inverse relation between home range size and population density was found. Lemniscomys striatus was diurnal with two activity peaks during daylight, but activity ended only after dusk. On a étudiéLemniscomys striatus par radio-tracking dans la prairie àImperata-Cymbopogon du Parc National Queen Elizabeth, en Ouganda. La taille des territoires calculées par Ranges V® en utilisant la méthode du polygone convexe minimum (à 95%) dans la prairie après les feux, était en moyenne 4,8 fois plus grande que celles d' avant les feux. On a découvert une relation inverse entre la taille du territoire et la densité de population. Lemniscomys striatus est diurne, avec deux pics d'activité pendant la journée, mais son activité ne cesse qu' après le crépuscule.
 
Article
Data were collected in Kenya on the movements of individually recognizable wild eland over a 30-month period. Further information on movement was obtained from monthly ground counts of Nairobi National Park, and two aerial censuses of the Park and Athi Kapiti plains. Results indicated that adult male eland had restricted home ranges, but that females and juveniles carried out extensive seasonal movements between open grassland and bushed habitats. The numbers of eland in the Park were found to be related to rainfall over the previous two months in the areas outside the Park. It was concluded that females and juveniles were taking advantage of seasonal food abundance in open grassland areas, where the formation of large groups gives protection to small-sized juveniles.
 
Article
While several authors suggest that bushbuck (Tragelaphus scriptus Pallas) from tropical areas with an approximately bimodal rainfall pattern breed throughout the year, there is also a report of seasonal breeding in this species. In this study, we provide indirect evidence of seasonality in reproduction by analysing behavioural data (e.g. rates of mixed-sex sightings) in a population of bushbuck inhabiting an equatorial savannah ecosystem in western Uganda. Observation rates of mixed-sex sightings were correlated with rainfall patterns. We suggest that peaks in reproductive behaviour following the wet season may be advantageous if calves are born during the next wet season, when fresh vegetation is available. Alors que plusieurs auteurs suggèrent que le bushbuck (Tragelaphus scriptus Pallas) des régions tropicales qui ont un régime de pluies à peu près bimodal se reproduisent tout au long de l’année, il y a aussi un rapport signalant une reproduction saisonnière chez cette espèce. Dans la présente étude, nous apportons des preuves indirectes d’une saisonnalité de la reproduction par l’analyse des données comportementales (e.g. taux d’observations de sexes mélangés) dans une population de bushbucks habitant dans un écosystème de savane équatoriale, dans l’ouest de l’Ouganda. Les taux d’observations de groupes mélangés étaient liés aux chutes de pluies. Nous suggérons que les pics observés dans le comportement reproducteur en fonction de la saison des pluies peuvent être bénéfiques si les jeunes naissent durant la saison des pluies suivante, lorsque la végétation fraîche est abondante.
 
Article
It has been suggested that all species of spiral-horned antelopes (Tragelaphini) lack territoriality. Furthermore, some authors suggested that bushbuck (Tragelpahus scriptus) males form dominance hierarchies. In this study, we investigated the dominance relationships in two groups of free-ranging bushbuck males in Queen Elizabeth National Park, Uganda. Adult males dominated young-adult bachelors and subadult males, but no distinct dominance relationships were found among adult males. Landau′s index of linearity revealed no linear dominance hierarchy in the study populations. Our results support the idea that adult males are territorial, and overt aggression is directed almost exclusively towards bachelors that challenge territory holders. On a suggéré que toutes les espèces d’antilopes à cornes spiralées (Tragelaphineae) ne montraient pas de territorialité. Qui plus est, certains auteurs ont suggéré que les mâles Guib harnaché (Tragelaphus scriptus) formaient des hiérarchies par dominance. Dans cette étude, nous avons cherché les relations de dominance dans deux groupes de mâles Guib harnaché vivant en liberté dans le Parc National Queen Elizabeth, en Ouganda. Les mâles adultes dominaient les jeunes mâles célibataires et les mâles sub-adultes, mais on n’a trouvé aucune relation de dominance distincte entre les mâles adultes. L’index de linéarité de Landau n’a révélé aucune hiérarchie linéaire de dominance dans les populations de l’étude. Nos résultats soutiennent l’idée que les mâles adultes sont territoriaux, et toute agression manifeste est dirigée presque exclusivement vers les jeunes célibataires qui défient ceux qui détiennent un territoire.
 
Article
The foraging behaviour and food selection of bushbuck (Tragelaphus scriptus) were studied in the Queen Elizabeth National Park, western Uganda. Forty-three plant species were consumed by bushbuck, consisting of two tree, eight shrub, eighteen perennial woody herb, thirteen annual non-woody herb and two climbing herb species. No significant seasonal variation in time allocated to feeding and performing miscellaneous activities per unit distance covered whilst foraging was recorded. This suggests that major plant species for foraging were available to the animals in sufficient quantities in both seasons. However, there were seasonal changes in the proportions of different plant species in the diet, although none of these dissimilarities was significant. Males spent insignificantly more time feeding than females. Bite size, established for major food plant species, was inversely related to bite rate and discussed in terms of plant-part selection. The study also compared foraging behaviour of bushbuck observed between 1974 and 1976 (Okiria, 1980, African Journal of Ecology, 18, 11-17) with that today and discusses it in the light of changes in vegetation observed over the last 35 years in the study area.
 
Article
SummaryA study to investigate some aspects of the social biology of bushbuck (Tragelaphus scriptus Pallas 1776) was carried out in a 2.59 km2 study area in the Nairobi National Park, Kenya.Observations throughout 1966 using binoculars and photography identified thirty-one male and thirty-three female bushbuck. Together with an estimated fourteen juveniles, the density in the study area was 30.1/km2.Distribution is aggregated with loose family groups concentrating around forest edge areas near to dams or river pools. Home ranges varied from 20 ha for sub-adult males to 5 ha for adult males and 2.5 ha for females.Bushbuck are predominantly solitary with 53.7% of all sightings being of lone animals; 14% of associations were of an adult female with a single calf and the commonest adult association (8%) was a single male with a single female. There is a strong mother-young relationship. Very young calves lie in concealment away from the mother during the early days of their lives.Agonistic encounters between males vary in intensity from play fighting in sub-adults to lateral intimidation display and overt conflict. The presence of a female, assumed to be in oestrous, sometimes stimulates males to intense aggression and at such times, a single male forms and defends a mating association with the female. Territorial defence was not observed.Bushbuck often associate with other species, particularly impala and baboons. They show a negative reaction to tick-birds which may be one reason for their often having heavy infestations of ticks and flies.Predator avoidance relies largely on crypsis and ‘freezing’ followed by rapid flight through dense vegetation.RésuméUne étude pour approfondir quelques aspects de la biologie sociale du Guib harnaché (Tragelaphus scriptus Pallas 1776) fut entreprise sur une surface de recherche de 2.59 km2 au Parc National de Nairobi, Kenya.Tout au long de 1966, des observations faites aux jumelles et par photographies, ont permis d'identifier 31 mâles et 33 femelles de Guib. Avec une estimation de 14 juvéniles, la densité dans la zone d'étude est de 30.1/km2.
 
Article
Spatial and temporal habitat use of kob antelopes (Kobus kob kob) have been investigated in the Comoé National Park (Ivory Coast, West Africa) by use of radio telemetry. A total of 23 kob were equipped with radio collars and radio tracked for up to 15 months. Home ranges of males were smaller and those of females larger than expected from theoretical models. Adult males used smaller areas than adult females and did not show seasonal home range shifts. Daily distances travelled did not differ between sexes. Kob walked less during the night than by clay and covered shorter distances in the wet season. Whereas an increase in home range overlap between females resulted in higher rates of association among individuals, association of adults of mixed sexes was not correlated with the degree of home range overlap. Territorial behaviour of males and predator avoidance by females are suggested to explain the sex-specific differences in home range size of adults and the deviation from the predicted sizes. Predator avoidance is presumed as the main reason for the reduced walking distances at night as well as in the wet season. Reproductive behaviour and feeding ecology are assumed to determine the degree of association of conspecifics.
 
Article
(1) Food selection of aardwolves was studied by a comparison of faecal contents with available termite populations. Observations are reported on the foraging behaviour, and on aspects of termite biology which expose various species to predation. (2) The aardwolf diet shows a very high selectivity for one species of termite, Trinervitermes bettonianus in the Serengeti and ecologically similar species elsewhere. (3) Both morphology and foraging behaviour are very well adapted to feeding on Trinervitermes bettonianus or similarly behaving termites. The aardwolf does not dig for food; hearing is probably an important sense used for locating prey. (4) Various aspects of the termites' protection against aardwolf predation are discussed. (5) The aardwolf diet shows an increase in variety during the rains; the cause of this is discussed. (6) Some brief notes are made about territorial behaviour, scent marking and the use of middens. (7) As a management recommendation regular grassland burning is suggested for areas where the presence of aardwolves is considered desirable.
 
Article
The oribi (Ourebia ourebi, Zimmermann, 1783) is a small species of antelope widely represented across open grasslands of sub-Saharan Africa. Although largely territorial, differences in group size and mating systems (monogamy/polygamy), have been linked to habitat conditions and population density. At high population densities, additional males are recruited to assist in territorial defence. Other factors which might impact on group size, include predation threat, especially at low population densities. In this study (1995–98), we recorded group sizes of oribi across two contrasting areas (c. 300 km2 each) of Zambia with (Kafue), and without (Bangweulu), large vertebrate predators. A total of 412 groups was recorded across the two sites, with mean sizes of 2.31 (n = 217) at Bangweulu and 2.33 (n = 195) at Kafue. The modal group size was two throughout (range 1–6). Groups were more variable in size and sex composition at Kafue than at Bangweulu, but there was no significant difference in estimates of population density between sites. Mean estimates were 2.02 and 1.90 km−2 for Bangweulu and Kafue, respectively. Sex ratios (males : females) were biased towards females (1 : 1.72 and 1 : 3.55, respectively) at both sites. Adult males were particularly scarce at Kafue. However, values of density and group size, were both unexceptional for the species. Whilst a modal group size of two is consistent with a monogamous mating system, variations in group composition and size were more difficult to explain. Adult females appeared to retain or recruit additional animals to groups, irrespective of the needs of territorial defence. This suggests that vigilance is an important function of groups on large open plains, especially in the presence of predators. By extension, reversed sexual dimorphism in oribi could reflect increased selection for vigilance duties in females. Predators had no apparent effect on population density, but oribi groups were more variable in size and sex composition in their presence. Adult males may be particularly vulnerable to predation when defending territorial borders at low population densities. However, further work is needed to define group dynamics in this species and to identify causes of mortality amongst adult males. L'oribi (Ourebia ourebi, Zimmermann, 1783) est une petite espèce d'antilope largement présente dans les prairies ouvertes d'Afrique sub-saharienne. Bien qu'elle soit principalement territoriale, on a pu lier des différences dans la taille des groupes et dans le système d'accouplement (monogamie/polygamie), aux conditions de l'habitat et à la densité de la population. Lorsque la densité de population est élevée, des mâles supplémentaires sont recrutés pour aider à la défense territoriale. D'autres facteurs qui pourraient influencer la taille des groupes incluent la menace des prédateurs, spécialement si la densité de population est faible. Dans cette étude (de 1995 à 1998), nous avons relevé le taille des groupes d'oribis dans deux zones très différentes (env. 300 km2 chacune) de Zambie avec (Kafue) et sans (Bangweulu) grands vertébrés prédateurs. On a relevé un total de 412 groupes pour les deux sites, dont la taille moyenne était de 2.31 (n = 217) à Bangweulu et de 2.33 (n = 195) à Kafue. La taille modale du groupe était deux partout (allant de 1 à 6). Les groupes étaient plus variables en ce qui concerne la taille et le sex-ratio à Kafue qu'à Bangweulu, mais il n'y avait pas de différence significative des estimations de densité de population entre les sites. Les estimations moyennes étaient respectivement de 2.02 et de 1.90/km2 pour Bangweulu et pour Kafue. Le sex-ratio (mâles : femelles) était biaisé en faveur des femelles (1 : 1.72 et 1 : 3.55 respectivement) sur les deux sites. Les mâles adultes étaient particulièrement rares à Kafue. Cependant, les valeurs, tant pour la densité que pour la taille des groupes, n'étaient pas exceptionnelles pour l'espèce. Si une taille modale de groupe de deux correspond bien à un système de reproduction monogame, les variations de la composition de la taille des groupes sont plus difficiles à expliquer. Il semble que les femelles adultes maintiennent ou recrutent des animaux supplémentaires pour le groupe, quels que soient les besoins de défendre le territoire. Ceci laisse penser que la vigilance est un fonction importante pour les groupes qui vivent dans de vastes plaines ouvertes, spécialement lorsqu'il y a des prédateurs. Par extension, le dimorphisme sexuel inversé chez les oribis pourrait refléter une sélection accrue pour les devoirs de vigilance chez les femelles. Les prédateurs n'ont pas d'effets visibles sur la densité de la population, mais les groupes d'oribis ont une taille et un sex-ratio plus variables en leur présence. Les mâles adultes pourraient être particulièrement vulnérables à la prédation lorsqu'ils défendent les limites du territoire et que la densité de population est faible. Cependant, d'autres travaux sont nécessaires pour définir la dynamique du groupe de cette espèce et pour identifier les causes de mortalité des mâles adultes.
 
Article
We tested the hypothesis that elephant distribution inside the Nazinga Game Ranch (Southern Burkina Faso) during the wet season is influenced by villages outside, while in the dry season elephants are restricted only by water. Occupancy was evaluated by recording elephant dung-piles on 54 line transects in each of three seasons: wet 2006, dry 2007 and dry 2008. We measured the distance of each transect from nearest villages, nearest permanent water sources, nearest guard posts and tourist camps. The results were unexpected: elephant occupancy in the wet season was independent of villages but influenced by poaching, while their occupancy in both dry seasons was determined by the proximity of villages as well as water. In the dry season, elephants were attracted to villages by grain stores and fruiting trees. There has been a dramatic shift in the dry season distribution of elephants, and consequently in browsing pressure, over the last two decades. We suggest that this change is a consequence of the expansion of human activities outside the ranch. This study shows that the effects of growing human disturbance on elephant populations in small protected areas are not predictable. Correcting for spatial autocorrelation had a negligible effect upon the models.
 
Article
The study was done in Lake Mburo area, Uganda, consisting of Lake Mburo National Park and surrounding ranches. The study involved monitoring changes of output of helminth eggs per gram (e.p.g.) by impala for 12 months. Fresh faecal samples, 178 in total, were collected from the rangeland and subjected to floatation and culture tests. There was a peak faecal e.p.g. output from March to April and from October to November. This period coincided with time of high rainfall and calving peak of impala. There was no faecal e.p.g. observed during the dry spell from June to July. Cette étude fut menée dans la région du Lac Mburo en Uganda, comprenant le Lake Mburo National Park et les ranchs avoisinants. Elle a impliqué la surveillance continue des variations de l’expulsion d’oeufs d’helminthes par gramme (e.p.g.) par les impalas durant 12 mois. Au total, 178 échantillons fécaux frais furent collectés dans la zone d’étude et soumis à des tests de flottation et de culture. On a constaté un pic d’expulsion d’e.p.g. fécaux de mars à avril et d’octobre à novembre. Cette période coïncidait à l’époque des fortes pluies et du pic des mises bas de l’impala. On n’a observé aucune e.p.g. fécale durant la période sèche de juin à juillet.
 
Article
Hipposideros commersoni is a large microchiropteran bat endemic to Madagascar. We analysed fragments of its prey from faeces and from underneath feeding perches to describe its diet from four sites. Diet was similar across sites and Coleoptera was the main prey item by percentage volume (75%), followed by Hemiptera (13%). Carabidae and Scarabidae were the most frequent coleopterans found in the diet. Direct observations (n = 3) were made of bats flying short distances from perches along forest trails to prey on Cicadidae (c. 20 mm in length) located on tree trunks. There were differences in the composition of faecal samples collected form netted bats and pellets collected under feeding perches, with the latter consisting of more Blattoptera (Blattellidae 'cockroaches'). Hipposideros commersoni appears to have a unique foraging behaviour and diet among Malagasy microchiropterans and its preference for certain Coleoptera and other large invertebrates may account for reported seasonal variation in body fattening and activity.
 
Article
Arvicanthis niloticus was radio-tracked in the grasslands of the Queen Elizabeth National Park in Uganda. Home range sizes calculated by Ranges V® using the Minimum Convex Polygon Method (at 95%) were on average 5.5 times larger in the bushland–grassland mosaic than those in the Abutilon guineense–Ocimum suave bushland. An inverse relation between home range size and population density was found. In both habitats the species was highly active during daylight hours but differed in activity patterns. L'Arvicanthis niloticus fut suivi par radio-émetteur dans la prairie du Parc National de Queen Elizabeth en Ouganda. Les tailles des domaines vitaux calculés avec Ranges V®en se servant de la méthode de polygones convexe minimum (à 95%) furent 5,5 fois plus grand en moyenne dans le terrain en mosaïque de brousse et prairie que celles dans la brousse d’Abutilon guineense–Ocimum suave. Une relation inversée entre la taille des domaines vitaux et la densité de population fut observée. Dans les deux habitats les espèces furent très actives pendant le jour mais différa dans la configuration d'activité.
 
Article
The transpiration rates of the desert isopod Hemilepistus reaumuri (Audouin and Savigny, 1826), exposed to eight different temperatures ranging from 10 to 45°C for 1 h, showed that the water loss from the body surface was higher from 35 to 45°C as compared with the lower temperatures. Higher rates of transpiration were discernible in animals previously acclimatized to 35°C or in moist conditions than in those kept at 15 or 25°C or in dry conditions. Acclimatization of the animals to 10, 25 or 35°C had a marked effect on their behaviour and activity when later exposed to rising temperatures. Exposure to 10 or 25°C for 15 days affected the feeding and assimilation rates and moisture contents, with higher temperatures increasing these rates significantly. Le taux de transpiration de l'isopode du désert Hemilepistus reaumuri (Audouin et Savigny, 1826), confrontéà huit températures différentes allant de 10°à 45°C pendant l'heure, a montré que la perte d'eau par la surface du corps était plus importante de 35°C à 45°C on comparaison avec des températures plus basses. On pouvait discerner un taux de transpiration plus éléve chez des animaux acclimatés antérieurement à 35°C ou à des conditions humides que chez ceux qui avaient été gardés à 15°C ou 25°C ou dans des conditions sèches. L'acclimatation des animaux à 10°, 25°C ou 35°C avait un effet marqué sur leur comportement et leur activité lorsqu'ils étaient ensuite exposés à des températures croissantes. L'exposition à des températures de 10° ou de 25°C pendant quinze jours affectait les taux d'alimentation et d'assimilation et le contenu en eau, les températures plus hautes faisant augmenter ces taux significativement.
 
Article
Abstract Spinal deformities in Aphanius fasciatus were observed in fish collected from polluted (S1) and non-polluted (S2) areas in the Gulf of Gabes in Tunisia. Kyphosis, scoliosis and lordosis were detected and these basic deformities frequently co-occur in varying degrees of severity. A total of 612 specimens of A. fasciatus were caught and 54 were found to be deformed, which represents 8.82%. Deformed fish were eight times more frequent in S1 than in S2, possibly indicating a relationship between pollution levels and skeletal malformation. In both sexes, variation of deformities incidence with length was very similar. The highest occurrence of deformities was observed in fish with total length Keywords: Aphanius fasciatus; Gulf of Gabes; Tunisia; pollution; spinal deformities Document Type: Research Article DOI: http://dx.doi.org/10.1111/j.1365-2028.2008.00972.x Publication date: September 1, 2009 $(document).ready(function() { var shortdescription = $(".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } $(".descriptionitem").prepend(shortdescription); $(".shortdescription a").click(function() { $(".shortdescription").hide(); $(".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher In this Subject: Zoology , Ecology By this author: Messaoudi, Imed ; Kessabi, Kaouthar ; Kacem, Adnen ; Saïd, Khaled GA_googleFillSlot("Horizontal_banner_bottom");
 
Article
The gastrointestinal parasites of the grasscutter were investigated between 1996 and 2006 using 180 grasscutters from the Accra Plains. The aim of the study was to develop strategies for the control of the parasites under captive management. The gastrointestinal tracts of the animals were examined for the presence of both helminth and protozoan parasites with the aid of a hand lens, the direct smear and Willis Flotation techniques. In all, fourteen species of helminths were found including twelve nematodes and two cestodes. Trichuris muris was the most common nematode encountered, whilst Hepatocola hepatica was the least commonly encountered nematode. Three genera of protozoans, viz, Trichomonas spp, Giardia spp and Eimeria spp were also encountered, with Giardia spp and Trichomonas spp being reported for the first time in the grasscutter. Eimeria spp were the most prevalent protozoa. The widespread occurrence of protozoal and helminthic parasites in the grasscutter suggests that routine treatment of grasscutters with coccidiostats, anti-flagellates and anthelminthics such as dimetridazole and albendazole may contribute significantly to improve productivity of animals and reduce the pressure on wild populations.
 
Article
The social organization of waterbuck in a Rhodesian game park has a profound effect on the spatial and forage-habitat utilization by different social groups. Territorial behaviour effectively prevents bachelor groups from using high quality food resources in recently burnt areas and in certain zones of the shoreline community. In order to overcome the effects of the dry season on available food resources, waterbuck practised a divergence in habitat selection from grass species in woodlands, to hydrophytic plant species along the shoreline of Lake Mcllwaine. Territory size appears to be related to the quality and availability of food resources.RÉSUMEÉL'organisation sociale du waterbuck dans une réserve de chasse de Rhodésie a un effet marqué sur l'utilisation spatiale et celle des ressources fouragéres par différents groupes sociaux. Le mode de comportement territorial prévient efficacement la formation de groupes de jeunes mǎles par l'utilisation de ressources alimentaires de haute qualité dans les zones récemment brǔlées et dans certaines zones de communautés littorales. Pour surmonter les effets de la saison sèche sur la disponibilitè de nourriture, le waterbuck pratique une diversification dans la sélection des habitats, depuis les espèces de graminées en région boisée jusqu'aux espèces de plantes hydrophytes le long des rives du lac Mcllwaine. La dimesion du territoire semble avoir rapport à la qualité et à la distribution des resources alimentaires.
 
Article
Rodent populations in cultivated and fallow fields in Tanzania were sampled by trapping. Mastomys natalensis (Smith) was by far the most abundant rodent in these habitats (62% or more of samples). Estimates of densities of this rodent were obtained by removal trapping at scattered localities in Tanzania (range 23–236 ha-1) and from a catch-mark-release (CMR) study through a seasonal cycle (range 40–384 ha-1). Home ranges were analysed using CMR data. Seasonal variation in home-range size was not found, but reproductive males “had larger ranges than females and subadults. On a prélevé au moyen de piéges des échantillons des populations de rongeurs dans des champs cultivés et dans d'autres en jachère. Mastomys natalensis (Smith) était de loin le rongeur le plus abondant dans ces habitats (62% ou plus des échantillons). On a obtenu des estimations de la densité de ce rongeur au moyen de pièges dispersés dans différentes localités en Tanzanie, les animaux n'étant pas relâches (distribution 23–236/ha), et par une étude de capture-marquage-recapture (CMR) pendant un cycle saisonnier (distribution 40–384/ha). On a analysé les espaces vitaux en se servant des données de CMR. On n'a pas trouvé de variation saisonnière de la taille de l'espace vital mais les mâles reproducteurs ont des territoires plus vastes que les femelles et les subadultes.
 
Article
This paper reports the high frequency of dental abnormality found among a population of waterbuck in Nakuru National Park, Kenya, and discusses the possible causes. The data were obtained from examination of carcasses and skeletons found in the Park–58.3% of these displayed uneven wear along the posterior tooth row, sometimes resulting in tooth loss. These patterns were found in individuals of both sexes and all ages. It is argued that this high incidence of dental abnormalities is the result of the specific conditions in which the Nakuru water-buck population live (isolation and reduced competition and predation) leading to inbreeding and increased homozygosity and a higher frequency of expressed genetic abnormalities. These conclusions may have some implications for wildlife management of isolated populations. Ce travail discute de la fréquence élevée d'anomalies dentaires constatée parmi la population de waterbucks du Parc National de Nakuru (Kenya) et examine les causes possibles de celle-ci. Les données ont été obtenues par l'examen de carcasses et squelettes trouvés dans le Parc, dont 58.3% présentaient une usure inégale le long de la rangée dentaire postérieure parfois due à la perte de dent. Cette usure est relevée chez des individus des deux sexes et de tous âges. Il est suggéré que l'incidence élevée d'anomalies dentaires est le résultat des conditions spécifiques qui régissent la population de waterbuck de Nakuru (isolation, compétition réduite et prédation) qui mènent à une consanguinité, une homozygosité accrue et une plus haute fréquence d'anomalies génétiques. Ces conclusions peuvent avoir certaines implications pour la gestion de populations sauvages isolées.
 
Article
On a découvert seize espèces de parasites lors d'une étude des métazoaires ecto-et endoparasites de Siganus sutor (Cuvier & Valenciennes, 1985), un Poisson herbivore commercialement important de la côte kéyane. Les parasites des branchies comprennent des Monogeneae (Tetrancistrum sigani Goto & Kikuchi, 1917; Microcotyle mouwoi Ishii & Sawada, 1938; Pseudohaliotrema sp.1 & sp.2, et une espèce non identifiée de Microcotylideae); des Copépodes (Caligus sp. et Hatschekia sp.) et un Icopode (une espèce de Gnathiideae). Les parasites intestinaux trouvés appartenaient aux Digeneae (Opisthogonoporoides cf. hanumanthai Madhavi, 1972; Gyliauchen papillatus Goto & Matsudaira, 1918; Hexangium sigani Goto & Ozaki, 1929; et trois autres Digenaeae non identifiés); aux Acanthocephaleae (Sclerocollum rubrimaris Schmidt & Paperna, 1978), et aux Nématodes (Procamallanus sigani Yamaguti 1935). Ces espèces sont rapportées pour la première fois sur la côte kényane. Le degré, l'intensité
 
Article
In South African West Coast, small mammals (mainly Otomys unisulcatus and Rhabdomys pumilio) constituted the bulk of the diet (90.4%), insects were a secondary food resource (4.9%). This mongoose appears to conform to the general hypothesis of a relationship between a carnivorous diet and solitary behaviour. The productivity of the 2 major prey species appears to be much higher than the food requirements of this mongoose population. This may explain the apparent lack of territoriality reported for this and other species. -from Authors
 
Article
Lechwe habitat use was studied intensively for 2.5 years and monitored for a further 7.5 years in the Linyanti Swamp, northern Botswana. It was found to be highly selective with respect to both resting and feeding sites. The selection of resting sites was probably a function of predator avoidance behaviour, while the selection of feeding sites was probably a function of pasture quality. The results of the study were consistent with the argument of IIlius & Gordon (1987) that sexual segregation of feeding sites is due to allometry of food intake and with the contention of Jarman (1974) that social factors may also affect habitat use. On a étudié intensément depuis 2.5 ans, et surveillé depuis 7.5 ans supplémentaires, la façon dont les Iechwe utilisent l'habitat dans les marais de Linyanti, au nord du Botswana. On a trouvé qu'ils étaient très selectifs, tant pour les endroits de repos que pour ceux où ils se nourrissent. La sélection des endroits de repos était liée au comportement visant àéviter les prédateurs, tandis que le choix des sites de nourrissage était probablement fonction de la qualité du fourrage. Les résultats de cette étude concordent avec la discussion de Illius & Gordon (1987) sur le fait que la ségrégation sexuelle des sites de nourrissage est due à l'allométrie de la ration alimentaire, et avec l'affirmation de Jarman (1974), que des facteurs sociaux aussi peuvent affecter l'utilisation de l'habitat.
 
Article
This study investigated the utilization of mist-belt grassland habitat by the threatened blue swallow and was conducted over three successive breeding seasons in the Blue Swallow Natural Heritage Site at Kaapsehoop, Mpumalanga, South Africa. Blue swallows significantly preferred wetlands over grasslands for foraging. Sufficient foraging habitat must be within a 1.5km radius from an active nest site. The minimum size of a pair of blue swallows home range should be 333ha, consisting at a minimum of grasslands (243ha or 73%) and wetlands (90ha or 27%). In order to conserve this threatened species, habitat transformation should not take place within a minimum radius of 1.5km of any blue swallow nest. Due to the critical dependence of the blue swallow on wetland habitat for foraging, any development outside the 1.5km radius that would affect hydrology and water quality within this range would need to be considered, and any adverse effect mitigated. Rehabilitation of areas to a grassland/wetland mosaic would rather quickly support foraging, and eventually breeding. Although a better understanding of the dynamics between wetlands and adjacent grasslands regarding blue swallow habitat requirements is needed, action can already be taken, based on our results.
 
Article
Information on condition, growth and reproduction was collected from a sample of 85 male lechwe from the Linyanti Swamp in northern Botswana. No significant seasonal variation in condition was found in lechwe males. Von Bertalanffy equations were used to document growth in body-mass, body-length, chest girth, shoulder height, neck girth and horn length. Spermatogenesis occurred by 1.5 years of age after attainment of a body-mass > 55 kg, a testis-mass > 15 g and a semeniferous tubule diameter > 120 μm. There was an hiatus of perhaps three years between the onset of spermatogenesis and successful mating. In relation to condition, growth and reproduction, a number of sexual differences were documented, which were attributed to differences in the demands of reproduction and in reproductive strategies. On a récolté des informations concernant la condition physique, la croissance et la reproduction, sur un échantillon de 85 cobes lechwe máles des Marais de Linyanti, dans le nord du Botswana. Leur condition physique ne varie pas de façon significative avec les saisons. On a utilisé les équations de Von Bertalanffy pour relier la croissance à la masse corporelle, la longueur du corps, la circonférence de la poitrine, la hauteur au garrot, le tour de cou et la longueur des cornes. La spermatogenèse se produit vers l'âge d'un an et demi, lorsque le corps a atteint un poids de plus de 55 kgs, les testicules, de plus de 15 grs, et le canal séminal, un diamètre de plus de 120 μm. Il y a un délai de près de trois ans entre le début de la spermatogenèse et le premier accouplement efficace. On présente un certain nombre de différences sexuelles en relation avec la condition physique, la croissance et la reproduction, qui sont attribuées à des différences de demandes et de stratégies de reproduction.
 
Statistics of a local puku count from the northern shore of Lake Rukwa, Tanzania
Frequency distribution of puku group size in the Lake Rukwa population (this study) compared with the group size distribution in the Kilombero Valley (Rodgers, 1984; Corti et al., 2002)
Article
The population of puku, Kobus vardonii, at Lake Rukwa, one of only two in Tanzania, is poorly known. A multi-species dry season game count carried out in Rukwa Game Reserve (RGR) in 2004 estimated a population size of 1729, but was associated with a high margin of error [coefficient of variation (CV) 0.88]. To increase the precision for the local puku population estimate, we conducted a zig-zag line transect survey restricted only to areas occupied by puku in the dry season of 2006. This survey technique produced an estimate of 776 individuals and the CV was considerably reduced to 0.29. Puku herd size was comparable with the studies carried out in the Kilombero valley, Tanzania and in Kasanka National Park, Zambia, thus broadly confirming the herding ecology of this species. We found that pukus were restricted to the central parts of the floodplains, suggesting an avoidance of habitats used by pastoralists at the edge of RGR. Compared with the estimates of the puku population made in the 1980s, the puku population has declined. We recommend regular monitoring and enforcement of the current management plan to conserve the local puku population.
 
Article
The population status and feeding habits of Hunter's antelope or hirola (Beatragus hunteri) in Tsavo East National Park were determined in this study in 1995. This is the first study that has ever been undertaken on the hirola population of about 20 animals that were translocated to Tsavo East National Park from South Garissa District in 1963. Relevant data and information were collected using different ecological research techniques. A total of eight nursery herds (5-11 individuals per herd) comprising 60 individuals, five lone bulls and 11 lone sub-adults was observed. This gave a total population estimate of 76 animals in the entire study area. Adult animals dominated the population (60.53%), indicating a population skew towards adults. The adult sex ratio was biased towards females (43.42%). Hirola were observed to feed mainly on short, green grasses. The dominant feed species were Panicum infestum, Digitaria rivae, Latipes senegalensis and Cenchrus ciliaris. Occasionally, hirola was observed to feed on forbs (e.g. Portulaca oleraceae, Tephrosia subtriglora and Commelina erecta). Results of this study show that the population growth of the hirola sub-population in the Park has been low (1.8 individuals per year). Factors thought to contribute to this low growth include predation and low genetic variability.
 
Article
After a major oil spill in a fresh water wetland, the oil was set ablaze as a clean-up measure. Nineteen years later the vegetation structure of the wetland was analysed for evidence of and information about vegetation recovery. Our results indicate that vegetation in the area (zone ‘H’) which received the direct impact of the spill is recovering but vegetation in areas downstream of the spill site (zone ‘M’) is presently being degraded due to a slow seepage of persistent crude oil from the spill site. Herbaceous production (including food crops) was negatively correlated with hydrocarbon concentrations in the soil. The present results suggest that burning as a clean-up measure is ineffective, at least in wetland ecosystems. Après une grave pollution pétrolière dans un marécage d'eau douce, le pétrole a été brûlé pour être éliminé. Dix-neuf ans plus tard, on a analysé la structure de la végétation du marécage pour servir de témoignage et d'information sur sa restauration Nos résultats montrent que la végétation de l'endroit (zone H) qui a reçu directement la pollution est en train de se rétablir mais que celle de l'endroit qui se trouve en aval (zone M) est actuellement en train de se dégrader à cause d'un suintement lent mais persistant de pétrole en provenance de l'endroit du déversement. La production herbacée (y compris les cultures) était inversément liée à la concentration des hydrocarbures dans le sol. Ces résultats suggèrent que le fait de brûler les hydrocarbures est inefficace pour nettoyer un endroit pollué, en tout cas dans les écosystèmes marécageux.
 
Article
The West African river crab, Potamonautes (Platypotamonautes) ecorssei (Marchand, 1902) is reported to occur for the first time in Ghana and for only the second time in Nigeria. Its geographical range is extended south to include the Volta river basin in Ghana, and east to northwest Nigeria, a distance of some 1200 km.
 
Article
Data on the monthly distributions of the Serengeti migratory wildebeest population between June 1960 and May 1973 have been analysed. It has been shown that the population performs an annual migration, spending the wet season on the Serengeti plains, then moving west towards Lake Victoria at the beginning of the dry season, and later north to the northern extension of the Serengeti National Park or into the Masai Mara Game Reserve in Kenya. The wildebeest return to the plains as soon as the rain begins, but if this is delayed they may move south-west from the northern areas into the corridor first. Annual differences in the pattern of the migration can be correlated with differences in rainfall. The rainfall affects particularly the timing of the movements of the wildebeest on and off the plains, and the extent to which they utilize the northern areas. A large increase in the size of the population over the years studied has resulted in a greater utilization of the northern areas. It has been shown that about half the total range of the wildebeest population is outside the boundaries of the Serengeti National Park, and it is therefore important that these areas should be protected if such a large population is to survive.
 
Article
The scarcity of dugong (Dugong dugon Miiller) throughout their former range and lack of knowledge of the species' ecology justifies this record of the opinions of the fishermen in the Lamu district of Kenya, where the species is still plentiful. The area and the programme of questioning are described. The social life, reproduction, movements and predators of the dugong are recorded as reported by the fishermen. The present distribution is contrasted with the past. My observations on the food plants and their distribution are given, as well as the fishermen's estimation of the part each plays in the dugong's diet. The need for calm water over feeding grounds, afforded by depth of water or shelter from winds, seems to be a controlling factor in the distribution of dugong. Man appears to be the main predator.
 
Article
1. The monthly game counts of Nairobi National Park in 1966 are compared with those of 1961 to 1983 inclusive. It appears that the mean an-nual population of wild ungulates has remained constant at about 4000 animais after a severe decline during the drought of 1961. 2. Wildebeest have continued to decline since the drought and there is no evidence of the former migration to the Athi-Kapiti plains. Reasons for these phenomena are proposed. 3. Kongoni have continued to in-crease since their decline in 1961 and little migration to the plains could be detected in 1966. 4. The mean yearly population of zebra has remained constant since their decline in 1961. At present this is the only species to migrate in large num-bers to and from the plains with the onset and cessation of the rains. 5. Other ungulates were less affected by the drought and their numbers in 1966 appear to have changed relatively little since the beginning of 1961. 6. Females predomInate in the adult populations of all the common plains ungulates. 7. In 1966 lions killed wildebeest at a rate four times greater than would be expected from the percentage of wildebeest in the population. Reasons for this are suggested. As the wildebeest have declined in numbers, the lion have included higher percentages of zebra, warthog, kongoni and eland in their diets.
 
Article
The age and sex structure of the elephant population in Kidepo Valley National Park were studied using recognition files. Moreover, population trends were reviewed using past studies. From 1967 to 2000, the elephant population varied between 200 and 500 individuals. Of the minimum number of 374 elephants found to use the Park, 352 were individually identified. Seventy-nine per cent of these were recorded in 29 families ranging from three to 22 animals with a mean group size of ten. Young animals dominated the population (45% aged 0–9.9 years), while 11% were 10–14.9 years of age and only 18% over 25 years of age. Overall, males constituted 45% of the population, but only 32% of the individuals in the 10–14.9-year age class were males. Individuals ≥15 years of age displayed a skewed sex ratio of 1 : 1.4 in favour of females. The extent of skew was greatest among mature animals (≥25 years of age), which had four times as many females as males. The skewed age structure in the year 2000 caused by poaching and drought, led to a significant difference between the age distribution in 1970 and 2000. Recent counts suggest that the Kidepo elephant population may be increasing.
 
Top-cited authors
Richard F W Barnes
  • University of California, San Diego
Herbert H T Prins
  • Wageningen University & Research
Colin Austin Chapman
  • George Washington University
Lauren J. Chapman
  • McGill University
Iain Douglas-Hamilton
  • University of Oxford