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We investigated home ranges of grey rhebok and mountain reedbuck at Sterkfontein Dam Nature Reserve in South Africa. Minimum convex polygon (MCP) and adaptive kernel methods were used to estimate home ranges and core areas for six grey rhebok herds and ten territorial male mountain reedbuck. MCP (95%) areas for rhebok herds varied between 30 and 103 ha, while for territorial male mountain reedbuck they varied between 8 and 21 ha. There was <10% home range overlap between any two neighbouring rhebok herds and 5–35% overlap between any two neighbouring territorial male mountain reedbuck. There was complete overlap between the two species indicating no interspecific competitive exclusion. Both species used core areas that coincided with steep slopes. Crude densities were 6.4 rhebok/km2 and 11.5 mountain reedbuck/km2. Rhebok home ranges were smaller in areas with lots of steep slopes, but territorial male mountain reedbuck home ranges were not correlated with any tested ecological parameters. Instead, female occurrence was correlated to steep slopes, and males that held territories with more steep areas had greater access to females.
We characterized the habitat use and movement patterns of adult male, adult female and juvenile Pseudocordylus capensis, a diurnal, rock-dwelling, insectivorous lizard. Rock use was vertically stratified: males spent most of their time at local high points, females at mid-level on the rocks, and juveniles were typically in the lower regions. Movement patterns varied with demographic class as well: juveniles moved more frequently and spent a greater proportion of their time in motion than did adults, and the number of moves of different durations varied among the classes. Finally, juveniles scanned their surroundings and appeared to feed more frequently than adults.
Seasonal floodplains occasionally comprise highly productive zooplankton communities which are exposed to rapid shifts in predator regimes, also between vertebrate and invertebrate predators. We recorded the impact of two co-occurring zooplankton predators, the notonectid Anisops sardea and 0 fish fry of Tilapia rendalli (max gape size 1 mm), on a cladoceran community dominated by Ceriodaphnia reticulata (0.25–0.78 mm), Daphnia laevis (0.6–1.8 mm) and Scapholeberis kingi (0.27–0.8 mm). Both predators strongly reduced abundance of all prey species, yet with a striking size-selective effect for Daphnia prey only, where fish showed a strong preference for small individuals, while Anisops preferred large Daphnia individuals. This contrasts with the general view of size selection in invertebrate versus vertebrate predators, but is logically caused by the feeding mode of the notonectid, and the gape size limitation of the fish fry. The two predators also showed a dietary niche differentiation in terms of both prey selection and habitat choice. T. rendalli fed preferably on small species and size classes, whereas predation from A. sardea concentrated on large prey. Competitive interference was indicated when feeding on Ceriodaphnia, and niche partitioning when feeding on the two other species. The predatory pattern suggests long-lasting coexistence in the system.
Owing to the great similarity in external features between the two cane rat species, Thryonomys swinderianus and T. gregorianus, it is sometimes difficult to distinguish between them, especially when dealing with juveniles and subadults. It becomes even more difficult when trying to identify similar-sized skulls. Additional characteristics of the skull are discussed that may be useful when used along with the original identification key. The presence of a bar across the foramen ovale in the skull of T. gregorianus proved to be the most heuristic. However, because it is not absent in all T. swinderianus skulls, it should be used in combination with the other characteristics.
A qualitative survey of the leaf-litter earthworm fauna of 11 selected indigenous forests in Limpopo Province, South Africa, was conducted to identify the species present, to describe the communities and to assess the relationship between indigenous and exotic species. A total of 8185 individuals from 17 species (five indigenous and 12 exotic species) were recorded. The average earthworm community comprised fewer than five species, but up to seven species were sampled from a single forest. Four of the species recorded are national (one species), regional (one species) or local (two species) endemics. Because these species are not known to live elsewhere, the protection of Limpopo Province forests is critical to their survival. The majority (71%) of the earthworm species sampled was exotic, and differences between exotic and indigenous species richness in forests were mostly significant. At the two spatial scales examined (20 m2 and individual forest) there is no evidence of an association between exotic and indigenous species richness. However, we cannot assume that exotic earthworms do not impact the forest ecosystem.
The mesopredator release hypothesis predicts that reductions in top-predator abundance in a community will increase the abundance or activity of smaller ‘mesopredators’, and increase predation pressure on mesopredator prey, including bird nests. Top predators have been extensively controlled in rangelands managed for sheep in South Africa, because top predators prey on sheep. To test whether this control of top predators has increased nest predation risk for breeding birds in rangeland landscapes, I compared nest predation rates between rangeland areas subject to predator control, and large protected areas with no predator control. An artificial nest experiment found that nest predation by mammalian mesopredators was non-significantly higher in rangeland areas, providing weak support for increased predation by mammalian mesopredators as a consequence of mesopredator release. However, nest predation rates on natural nests of a suite of nine species did not differ between rangeland and protected area landscapes. Thus, control of top predators does not appear to reduce bird nesting success in this system. This result may reflect complex interactions between mammalian mesopredators and other predators of birds' nests, particularly snakes.
The highveld mole-rat, Cryptomys hottentotus pretoriae, is a social bathyergid that exhibits a high reproductive skew and occurs in colonies of between 5 and 14 individuals. Behavioural dominance has previously been assessed in this species using an ordinal ranking procedure and it was found to possess a non-linear dominance hierarchy. The determination of dominance using ordinal ranking is often subjective and cannot deal with ties in rank. This study adapts an objective and robust cardinal assessment method to assign dominance indices to individuals. These indices are then ordered to assign a final rank to each individual within a colony. The non-linear, exponential decay model provided the best fit to data from average cardinal dominance index versus final rank and revealed that colonies contain a single behaviourally-dominant individual. However, final rank could not be predicted on the basis of body mass, sex or assumed reproductive status and is not always statistically significant due to the inherent variation. We propose that the cardinal method of dominance assessment, with the adaptations made in this study, be used in future dominance-related assessments for other bathyergids and social organisms in general.
Cape sugarbirds (Promerops cafer) are the largest nectarivores in the Western Cape and feed almost exclusively on protea nectar and associated arthropods. Helderberg Nature Reserve, Western Cape, South Africa, has a large diversity of Protea and supports breeding sugarbirds. As part of a larger study, we captured sugarbirds using mist-nets during the breeding and non-breeding season at several sites in the Helderberg Nature Reserve, Western Cape, South Africa, from 1996 to 2000. From these data (n = 283 males, 272 females), we found that in both sexes, individuals with longer tails have longer wings. Males were significantly larger in mass, culmen, head, tarsus, wing and tail length than females. Males with larger mass were larger in all morphometric measurements than those with smaller mass. Mate choice and territory defence may be based on wing and tail ornament displays of male sugarbirds, thus larger males with larger ornaments could benefit through greater breeding success than smaller males.
Although savanna is one of the most important biomes in southern Africa, it is, apart from the botanical component, one of the least studied. This study aimed to document the distribution patterns, richness and diversity of selected ground-dwelling, flightless arthropods (millipedes, centipedes and scorpions) within savanna habitats to improve invertebrate conservation planning. Five habitat types (white sand bushveld, brown sand bushveld, general mixed bushveld, rocky outcrops and mopane woodland) within the Greater Makalali Conservancy, Limpopo Province, South Africa, were studied using four successful sampling methods (active searching of two types of quadrats, pitfall traps and drive transects) during three sampling periods between February 1999 and March 2000. Millipedes were consistently the most species rich and abundant taxon. Species were not uniformly distributed across all habitat types; some species were unique to certain habitats. Generally, the more heterogeneous habitats supported the greatest millipede, centipede and scorpion diversity, richness and density, and in the case of the millipedes contained the highest number of regional endemics and habitat specialists. There was no significant difference in scorpion diversity among habitats.
Twenty-four years (1977–2000) of competitive shore angling catch and effort data from the KwaZulu-Natal Coastal Anglers Union for the province of KwaZulu-Natal were analysed. Of a minimum of 117 species recorded, the most commonly caught species were dusky shark (Carcharhinus obscurus) (26%), milk shark (Rhizoprionodon acutus) (18%) and shad (Pomatomus saltatrix) (10%). By weight, the top species were dusky shark (34%) and diamond ray (Gymnura natalensis) (19%). All the above species showed considerable inter-annual variation in their respective contributions to annual catch. Probably as a result of changes in fishing patterns, dusky shark and milk shark showed a general decline in percentage contribution to catch over the period, while contributions of lesser guitarfish (Rhinobatos annulatus), giant guitarfish (Rhynchobatus djiddensis), diamond ray (Gymnura natalensis) and brown ray (Himantura gerrardi) increased. Mean overall annual cpue by number and weight showed a non-significant increase over the period, while each of the investigated species showed a constant trend in mean annual weight. There were high proportions of juveniles in the catches of dusky shark (100%), dusky kob (92%) and giant guitarfish (78%). Improvements made to the structure of shore angling competitions and the overall contribution of competition angling to resource management in South Africa is discussed.
The Molossidae bat Mops midas has a broad distribution across portions of Africa and is also known from Madagascar. The African populations have been referred to the subspecies M. m. midas and those from Madagascar to M. m. miarensis. The subspecific differences between these two forms have been called into question. However, largely due to the rarity of the Malagasy subspecies in collections, it has not been previously possible to address this point. Recent bat surveys on Madagascar have found that this species is relatively common in portions of the west and south; using these new collections, we address the question of the distinctiveness of miarensis. External measurements and soft-part anatomy, as well as cranial and dental measurements and structure, revealed few differences between the African and Malagasy populations. Further, molecular comparisons using 1080 bp of mitochondrial cytochrome b found a divergence of only 0.1% between South African and Malagasy populations, compared with a divergence of 13.3/13.5% between them and M. condylurus/M. leucostigma. Further, comparisons of 304 bp of the more variable mitochondrial d-loop revealed a divergence of only 1.2% between South African and Malagasy M. midas, compared with a divergence of 40.9/42.3% between them and M. condylurus/M. leucostigma. Consequently, we propose that no subspecific variation should be recognized in M. midas. A biogeographic analysis is presented with regards to movements of molossid bats between portions of eastern and southern Africa and Madagascar.
The karyotypes of three species of yellowfish, namely Labeobarbus marequensis (A. Smith, 1841), L. capensis (A. Smith, 1841) and L. polylepis (Boulenger, 1907), were examined by Giemsa staining using an approach improved for the description of high chromosome numbers. In each case, 2n = 150; no heteromorphic chromosomes were detected; chromosomes in all morphological categories ranged smoothly from large to small, with no distinctly large submetacentric pairs; and metacentric chromosomes showed little variation in size. Labeobarbus marequensis had 26 metacentric (m), 44 submetacentric (sm), 42 subtelocentric (st) and 38 acrocentric (a) chromosomes and a fundamental number (FN) of 262; L. capensis had 16 m, 58 sm, 42 st and 34 a chromosomes and FN = 266; and L. polylepis had 18 m, 60 sm, 42 st and 30 a chromosomes and FN = 270. These results, combined with published literature, imply that Labeobarbus Rüppel, 1836 is an evolutionarily hexaploid African lineage and support its removal from synonymy with the evolutionarily tetraploid Asian genus Tor Gray, 1834. A review of fundamental numbers for conspecific Labeobarbus species examined in different studies implicated karyological technique as a confounding factor in assessing details of karyotypes, leading to recommendations for future karyological studies of barbine fishes. Potential synapomorphies are pointed out in karyological characters of species within Labeobarbus.
A survey of bushbuck was carried out along the Chobe riverfront, Chobe National Park, Botswana. We used road counts, as was done in previous surveys in the Park, in order to reveal trends in population size over time. As the animals could be individually recognized, the absolute population size could be calculated using capture-recapture technique. We estimated the population along the c. 50 km of riverfront in the Park to be 39 animals (standard deviation 7.47). To our knowledge this is the first objective estimate of the bushbuck population in the area. Comparing numbers of bushbuck observed from different survey periods to reveal trends over time proved difficult except in very general terms. There is, however, evidence that the population has undergone considerable variation with changes in woody vegetation density and that it was low about 1900, peaked in the 1960s and then declined to the 1990s. There is no evidence for a further decline between 1991 and our study.
We present the results of a chromosomal study (C-, Ag-NOR-, endonuclease digestion, DAPI and CMA3 banding) carried out on four Tunisian species of amphibians: Bufo mauritanicus, B. viridis, Rana saharica and Discoglossus pictus auritus. For comparative purposes, our cytogenetic analysis was also extended to Moroccan specimens of B. mauritanicus and D. pictus scovazzi. Tunisian specimens of B. viridis display chromosome and chromatin characters very similar to those found in other specimens, both North African and Euro-Asian. By contrast, chromosomes of Tunisian specimens of B. mauritanicus differed from the Moroccan specimens in presenting a different Q-banding phenotype. Tunisian specimens of R. saharica displayed the plesiomorphic Pelophylax karyotype of 2n = 26 biarmed chromosomes and NORs on the eleventh pair. The Tunisian specimens of D. pictus auritus had the typical D. pictus 2n = 28 karyotype with the 13th pair of telocentric elements, in contrast to the Spanish auritus specimens that display the chromosomes of this pair shaped as metacentric. Similarities and differences of the four studied Tunisians anuran taxa are discussed with references to published data on their relatives.
Pseudodactylogyrus anguillae is a monogenean parasite of anguillid eels that is thought to have Pacific origins. Recent identification of Pseudodactylogyrus in Europe and America has been attributed to human-mediated introductions. Here we report the first confirmed incidence of P. anguillae in South Africa and discuss whether it is a natural parasite of South African eels or an introduced exotic.
A new species of Streptaxidae, Gulella obani, is described from southeastern Nigeria. On account of its apical sculpture, which is spirally and vertically striate, long angular lamella and presence of a basal denticle the new species is placed in the subgenus Tortigulella Pilsbry.
The reproductive cycle of the Namibian striped skink is described from a histological examination of gonadal material from museum specimens. Males followed a seasonal testicular cycle in which sperm were produced primarily during spring and summer. Testes in regression were present mainly in March. Females with oviductal eggs or corpora lutea were present September to March and May to June. Not all females reproduced annually. Clutch (= litter size) for 23 females was 4.9 ± 0.97 S.D., range: 3–6.
Rodents are of concern as reservoirs and transmitters of pathogens that cause zoonotic and other diseases in domestic animals and humans. The contact between wild and urban rodent fauna is increasing in expanding cities in Africa, and this arguably increases the risk of disease transmission to urban populations. When rodents from rural areas are accidentally introduced into cities and encounter urban rodents, for example, in markets, grain mills and butcheries, there is a potential that pathogens are transferred between rural and urban rodent populations. Using a non-toxic biomarker, Rhodamine B (RB), we investigated the distances over which rodents are active around such potential introduction sites. Animals feeding at such sites were traced up to 100 m distant within a period of 10 days. We found that RB is a practical alternative for studying rodent movements. These results may be useful in designing management strategies to reduce the risk of the introduction of new rodent-borne pathogens in cities.
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