Parallel A: Feeding Ecology

The phenology of plants is known to influence the availability of food to browser game species, and ultimately their habitat selection and diet preferences. Phenology studies on woody plants done in the central and eastern regions of South Africa further highlighted the effect of phenology on browse availability and plant palatability. In the highly seasonal semi-arid environments of the Northern Cape Province of South Africa, the phenology of woody plants is expected to play an even greater role in food availability and palatability due to distinct wet and dry seasons and large temperature variations between summer and winter. To determine the potential impact of phenology on browse availability in a semi-arid environment, the phenology of twenty abundant woody plant species of the South-eastern Kalahari was studied in the Witsand Nature Reserve. A total of 10 - 30 individual plants representative of the population of each of the studied woody species were marked and inspected monthly. During each inspection, plants were allocated a leaf carriage score and leaves classified into different phenophases (budding leaves, young green leaves, mature green leaves, yellowing leaves and dry leaves still attached to the plant). The presence of flowers and fruits or pods were also recorded. Mean monthly leaf carriage scores were calculated and changes in phenophases of species over a year cycle determined. Strong seasonal influences on plant phenology were observed, especially in the case of the winter deciduous woody species. Most of the winter deciduous species started dropping leaves with the onset of the early dry season (May) and were largely leafless throughout the late dry season (Aug-Nov). Two regional dominant species, Senegalia mellifera (Black thorn) and Rhigozum trichotomum (Three thorn), were found to flush new leaves only as late as mid-December. The results highlighted the importance of palatable evergreen species such as Boscia albitrunca (Shepherd’s tree), Vachellia haematoxylon (Grey camel thorn) and Vachellia erioloba (Camel thorn) as a food source during the late dry season. Where these evergreen species occur in low densities, the time of flowering and availability of pods/fruit may be crucial for game species to bridge this critical period. The implications of seasonal plant phenology changes on the management of browser game species in the semi-arid Northern Cape are discussed.

Leafhoppers are small jumping and flying insects with sucking mouthparts. Immature stages hatch from eggs inserted into plant tissue and resemble adults without wings, but that grow larger after every moult. Their sap-sucking habit, in phloem, xylem or superficial cells, means they are not noticed as easily as chewing insects such as grasshoppers, caterpillars, beetles or termites, and have the potential to transmit plant bacteria and viruses. Much is known about the grass-living insects of the Savanna biome through various studies, such as surveys of the grasshopper fauna of Nylsvlei and grasshoppers as grassland indicators. Some studies in the Drakensberg have examined the recolonization of invertebrates after fire. Leafhoppers are the most species rich group of the Heteroptera estimated at 700 species from records in the National Collection of Insects. Species are classified mainly by the structure of the male sex organ, and females often are only recognized by association with males while nymphs, are usually also difficult to associate. Pheromones and ultrasound play an important role in the communication between adults. The aim of this study is to use leafhoppers endemic to the Grassland or wide-spread in the Savanna Biome as an indication of biodiversity and habitat conditions, such as grazing and burning. Methods to collect leafhoppers include the sweep net, a strong net on a short stick to sweep through grass and shrubs and vacuum machines, but also pan traps, sticky traps, malaise traps, intercept traps, sometimes pitfall traps, although the latter do not directly reflect an associated plant. Fogging is also suitable for leafhoppers and plant associations. Qualitative sampling of leafhoppers and associated feeding plants produced museum based specimens and supplemented by fieldwork. Curation required sorting, card pointing and pinning representatives, labelling, identification and accession. Systematic work has revealed 110 species in 40 genera in the Savanna, and 70 species in 14 genera in the Grassland Biome. This is a conservative estimate that excludes the leafhoppers that feed on superficial plant tissue, the Typhlocybinae. Savanna leafhoppers are generally long-winged, suggesting migratory behaviour and are wide-spread Afrotropical distribution and are expected to colonise regrowth in burned habitats. Most Grassland Biome leafhoppers are short-winged and thus unable or slow to recolonise regrowth in burned or overgrazed habitats. One species thrives on unpalatable species of Merxmuellera in the Eastern Cape Province. Leafhoppers with tree or shrub associations such as Boscia, Galenia and Pentzia has started recently. Many species were described from the Fynbos Biome mainly on shrubs, but many more require systematic work, with even more in the other biomes. Some leafhoppers appear to follow floristic links between the Fynbos and Grassland biomes, and even seem to show speciation in floristic centers of endemism. Thus high numbers of species and large population size despite small size of specimens, make leafhoppers a suitable group to study rangeland or grassland biodiversity.