Observations of gemsbok, Oryx gazella, were made in the Kuiseb River canyon of the Namib Desert. Adults individually contest one another for the right to drink from shallow water wells they dig in the sands of the dry river course. These waterholes are initiated at the dry bottom of open pools after seasonal flooding has passed and the open water dries up. A temporary linear hierarchy is established at each waterhole, allowing adult males to exclude adult females. A combination of flood and water shortage resulted in heavy mortality with a loss of all calves and a disproportionate mortality to adult females during one year of observations.
Welwitschia mirabilis displays certain morphological and physiological features that may be regarded as either gymnospermous or angiospermous. It appears to be a C3/CAM plant, the CAM pathway of photosynthetic CO2 fixation probably having evolved in order to adapt to the extremes of the Namib Desert habitat. The apparent ability to switch from C3 to CAM suggests that Welwitschia originated during a time when more favourable climatic conditions prevailed. And this raises a question: is the Namib Desert not a comparatively young desert? Seen in toto, the many anomalies (eg. gymnospermlike sieve cells, megastrobili, nakedseededness; angiospermlike vessel elements, microstrobili, CAM, mode of chlorophyll formation) confirm the viewpoint that Welwitschia represents an extremeIy specialized endpoint in pIant evolution and that it is not closely related to any extant gymnosperm or angiosperm.
The purpose of this study was to do a (preliminary) survey of the distribution of the species of the genus Aloe in the south of South West Africa. All avaiIable physical and biotic data were collected to compile the distribution map of the various species. The relative density of each of the different species was also determined. A complete background study was made to search for additional information which may help to explain the distribution patterns.
Clarias gariepinus which is an important angling and commercial fish in South West Africa was studied over a period of ten months. This species grows to a larger average size in the Hardap Dam than in most other waters studied.
In the Etosha National Park some 33 000 observations on drinking patterns and behaviour were made on rhinoceros Diceros bicornis, zebra Equus burcheIli, wildebeest Connochaetus taurinus, hartebeest AIcelaphus buselaphus, gemsbok Oryx gazella, kudu Tragelaphus strepsiceros, eland Taurotragus oryx, giraffe Giraffa camelopardalis, warthog Phacochoerus aethiopicus, springbok Antidorcas marsupialis, elephant Loxodonta africana, lion Panthera leo, jackal Canis mesomelas, hyaena Crocuta crocuta and ostrich Struthio camelus. Results were anaIysed and compared with simiIar studies elsewhere and suggest that variations may occur regionally.
13 Blue wildebeest were successfully captured with a standard dose of 2,5 mg etorphine hcl and 20 mg triflupromazine hcl. The narcotic/ tranquillizer mixture was prepared prior to the capture operation thus eliminating the mixing of ""drug-cocktails"" in the field. Diprenorphine hcl effectiveIy antagonised the narcotic effects of etorphine hcl at a ratio of 1:1.
A survey of the carbon isotope composition (13C/12C) of plants in the Central Namib Desert has been undertaken to ascertain the significance of the C-4 photosynthetic pathway to the desert flora. Using this criterion it is found that all the grasses and some sedges are of the C-4 type, while the majority of the other species are C-3. Of the latter group Trianthema, Salsola, Gisekia and Blepheris show the high 13C-content characteristic of ""Kranz"" or strong CAM plants. The C-4 pathway is thus an efficient, but by no means an obligatory adaptive condition for survival in a hot desert environment.
The mineral status of 45 springbok was determined by liver analyses for phosphorus, calcium, magnesium, manganese, zinc, iron and copper. The animals were shot within a period of 14 months on a farm bordering the KaIahari. Mean values of the element concentrations were plotted according to season, and the probable causes of fluctuations are discussed