Faculty of Natural and Agricultural Sciences
School of Biological Sciences
Department of Zoology and Entomology
Selected Highlights from Research Findings
Movements of humpback whales past North Head, Saldanha Bay, between May 2002 and February 2003 could not readily be divided into separate north and south migrations, and may be affected by high biological productivity in the region (especially in spring and early summer): Resights of at least three individuals in the area after 11-13 years also suggest some fidelity to the area.
Analysis of 'up' (or contact) calls made by southern right whales has shown that those juxtaposed in time and bearing are more similar than other calls, providing the first evidence that the vocalizations of these whales may be individually recognizable.
The longer term effect of biopsying whales has been investigated for the first time, using calving intervals subsequent to the biopsying of 147 cow-calf pairs of right whales in 1996 and 1997: no adverse effects on reproductive output could be detected, although the statistical power was low.
Contact person: Dr PB Best.
The publication of a systematic checklist of the extant mammals of southern Africa represents the first major taxonomic revision of southern Africa since the landmark classification of Meester et al (1986). The revision provides a comprehensive and revised taxonomic framework incorporating many systematic changes over the last 20 years.
Contact person: Prof CT Chimimba.
Studies on foot-and-mouth disease, an economically important disease affecting all artiodactyl species revealed numerous epidemiological insights. The diversity and geographical distribution of topotypes of the SAT2 and SAT3 serotypes of foot-and-mouth disease were described for the first time on a continental scale and complete VP1 gene sequences of SAT1 viruses from West Africa were published. The role of the wildlife maintenance host the African buffalo and other wildlife species in disease transmission was reviewed as was the suitability of currently available vaccines for the control of transboundary diseases.
Technique development for the diagnosis and characterization of African swine fever virus was described. This improved method for the genotyping of field strains of African swine fever virus was applied to over 50 viruses recovered from outbreaks of the disease worldwide and revealed the presence of at least 10 genotypes in the field. This virus diversity is significantly higher than that previously described and has implications for disease control.
Ongoing population studies on African buffalo in the Kruger National Park saw the establishment of 17 microsatellites, with the aim of revealing patterns of migration within the Park. Analyses of the D-loop region of the mitochondrial DNA (mtDNA) genome indicate that the bottleneck caused by the rinderpest pandemic in the late 1800's was less severe than initially described. Together the data suggest that this is a heterogeneous, panmictic population.
Research has shown that buffalo herds are much more dynamic than previously appreciated. Females and subadults often move between herds via splinter groups, and entire herds have dispersed over 40 km. This suggests that males are not solely responsible for transmitting bovine tuberculosis between herds. Modelling results suggest that vaccination is unlikely to be an effective management option due to the high proportion of animals that would need to be vaccinated every year in order to eradicate the disease. Previous analyses of association patterns in fission-fusion societies can be flawed by autocorrelated data and biased results. We developed a new methodology for analysing association patterns in societies like African buffalo. Buffalo herds of higher BTB prevalence lose condition faster and develop higher endoparasite loads during the dry season than herds of lower or zero prevalence.
Contact person: Dr AD Bastos.
All warm-blooded animals need to heat the food they have eaten to their body temperature. This is a real problem for small nectar-feeding birds such as sunbirds or hummingbirds, which must drink large quantities of nectar to obtain their energy requirements. If the nectar is diluted they may consume as much as five times their body mass per day, and on winter mornings the nectar is also very cold. In collaboration with Chris Lotz and Carlos Martinez del Rio at the University of Wyoming a model was developed to investigate the energetic costs of nectar warming and tested on captive rufous hummingbirds. As predicted by the model, metabolic rates of feeding hummingbirds changed dramatically with changes in nectar temperature. Food warming is an important component of the energy budgets of nectar-feeding birds.
Contact person: Prof SW Nicolson.
The development of a novel method that evaluates regeneration success is based on predictable changes in the similarity coefficients of known-aged stages of development of plant and animal groups that represent different levels of ecological integration. The method relies on information on the abundances of species at specific stages of regeneration and control sites (representing the potential end stage of regeneration). Different rates of negative exponential decays in similarity coefficient indicate whether development represents divergence or convergence. These models also provide time frames along which regeneration can be expected. The study is based on 12 years of data collected from eight different groups of plants and animals with support from the Richards Bay Minerals Company and the National Research Foundation.
The Conservation Ecology Research Unit (CERU) assimilated data from satellite images and from the satellite tracking of elephants into a new model, which assesses and predicts the use of landscapes and the dispersal routes of elephants.
The development of a new method to obtain population statistics from free ranging elephants relies on a new model of accurate and precise measures of change in the shoulder heights and back lengths with age. The model is based on measures taken directly and from digital images of free ranging elephants of known age. Through interpolation, ages have now been assigned to individuals in seven populations across southern Africa. Through maximum likelihood approaches and surveys of reproductive data a novel method of determining population growth rates for elephants have been developed. This method is cost-effective and yields results superior to other methods that rely on counting elephants over time.
Contact person: Prof RJ van Aarde.
While previously considered to be broadly sympatric and widely distributed in southern Africa, the medically and agriculturally important cryptic rodent sibling species Aethomys chrysophilus and A. ineptus are now considered to be segregated with a narrow zone of overlap in the northern part of South Africa.
Contact person: Prof CT Chimimba.
Research was initiated in the malaria belt in Mpumalanga to determine the possible role that smaller microchiropterans, and especially the banana bat may play in controlling mosquito numbers. It has been found that on average no more than one male banana bat will be found per furled banana leaf, while female numbers fluctuate from one to seven. Of females 74% are heavily pregnant by the end of October, with 19% lactating. Occupation of new plantations is a very slow process, thereby limiting their distribution.
Contact person: Prof M van der Merwe.
Dawood et al (2002) proposed a molecular phylogeny of the cryptic sand frog genus Tomopterna in Africa based on DNA sequence data. The study used sequence data of a single gene to examine species boundaries in the genus. It resulted in the discovery of three previously undescribed species of which one was described as T. damarensis. This phylogeny was tested using additional gene sequence data, which resulted in the discovery of one further undescribed species in this genus and the phylogenetic placement of the newly described species T. damarensis.
Studies of moss frogs, genus Arthroleptella, of the Western Cape resulted in the description of two new species. The research has contributed to three of the species (A. lightfooti, A. landdrosia and A. drewesii) being proposed for red data listing as near threatened in the 2003 IUCN Red Data list for Amphibians. This genus of frogs continues to excite the general public and Dr Dawood was requested to write a popular article for the Fernkloof Nature Reserve Botanical Society newsletter.
Contact person: Dr A Dawood.
The mole-rat research group made a number of discoveries into the circadian biology of selected species of subterranean rodent moles. The Damaraland mole-rat has been found to possess an endogenous rhythm of melatonin secretion from the pineal, despite the fact that it rarely if ever is exposed to light. The same rhythm can be entrained to a light dark cycle and the rhythm is still expressed under chronic light. Investigation of locomotory activity rhythms revealed that the Damaraland mole-rat has a diurnal rhythm of activity and the highveld mole-rat a nocturnal rhythm of activity. The rhythms free run under constant conditions and can be entrained by light. All available evidence from studies on chronobiology suggests that mole-rats were once above ground dwelling animals that became secondarily subterranean.
Contact person: Prof NC Bennett.
See Research Report Vol 1
Contact person: Prof CH Scholtz.
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