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Chemical senses play a critical role in predator-prey and social interactions of many animals. Predators often evoke adaptive escape responses by prey, one of which is the release of chemicals that induce adaptive avoidance behaviors from both predators and conspecifics. I explore the use of chemicals in predator-prey and social interactions, using a crustacean model system, the spiny lobster. As predators, spiny lobsters are opportunistic, polyphagous feeders, and they rely heavily on their chemical senses during feeding. Some of their potential prey deter attacks through chemical defenses that act through the spiny lobsters’ chemical senses. An example of this is sea hares, Aplysia californica, which secrete an ink when vigorously attacked by sympatric spiny lobsters, Panulirus interruptus. I show that that this ink defends sea hares from spiny lobsters through several mechanisms that include phagomimicry, sensory disruption, and deterrence, and that the ink’s efficacy is enhanced by its naturally high acidity. As prey, spiny lobsters rely heavily on their chemical senses to assess risk from predators. One way to assess risk of predation is through ‘alarm cues’, which are injury-related chemicals. I show that injured Caribbean spiny lobsters, Panulirus argus, release alarm cues in their hemolymph, and that nearby conspecifics detect these cues using olfaction. Hemolymph from conspecifics induces primarily alarm behavior in the form of retreat, sheltering, and suppression of appetitive responses. In contrast, hemolymph from heterospecifics, depending on phylogenetic relatedness, induces either mixed alarm and appetitive behaviors or primarily appetitive behaviors. Spiny lobsters also use chemical cues to assess risk during social interactions with conspecific. I show that spiny lobsters use urine-borne chemical signals and agonistic behaviors to communicate social status and that these chemical signals are detected exclusively by the olfactory pathway. Dominant animals increase urine release during social interactions, whereas subordinates do not. Experimental prevention of urine release during interactions causes an increase in agonism, but this increase is abolished when urine of dominants is reintroduced. My findings lay the foundation for neuroethological studies of risk-assessment systems mediated by intraspecific chemical cues.

Thesis (MPhil) -- Stellenbosch University, 2004. / ENGLISH ABSTRACT: Background: Cloning is a topic that has long fascinated people. It has imbedded itself into popular culture, but studies show that the general public has, at best, only a vague understanding of what cloning entails. Alternatively, their perception has been skewed by that very same popular culture. However, cloning is a complex scientific subject that has considerable ethical implications. It is the kind of topic that people in a deliberate democracy should know about. The media play an important role in the education of the public with regards to science and technology. However, the media have the potential to do more than provide the basic facts. In fact, the media can play an important role in influencing the actions and opinions of the public. It is therefore a responsibility of the media to provide accurate information on scientific developments, such as cloning. Objective: An analysis of three daily newspapers in the Western Cape was carried out to determine how cloning is reported. The broad topics addressed were whether the coverage focused on the ethical or scientific aspects of cloning, if the subject was reported in a positive or negative tone, and whether the science of cloning was adequately explained. Methodology: A quantitative content analysis was completed of a sample of 69 articles. These articles were all those relating to cloning that appeared in three daily newspapers (Cape Argus, Cape Times and Die Burger) over a period of one year from 10 November 2002 to 10 November 2003. Findings: Of all the articles analysed 34% focused on the scientific aspects, 21% focused on the ethical aspects, 6% focused on both ethics and science, while 39% focused on neither. Fifty two percent of articles dealing specifically with animal cloning focused on the science, while only 4% focused on the ethics. However, in articles dealing specifically with human cloning, more (30%) emphasised ethical aspects than scientific aspects (20%). With regards to tone of coverage, 32% of all the articles analysed were positive, 28% negative, and 40% neutral. Sixty percent of articles dealing specifically with animal cloning featured a positive tone, while only 13% of articles exclusively about human cloning had a positive tone. This 13% was comprised of articles on therapeutic rather than reproductive cloning. In terms of explaining the science associated with cloning, only 30% of articles provided an explicit explanation. Potential threats to the accuracy of explaining science were found to exist. Conclusions: While the overall findings were somewhat indistinct it seemed that when the media of the Western Cape reported on the cloning of animals it was done with a positive tone and emphasised the scientific aspects. Reporting on human cloning tended to feature a negative tone and emphasised the ethical aspects. The large number of ‘neutral’ results for both the ‘tone’ and 'science or ethics’ variables could indicate that the media were wishing to remain neutral. However, the large number of neutral articles relating to the ‘science or ethics’ variable could have a negative impact on public understanding. The small number of articles explaining cloning and an emphasis on ‘breakthrough’ news stories could also have a negative impact on public understanding. / AFRIKAANSE OPSOMMING: Agtergrond: Kloning is ‘n onderwerp wat die mensdom lank interesseer. Maar selfs al vorm kloning ‘n deel van ons populere kultuur, wys navorsing dat die groot publiek maar vaagweg verstaan wat die onderwerp behels. Dit is ook moontlik dat hul persepsie negatief bemvloed is deur dieselfde populere kultuur. Maar kloning is ‘n komplekse wetenskaplike onderwerp met aansienlike etiese gevolgtrekkings. Dit is ‘n onderwerp waarvan mense in ‘n demokratiese samelewing moet weet. Die media speel ‘n belangrike rol in die groot publiek se opleiding in wetenskap. Maar die media het die potensiaal om meer te doen as net die basiese feite deur te gee. Die media het die potensiaal om die gedrag en menings van die publiek te beTnvloed. Daarom is dit die verantwoordelikheid van die media om akkurate inligting oor wetenskaplike ontwikkelings, soos kloning, te voorsien. Dolewit: Drie daaglikse koerante in die Weskaap is geanaliseer om te bepaal hoe kloning gedek word. Daar is bepaal of die artikels op die etiese of wetenskaplike aspekte van kloning fokus, of die onderwerp in ‘n positiewe of negatiewe toon gedek is, en of die wetenskaplike aspekte doeltreffend verduidelik is. Metode: ‘n Kwantitatiewe inhoudsanalise van 69 artikels is voltooi. Die geanaliseerde artikels is al die oor kloning wat in drie daaglikse koerante (Cape Argus, Cape Times en Die Burger) tussen 10 November 2002 en 10 November 2003 verskyn het. Bevindinge: Van die artikels het 34% net op die wetenskaplike aspekte van kloning gefokus, 21% net op die etiese aspekte, en 6% op beide etiek en wetenskap. Geen van die twee aspekte is in 39% van artikels beklemtoon nie. Van die artikels wat spesifiek oor dierkloning geskryf is, het 52% op die wetenskaplike aspekte gefokus. Net 4% het op die etiese aspekte gefokus. In die geval van artikels oor die kloning van mense, het meer (30%) die etiese aspekte as die wetenskaplike aspekte (20%) beklemtoon. Met betrekking tot die toon, was 32% van al die artikels positief, 28% negatief, en 40% neutraal. In die geval van artikels uitsluitlik oor dierkloning het 60% ‘n positiewe toon gedui, terwyl net 13% van artikels oor menslike kloning in ‘n positiewe toon geskryf was. Die 13% het bestaan uit artikels oor terapeutiese kloning. Geen artikels oor reproduktiewe kloning was met ‘n positiewe toon geskryf nie. Net 30% van artikels het ‘n uitdruklike verduideliking van die geassosieerde wetenskap gegee. Daar is moontlike bedreigings tot die akkuraatheid van wetenskaplike verduidelikings gevind. Gevolgtrekkings: Die algemene bevindinge is ietwat onduidelik maar dit blyk dat die daaglikse koerante van die Weskaap ‘n positiewe toon in hul dekking van dierkloning gebruik het. Die wetenskaplike aspekte van dierkloning was in die artikels beklemtoon. Berigte oor menskloning was in ‘n negatiewe toon geskryf en het die etiese aspekte daarvan beklemtoon. Die groot hoeveelheid ‘neutraal’ resultate vir die ‘toon’ en ‘wetenskap of etiek’ veranderlikes dui moontlik dat die media probeer het om neutraal te bly in hul dekking. Die groot hoeveelheid ‘neutraal’ artikels vir die ‘wetenskap of etiek’ veranderlike kan dalk ‘n negatiewe invloed op publieke begrip van kloning he. Die klein hoeveelheid artikels wat kloning verduidelik, en ‘n klem op ‘deurbraak’ nuusstories kan ook dalk ‘n negatiewe invloed op publieke begrip he.

Thesis (MPhil (Journalism))--University of Stellenbosch, 2008. / Scientists predict that the Western Cape region of South Africa is likely to be one of the regions most affected by climate change. Though the effects on the Cape Floral Kingdom are a huge concern in terms of biodiversity, the effects of climate change are predicted to be far broader than the natural environment. Agriculture, industry, the health sector, politics and the socio-economic sectors among others are all likely to be significantly impacted by climate change in the coming years. The underlying theoretical assumption of the study is that understanding how the climate question has been understood and framed is of vital importance for how the general public will be able to respond to lifestyle changes in aid of climate protection.This study examines the media coverage of climate change over the period of one year in the Western Cape media context, specifically the Cape Times, the Cape Argus and Die Burger. Using a quantitative framing analysis as the central methodology, the study focused on six core frames in analysing all articles relating to climate change. In addition, journalists at the respective newspapers were interviewed to complement the textual analysis. Finally, climate change scientists were interviewed in order to gain their perspectives of the reporting. The study found that the environmental frame was the dominant frame chosen. The political and scientific frames were the next two most prominent frames. It is argued that the dominance of these frames and the comparative lack of reports featuring the human impact frame is problematic as the environment, science and politics are all fairly abstract to the general public.

Includes Van Allen thesis (M.S.)--University of Iowa, 1936, and thesis (Ph.D.)--University of Iowa, 1939.