A dissertation submitted to the University of the Witwatersrand in fulfilment of the requirements for the degree of Master of Science in Medicine
Johannesburg 2014 / Animals can shift their orientation to solar radiation to adjust the amount of body surface area that is exposed to solar radiation, thereby manipulating the amount of radiant heat they absorb from their environment. This behaviour is especially important in animals that need to graze out in the open during the day, such as wild ungulates. All previous studies of orientation to solar radiation in animals have relied on visual observations. The problem with visual observations is that animal behaviour, including animal orientation, can be affected by human presence. Therefore I set out to develop a remote technique to detect and quantify orientation to solar radiation in wildebeest to eliminate the need of a human observer. I hypothesised that if an animal was orientated perpendicular to solar radiation, the side facing the sun would be hotter than the opposite side. In contrast, if the animal was orientated parallel to solar radiation I hypothesised that both sides will have a similar temperature.
To test my hypothesis, temperature-sensitive data loggers were implanted subcutaneously into free-ranging black (Connochaetes gnou) and blue wildebeest (Connochaetes taurinus) from Mokala National Park and their orientation to solar radiation was determined visually. I found that when wildebeest were orientated perpendicular to solar radiation, there was a greater difference between the left and right subcutaneous temperature than when wildebeest were orientated parallel to solar radiation (t7=2.5, p=0.04). However, using subcutaneous temperature difference on its own to predict orientation to solar radiation could not account for how the previous orientation to solar radiation of wildebeest affected subcutaneous temperature patterns. Therefore, I designed a prediction model incorporating both subcutaneous temperature difference and rate of change in subcutaneous temperature difference to determine orientation to solar radiation.
The prediction model was accurate more often than expected by chance (60 %), but there were many factors other than solar radiation that influenced subcutaneous temperature, which reduced the accuracy of the remote technique. Further research is necessary to improve the remote technique before it can be successfully used to study orientation to solar radiation. However, my study shows, for the first time, the potential of using subcutaneous temperatures to remotely detect orientation to solar radiation in ungulates. A remote technique to study orientation to solar radiation will be a great advantage for future studies on thermoregulatory behaviour. Because behavioural responses are likely to be an animal’s first defence against increased heat loads resulting from climate change, studying behavioural thermoregulation could provide important information for conservation and management decisions.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/17445 |
| Date | 17 April 2015 |
| Creators | Botha, Arista |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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