Does habitat modification and population size of ice rats (Otomys sloggetti robertsi) contribute to soil erosion in Lesotho?

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dc.contributor.author Mokotjomela, Thabiso Michael
dc.date.accessioned 2008-05-22T12:46:15Z
dc.date.available 2008-05-22T12:46:15Z
dc.date.issued 2008-05-22T12:46:15Z
dc.identifier.uri http://hdl.handle.net/10539/4867
dc.description.abstract Alpine environments are poorly studied ecosystems, largely due to their inaccessibility and severe climatic conditions. Nonetheless, a better understanding is needed of the ecological processes shaping these habitats, particularly the interactions between plants and animals. Recent studies indicate that the levels of soil erosion have increased in parts of Lesotho, possibly because of overgrazing by domestic livestock and the activities of the African ice rat Otomys sloggetti robertsi, whose population numbers have increased in recent times. O. s. robertsi is a diurnal, herbivorous, burrowdwelling, murid rodent, endemic to the southern African Drakensberg. The aim of my study was to establish whether and how the ice rat influences the vegetation and the soil characteristics in its habitat, and to determine whether ice rat population numbers have increased. I conducted three experiments. 1) Enclosures/plots were erected in the Sani Valley to measure the impact of; i) ice rats alone; ii) both ice rats and livestock on vegetation and soil loss and gain (which was used as a proxy for soil erosion). 2) I also ascertained ice rat numbers (colony sizes) at three different locations in Lesotho (Katse Dam, Oxbow and Sani Valley) by conducting monthly censuses of discrete colonies at each locality. 3) Finally, questionnaire surveys were used to ascertain the perception of, and influence on, ice rats by the local human inhabitants in Lesotho. The enclosure/plot experiments showed that the plots accessed by ice rats only had higher levels of vegetation change (loss of cover, decrease in height) and soil movement than other plots from which they were excluded or could access together with livestock, which was contrary to my prediction that the combined influence of ice rats and livestock would have a greater impact. The size of ice rat colonies showed a three-fold increase in my study compared to those a decade ago. The interviews of the local human inhabitants supported this finding, with people also claiming that ambient temperatures had increased and snowfall had decreased. The interviewees did not express any meaningful opinion about how they influenced the biology of ice rats, but claimed that ice rats were responsible for land degradation in the high Drakensberg. In conclusion, the results suggest that ice rats are responsible for large scale damage at my study sites as a result of their foraging and burrowing activities, and erosion is likely to be exacerbated by the increasing numbers of ice rats. Nonetheless, soil erosion is a complex problem involving several biotic and biotic contributing factors, and long term studies are required to fully understand the underlying determinants of erosion in the Lesotho Highlands. en
dc.format.extent 730929 bytes
dc.format.mimetype application/pdf
dc.language.iso en en
dc.subject ice rat en
dc.subject erosion en
dc.subject climate change en
dc.subject livestock en
dc.subject Lesotho en
dc.title Does habitat modification and population size of ice rats (Otomys sloggetti robertsi) contribute to soil erosion in Lesotho? en
dc.type Thesis en


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