Browsing Research articles (ORI) by Author "Harris, S."
Now showing items 1-3 of 3
-
Brooks, C.; Bonyongo, C.; Harris, S. (Wildlife Society http://joomla.wildlife.org/index.php?option=com_content&task=view&id=43, NaN, 2008)[more][less]
Abstract: Global Positioning System (GPS) collars are increasingly being used to study fine-scale patterns of animal behavior. Previous studies on GPS collars have tried to determine the causes of location error without attempting to investigate whether the accuracy of fixes provides a correspondingly accurate measure of the animal's natural behavior. When comparing 2 types of GPS collar, we found a significant effect of collar weight and fit on the rate of travel of plains zebra (Equus burchelli antiquorum) females in the Makgadikgadi, Botswana. Although both types of collar were well within accepted norms of collar weight, the slightly heavier collars (0.6% of total body mass [TBM]) reduced rate of travel by >50% when foraging compared with the collar that was 0.4% of TBM. Collar effect was activity specific, particularly interfering with grazing behavior; the effect was less noticeable when zebras crossed larger interpatch distances. We highlight that small differences in collar weight or fit can affect specific behaviors, limiting the extrapolation of fine-scaled GPS data. This has important implications for wildlife biologists, who hitherto have assumed that collars within accepted weight limits have little or no effect on animal movement parameters. URI: http://hdl.handle.net/10311/628 Files in this item: 1
Brooks_JWM_2008.pdf (1.039Mb) -
Bonyongo, M.C.; Harris, S. (Willey Blackwell Publishing http://eu.wiley.com/WileyCDA/Brand/id-35.html, NaN, 2007)[more][less]
Abstract: We used body weight ratio to determine the degree of species-packing of the Okavango Delta (22,000 km2) grazers and compared it to that of four conservation areas of similar sizes but varying in the diversity of habitat types. They are Etosha National Park (23,175 km2) in Namibia, Hwange National Park (14,621 km2) in Zimbabwe, Kafue National Park (24,000 km2) in Zambia and Kruger National Park (19,633 km2) in South Africa. We considered possible ecological explanations for existing gaps within the assemblage. The weight ratio (measure of the degree of species-packing) of the grazers of the Okavango Delta was 1.25, with a total of 27 species which was far less than the theoretically expected 2.0. One-way analysis of covariance (ANCOVA) showed that there were significant differences in the degree of species-packing between the Okavango Delta and other conservation areas of similar size in southern Africa (F1,5 ¼ 166, P < 0.001). Regressing habitat heterogeneity (expressed as number of different habitat types) on species-packing of the five conservation areas yielded a positive linear relationship with R2 ¼ 0.76 implying that 76% of the variation in the degree of speciespacking in the five conservation areas is explained by variation in habitat heterogeneity. We conclude that size ratios are useful descriptors of animal communities and it is a useful measure of species diversity, which can be used for monitoring purposes. Imbalances in weight ratios provide a measure of identifying perturbations due to species loss or arrival of new species within a natural ecosystem. URI: http://hdl.handle.net/10311/608 Files in this item: 1
Bonyongo_AJE_2007.pdf (1.153Mb) -
Bartlam-Brooks, H.; Bonyongo, M.; Harris, S. (Fauna & Flora International, April 7, 2010)[more][less]
Abstract: Terrestrial wildlife migrations, once common, are now rare because of ecosystem fragmentation and uncontrolled hunting. Botswana historically contained migratory populations of many species but habitat fragmentation, especially by fences, has decreased the number and size of many of these populations. During a study investigating herbivore movement patterns in north-west Botswana we recorded a long-distance zebra Equus burchelli antiquorum migration between the Okavango Delta and Makgadikgadi grasslands, a round-trip distance of 588 km; 55% of 11 animals collared in the south-eastern peripheral delta made this journey. This was unexpected as, between 1968 and 2004, the migration could not have followed its present course because of the bisection of the route by a veterinary cordon fence. As little evidence exists to suggest that large-scale movements by medium-sized herbivores can be restored, it is of significant interest that this migration was established to the present highly directed route within 4 years of the fence being removed. The success of wildlife corridors, currently being advocated as the best way to re-establish ecosystem connectivity, relies on animals utilizing novel areas by moving between the connected areas. Our findings suggest that medium-sized herbivores may be able to re-establish migrations relatively quickly once physical barriers have been removed and that the success of future system linkages could be increased by utilizing past migratory routes. URI: http://hdl.handle.net/10311/804 Files in this item: 1
Now showing items 1-3 of 3