Vegetation ecology of the seasonal floodplains in the Okavango Delta, Botswana

Please read the abstract in the 08summary part of this documentDissertation (MSc (Botany))--University of Pretoria, 2007.Plant Scienceunrestricte

The ecology of large herbivores in the Okavango Delta, Botswana

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Data from: Behaviour-related scalar habitat use by Cape buffalo (Syncerus caffer caffer)

Studies of habitat use by animals must consider behavioural resource requirements at different scales, which could influence the functional value of different sites. Using Cape buffalo (Syncerus caffer caffer) in the Okavango Delta, Botswana, we tested the hypotheses that behaviour affected use between and within habitats, hereafter referred to as macro- and microhabitats, respectively. We fitted GPS-enabled collars to fifteen buffalo and used the distances and turning angles between consecutive fixes to cluster the resulting data into resting, grazing, walking and relocating behaviours. Distance to water and six vegetation characteristic variables were recorded in sites used for each behaviour, except for relocating, which occurred too infrequently. We used multilevel logistic regressions to identify variables that characterised macro- and microhabitats. Our results showed that macrohabitat use was linked to behaviour, although this was least apparent during the rainy season, when resources were most abundant. Behaviour-related microhabitat use was less significant, but variation in forage characteristics could predict behaviour within all macrohabitats. The variables predicting behaviour were not consistent, but resting and grazing sites were more readily identifiable than walking sites, highlighting the importance of resting, as well as foraging, site availability in buffalo spatial processes. Our results emphasise the importance of considering several behaviours and scales in studies of habitat use to understand the links between environmental resources and animal behavioural and spatial ecology

Data from: Effects of divergent migratory strategies on access to resources for Cape buffalo (Syncerus caffer caffer)

Populations of large herbivores frequently display divergent migratory strategies, a likely consequence of the trade-off between the costs and benefits of migration. Globally, physical and environmental barriers disrupt migrations, leading to increased residency, which can have detrimental consequences. In the Okavango Delta, Botswana, veterinary cordon fences erected in 1982 may have caused enforced residency in some subpopulations of Cape buffalo (Syncerus caffer caffer). We used data from GPS-enabled collars fitted to females in 1 resident and 1 migratory subpopulation of buffalo to test the hypotheses that 1) residents have access to less-productive forage than migrants, 2) residents occupy smaller home ranges and live in smaller herds than migrants, 3) reproductive productivity is lower in resident herds, and 4) residents have poorer body condition than migrants. Forage characteristics varied between resident and migrant ranges, both between and within seasons. Reproductive productivity and body condition did not differ between subpopulations, but residents occupied smaller home ranges during the rainy season and lived in smaller herds than migrants. Enforced residency could have decreased carrying capacity when the fence was erected, so resident buffalo may have adapted by forming smaller herds, allowing them to maintain their body condition. The area that residents occupied was located in a more central region of the Okavango Delta than that of migrants; therefore, this area would receive higher levels of nutrients from the annual flood, which would have increased heterogeneity in resident ranges, potentially compensating for effects of disrupted migrations. These results highlight the importance of conserving landscapes with spatially and temporally heterogeneous resources to buffer effects of anthropogenic activities such as artificial barriers on migrations

Variables discriminating between microhabitats used for different behaviours during the early flood season.

<p>Values marked with (#) and (*) were significantly and not significantly different from each other, respectively.</p

Criteria used for determining body condition scores.

<p>Criteria used for determining body condition scores.</p

Mean body condition scores of buffalo during the 2008 and 2009 late flood seasons.

<p>Error bars represent one standard deviation.</p

Behaviour data

Proportional behaviour in macrohabitats and different season

Example of a utilisation distribution produced using the Movement Density Kernel Estimation method.

<p>The figure is based on 1754 GPS fixes from one collared buffalo, B5, during the rainy season of 2009.</p

Seasonal second and third order habitat selection ratios and confidence intervals.

<p>Ratios with 95% confidence intervals that did not include 1 indicated selection (>1) or avoidance (<1) of particular habitat types. Significant results are shown in bold. Second order selection compared habitat use in individual MCP ranges to availability in the population range; third order selection compared habitat use in the utilisation distributions to availability in the individual MCPs.</p