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The CKGR

The Central Kalahari is a unique, beautiful place, situated in the middle of the kalahari sands.

The Kalahari sands (beige), Botswana (Black line), the Kalahari Lion Conservation Unit (red line), the CKGR (Dark green area) and the study are for this project (light green area).

The Kalahari sands (beige), Botswana (Black line), the Kalahari Lion Conservation Unit (red line), the CKGR (Dark green area) and the study are for this project (light green area).

 

PreyRoutes

A schematic of the lion prey survey route taken every month

Pan Habitats

A distinctive feature of the CKGR is the pan habitats. Many roads run through pans, and campsites are usally close by. They  consist of a hard clay base in a flat depression. The pans provide exceptional grazing for some species, even though the grass is usually short. Nutrients like calcium and phosphorous are presumed to be abundant and sought by grazing herbivores.

 

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Pans mostly comprise well-grazed Schmidtia kalahariensis grasses and a variety of forbs (families Acanthaceae, Asteraceae, Amaranthaceae, Aizoaceae and Scrophularaceae), with the occasional tall tree (see habitat categories below for examples of species). Pan habitats are preferred by grazing herbivores for much of the year for high nutrient grasses and provision of salt licks (Williamson et al. 1988). They frequently contain shallow depressions that collect water in the rainy season and last for variable periods into the dry season. Pans usually have calcium tolerant plants at the ecotone boundary to sandy habitats. These plants include Cataphractes alexandri and Vachellia nebrownii.  These shrubs only occasionally cover entire, small pans. I used Landsat 5 satellite imagery (USGS, 2010) and compared to direct ground measurement to estimate the coverage of pan type habitats at approximately 2.8% of the study area.

Dune savannah habitat

The most abundant habitat is the dune savannah.  This habitat is built on soft sand that formed sand dunes in drier times. Now vegetation stops most movement of the dunes, but they are still very visible features. Grass grows tall on this sandy substrate, and woody shrubs are very common. Gemsbok (a common southern african Oryx species) are abundant here, although widely dispersed in small groups. The lions do most of their hunting in this habitat which provides them good cover, and Gemsbok are a favoured species.

 

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Dune savannah or mixed shrub savannah (Dawson and Butynski, 1975) are open grassy habitats on a sandy substrate with varying levels of shrubs, dominated by the grasses Cenchrus ciliaris, Digitaria eriantha, Stipagrostis uniplumis and Panicum spp.  Shrubs include Lonchocarpus nelsii, Terminalia sericea, Cataphractes alexandri, Bauhinia petersiana, Senegalia mellifera detinens, Senegalia fleckii, Grewia flava, G. bicolor, G. flavescens, Dichrostachys cinerea, Vachellia nebrownii, Senegalia ataxacantha, Boscia albitrunca, V. hebeclada, V. erioloba, and V sieberiana. This habitat is favoured by fine grained substrates, deeper bedrocks, and lower rainfall than woodland habitats (Moore and Attwell, 1999). I had originally intended to classify this varied habitat into sub-categories to capture density and heights of shrubs within, however the algorithms employed to categorise the remotely sensed images were unable to distinguish sufficient differences along the subtle spectrum, and field categorization was similarly difficult.

 

 

Woodlands

Woodlands are uncommon in the CKGR, and unimpressive.

 

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Woodland habitat is found mostly in the north-east of the study area between and to the east of Leopard Pan and Sunday Pan and is a result of coarser grain, shallow depth to bedrock and higher rainfall. The predominant tree types are Terminalia prunioides, T. sericea, Albizia anthelmintica, Vachellia erioloba and Combretum imberbe.  These trees are also found in much sparser numbers occasionally through the all of the other habitat types. I defined the woodlands (greater than 30% tree canopy cover) that is considered separately by other authors (e.g. (Moore and Attwell, 1999)) but is a rare habitat and insufficient herbivore counts made estimating density separately for woodlands problematic. As a relatively closed habitat it is difficult to photograph; the scale of the trees are similar to those in the slideshow photo of the pans.