Botswana National Museum, in Botswana's capital city of Gabarone, manages Tsodilo Hills--a national park in the country's rugged, northwest desert--=to preserve cave paintings and human habitations dating to the Late Stone Age. The park is a UNESCO World Heritage Site. The hills tower above surrounding Kalahari plain grassland, growing over stabilized sand dunes.
Among hundreds of Tsodilo plants gathered and eaten by today's Bushmen in the area, Ricinodendron rautaneii (Mongongo), a Euphorbe, supplies 30 percent of their nutrition. Mongongo reaches 36 feet and flowers creamy white at age 25.
Mongongo produces plum-like fruit with tough fuzzy skin over spongy flesh. Fruit falls April to May (autumn dry season) and ripens, but some fruit ripens on the tree until August. The flesh resembles dates and is stored dry or boiled to sauce. Kernels are eaten raw or roasted and taste like cashews.
Citrullus lanatus (Tsama melon) grows rapidly in the rainy season, producing watermelon-like fruits that mature in the cold-dry season (May to August). Their 90 percent water content sustains humans and wildlife. The round fruits are the size of commercial cantaloupe, with a green rind striped with splotches of lighter green. Bushmen open fruit at the stem with a stick, using the rind as a container. The flesh is pounded to liquid inside the rind and sucked out. The seeds are roasted.
Acanthosicyos naudinianus (Gemsbok melon) is a trailing vine that arises from its 3-foot-long, bitter, perennial tuber in the rainy season. Gemsbok is a water source for humans and wildlife. Foliage resembles asparagus but is actually a Cucurbit. Immature fruit are blue-green and burn the tongue when eaten. Fruits mature to a yellow color in the dry season and appear orange when overripe. Fruit skin is knobby and spined. Gemsbok is eaten raw or roasted in embers and pounded to gruel.
Berries of Ochna pulchra and Grewia flava (Velvet Raisin) ripen just after rainy season begins. Ochna pulchra tree reaches 24 feet with a spreading crown. Outer bark peels in sheets from the trunk. Each yellow flower yields a green drupe protected by red sepals. Mature fruit is black, but bushmen also roast and eat the green fruit. Grewia flava is a 6-foot shrub that bears reddish-brown fruits that ripen in February.
The Strychnos cocculoides (monkey orange) tree reaches 15 feet tall and is covered with half-inch thorns. Deep roots develop before the tree gains height. The fruits ripen in the dry season, but unripe fruits are collected and buried to hurry ripening and protect them from insects. Monkey orange is the size and color of commercial oranges but is unrelated. The orange shell is woody and contains many seeds, each inside the membrane of an edible pulp.