The infamous mopani tree, is a very popular tree in parts of South Africa – not from a tourist perspective, but from occurrence. South Africans are also very anti the tree because they believe that in parts of the Kruger National Park where the mopani dominates, there is no game viewing – this could not be further from the truth.
It’s a fascinating tree, the Latin name is Colophospermum mopane. Colophos comes from colophony, which is a chemical substance, often called rosin. The name colophony comes from the Latin and is named after the city of Colophon (an ancient city in Ionia, in current day Turkey), which was known for producing hardened resin.
Rosin is the residue left over in the making of resin. This part of the name may also be aligned with the strong turpentine smell of the resin, which back in the day was produced, strangely enough, in the city of Colophon. Spermum is the Latin for seed – and so the genus broadly refers to an oily seed. The species name mopane is the Shona for butterfly or moth, because of the shape of the leaf.
There is only one mopane tree in the world, in its genus and specie. It is related to the rooibos tea bush as we know it, and to the pea family – which is very interesting. It is also one of the heaviest woods in South Africa weighing more than a ton per cubic metre, and the tree can grow up to 25m in height!
Hole nesting birds like the hornbill, love mopane woodlands. There is also ‘Mopane manna’ which is picked off the leaves by people and baboons. It is a sweet-tasting, waxy cover on the juvenile stage of a sap-sucking insect known as the mopane psyllid, Arytaina mopani. There is also the tiny mopane bee, Plebina denoita, which many know from its (sometimes successful) attempts at crawling into one’s eyes, ears, and nose in search of moisture. This little bee produces a small amount of edible honey often in the hollow trunks of the tree.
The most significant thing about the tree is that it has a caterpillar, associated with the tree in certain times of the year – in summer. This is called the mopane worm – I think that’s why most people know the tree and why it is ‘famous’.
It is not a very nutrient rich tree, although elephant bulls do feed on it extensively and extract a lot of protein out of it. The cows don’t feed on it too much, especially if they are lactating, because they cannot get enough nutrients out of the tree. But essentially it is used for its high protein source or value. Even the dead leaves on the ground still offer some protein, 40% of the original content, which is amazing. At stages they were even used collectively to feed cattle in certain parts, back in the day.
The tree has incredibly good adaptations to dry, hot climates in that at the base of each bi-foliate leaf (two halves to the leaf), there are small vestiges or organ-like structures that are called a pulvinus or pulvini. So, in the process of photosynthesis when the tree is using solar energy to create a food source (carbohydrates) these pulvini, fill up with liquid and they swell, causing growth independent motor movements in the leaflet and the leaflets effectively close. During hot times of the day, the leaflets close towards each other, and the leaflet therefore has less surface area exposed to the sun, preventing water loss.
The moth associated with the tree is called the mopane moth, Gonimbrasia belina (part of the emperor moth family) – a cream coloured moth, with beautiful eye spots on the underwings that are used for defence. If startled by a predator it will suddenly open its wings revealing the eyespots, which very often startle the would-be predator. It supposedly resembles the eyes of an owl.
If further harassed, the moth has another mechanism for defence – it will just tuck its wings in, and fall to the ground like a leaf, and land amongst the dead leaves on the ground, where it blends in well. The cryptic colouration ensures that it is very camouflaged.
After the first spring rains, the moths crawl out of the ground, and they then lay their eggs on the mopane tree – they are almost exclusively specific to the mopane tree. Eggs are laid, they hatch, and the worms climb out, and they start vigorously feeding on the mopane trees.
The worms grow very quickly. In some years there are so many of them that they eat almost all the leaves on the mopane trees, and it looks like the mopanes are either dead, or lost their leaves again. Essentially though, they are just restimulating the growth in the tree which is key. There could then be spill-over onto other trees for the caterpillars to feed – examples are the marula tree and apple leaf, when there are not sufficient, or no mopane leaves to be eaten.
Once fed, and if they have grown to adulthood, the worms will crawl underground again where they will lay for about 6 months of the year, pupate, and then crawl out as a moth again, in the next spring. The cycle is therefore an egg, larvae, adult and then a pupa – this is the complete life cycle.
The worms are seen in many African countries as a very important source of protein. Once they are harvested, there are different means to eat them; they can be dried out and eaten as a ‘dry crisp’, and they can also be cooked into a broth, like a stew. They do have some economic value as some people sell them, and so there can be a ‘trade’ in worms. The worms are a protein source, as well as stimulating some sort of economic operations.
The worms live for about two months. The moths however have a very short life span, crawling out of the ground, mating and then laying eggs and dying off.
Something else that is quite significant in the Klaserie, about 6 years ago, during a drought, rhino and buffalo were seen browsing on the mopane leaves – eating not only the leaves on the tree but the fallen leaves as well.
This is a very interesting tree that has a whole story associated with it – it’s not to be ignored.
