By Katherine King, of Colby College
A classic in the delta, Mopane trees (Colophospermum mopane) were the very first we learned to identify in Botswana and have been by far, the most commonly seen during our time here. When we arrived during the dry season, the only sense of these trees we got was their rough, light brown bark and brown, dried leaves shaped like the wings of a butterfly. As the semester progressed, we were able to witness these trees seemingly coming back to life with the arrival of the rains in late October and November. Small buds sprouting from what appeared to be dead mopane shrubs quickly grew into the large leaves, some as big as 10 cm long, that now create a bush so thick in some areas it is difficult to spot even the largest animals on our transect drives. While mopane trees do very well in the wet season in the delta, they are also very successful in the dry alluvial soils of the delta (Okavango Field Guide, Gutteridge & Reumerman). Their long roots allow them to remain stable enough to grow tall and reach the low water table in the dry season. Their wing shaped leaves also allow them to prevent water loss through transpiration on hot days by folding together and decreasing the surface area of the leaf exposed to the sun (Okavango Field Guide, Gutteridge & Reumerman).
Wing shaped leaves on the mopane tree
While we lament over the decreased visibility, we are not alone in welcoming the lush greenness these new leaves have added to the landscape. Elephants (Loxodonta africana), especially, enjoy the new mopane growth and we often see them grazing in various mopane habitats, whether it be mostly scrubs of about 5m or- mature mopane woodlands with trees around 15m tall. Elephants also enjoy eating mopane branches in the dry season when vegetation is limited. In order to reach the taller trees, they will often knock down the trees to reach the upper leaves and branches. The role of elephants as ecosystem engineers is particularly influential for the kind of mopane habitats that we have seen. Areas that clearly have more destruction by elephants tend to consist mostly of shorter mopane scrubs while other, less disturbed areas, have taller, more mature mopane trees present.
Finding elephants in the thick mopane scrub after the rains.
Not only are mopane very useful for the wildlife in the delta, but Sixteen has also told us about several traditional uses of mopane. Mopane wood is known to be very good for building and is often used in the construction of many traditional homes in the area. The wood also makes particularly good firewood that produces long lasting embers and heat that are very good for cooking over the fire. Mopane trees are also used by the emperor moth (Saturnia pavonia) to lay their eggs for hatching. When the eggs hatch, the so-called Mopane Worms, spend their days munching on the mopane gum until it is time for metamorphosis. When the emperor moth emerges, the wing shaped leaves provide the perfect sitting spot for the wings to unfold. Until then, however, local people utilize these worms for a snack. A delicacy around the delta, the mopane worms can be eaten fried or dried, depending on your preference.