Over the last month the Torchwood trees (Balanites maughamii) have been producing fruit. These small brown fruits can fall from a height of up to 25 m from the top of a tall Torchwood tree and often accumulate at the base. However, when one looks around Londolozi, these trees do not grow in dense stands close together where all of the seeds fall – the trees are usually in isolation, because something is moving them.
The fruits contain a flammable oil (hence the name) and, when ripe, have a particularly foul smell, a smell that I can only compare to old socks. Nevertheless, when they fall to the ground animals relish them – nyalas, kudu and other antelope but elephants in particular. It seems clear that elephants find these small fruits from the ground using their incredible sense of smell. The grasses at the base of a Torchwood tree are often flattened by elephants searching for the fruit, creating large circles around each tree. In fact, s short while ago Amy Attenborough filmed a young elephant bull chasing a herd of impala away from a Torchwood tree! On some occasions, elephants don’t even wait for the fruits to drop to the ground. Bulls in particular walk up to the trunks of these magnificent trees and shake them to gain access to the fruit. Cows and calves seldom do this, but will visit a tree which has been shaken by a bull shortly after he has moved off, in the hope of finding any remaining fruit.
To ensure that they propagate and don’t only grow in one place, some trees need to find ways of dispersing their seeds. Recent studies show that Torchwoods make use of elephants to disperse their seeds. When an elephant chews on these fruits, they can exert an extremely large amount of force onto the hard casing around the fruit, exposing the seed. Smaller animals, like impala, kudu, nyala and even porcupine are only able to chew the sweet fleshy part of the fruit, but can’t exert enough force on the casing to expose the seed. This is where elephants come in. Several studies have shown that seeds that have been chewed by an elephant and pass through its digestive system, have a much better chance of germinating than those which have not. Furthermore, elephants at Londolozi usually have to keep foraging for about 14 hours of their day. In search of food, they can move large distances (depending on the quality of the food available), but typically move between 2 – 4 km (1.2 – 2.5 miles) per day. In addition, when an elephant eats the fruit of a Torchwood, this usually takes about two days to pass through the elephant. The result is that Torchwoods are able to germinate up to 8 km (5.0 miles) away from the parent tree.
There is often a lot more going on than we may see. A bull elephant shaking a Torchwood tree (which may itself have been planted by another elephant) could easily be responsible for the germination of many other Torchwood trees within Londolozi. The dispersal of these seeds is certainly not impossible without elephants, but without them, the distribution of these magnificent trees may then be patchy and genetically similar. It seems there is a unique relationship between these trees and elephants that may have been overlooked for some time.