By Anna Nisi (Carleton College)
Acacia erioloba, Mogothlo (Setswana)
“Camelthorn” is a direct translation of Afrikaans “Kameldoring”, which means Acacia of the giraffe (the scientific name for giraffe is Giraffa camelopardalis). Camelthorns can reach 17m in height with rounded canopies, although they can also be shrublike when smaller. Camelthorns have blue green foliage with alternate bipinnate leaves. Branches are zigzagged and have long, straight, white thorns at the elbows that can be up to 5 cm long and get stuck in your shoes and puncture our tires. Branches are angular and often look “untidy”. Camelthorns produce yellow, circular puff-ball flowers and large ear-shaped brown-grey seed pods.
A. erioloba is in the Leguminosae family, and as a legume harbors symbiotic Rhizobia bacteria in root nodules that are able to fix nitrogen. As nitrogen fixers, camelthorns and other acacias have high nitrogen (protein) content compared to other plants and produce highly nutritional forage. They are a preferred food source for many browsers – their leaves are favored by giraffes, which amazingly are able to navigate around the thorns. Seed pods are also highly preferred, with high phosphorous, protein, and fat contents. Elephants will shake camelthorns causing pods to fall to the ground and then eat all the pods. Animals such as kori bustards, bushbabies, and tree rats also eat gum from wound spots.
Camelthorns are able to survive in dry or arid environments such as the Kalahari sandvelt because they send down a long tap root that reaches the water table (maximum recorded length: 46m in Namibia). They are deciduous trees and only lose their leaves for a short period of time. They are one of the first species to grow new leaves in the spring, contributing to their importance as a food source for many animals when other forage is scarce. They are also important shade trees. Additionally, their ability to fix nitrogen causes an increase in soil nitrogen content as camelthorn biomass is returned to the soil. This can lead to increased growth of grasses, which attracts grazers and other game.
Camelthorn leaves can sometimes be toxic. During drought or other stressful conditions, their leaves produce high amounts of cyanogenetic glucosides. Ruminant grazers produce an enzyme that breaks down these glucosides into cyanic acid (HCN), which prevents oxygen absorption into body cells – this is known as prussic acid poisoning.
In the late 1950s and early 1960s, camelthorns were thought to be a good habitat for the tsetse fly, whose eradication was being attempted due to their role in spreading sleeping sickness. Eradication was also attempted for the camelthorn and many trees were cleared, but this effort was abandoned in 1966 and camelthorn populations have mainly recovered.
Camelthorns are extremely common trees and we see them every day, often with a lot of wildlife hanging out under their shade to beat the mid-day heat. Yesterday, we saw Hector (our favorite male lion) hanging out under a camelthorn to get out of the sun.
Acacia erioloba flowering in September (Photo: Susie Dain-Owens)
FUN FACTS
Seeds can be roasted and prepared like coffee
Wood is termite resistant!
Medicinal uses include headaches and earaches
Some tribes regard camelthorns as sacred, or have special rules about their use. For example, in some tribes only chiefs are allowed to fell a camelthorn.
If you take refuge in a camelthorn during wartime, it is believed you will be protected from enemies and wild animals. However, I don’t know how you would navigate around the thorns.
Water color by Anna Nisi