05/26/2023
A mixed Affair
Namibia is home to two species of Zebra, which are Burchell’s plains Zebra (Equus burchellii) and the Hartmann’s mountain Zebra (Equus zebra hartmannae). The most obvious way to tell the difference between the two is by their stripes. The mountain zebra subspecies, Hartmann’s mountain zebra, like the Cape mountain zebra of South Africa, has solid stripes while Burchell’s zebra, seen in abundance on the grasslands of Etosha National Park, has additional faint stripes superimposed on the white and referred to as shadow stripes. On closer observation, it will be noticed that the Hartmann’s zebra stripes don’t join on its stomach and continue down to its hooves, whereas Burchell’s stripes extend onto its underparts and often fade towards its hooves. Sometimes overlapping, the two species favour different habitats. Burchell’s zebra prefers arid savannah with access to water, while Hartmann’s is found in central and southern Namibia in the rugged terrain of the mountain escarpment and adjacent flats.
However, when this overlapping does occur, cross-breeding / hybridization of the two species does happen. This has not only been found to occur between the Burchell’s and Hartmann’s Zebra, but also between the Cape Mountain Zebra, Hartmann’s Zebra and Burchell’s Zebra in South Africa. Additionally, the Greyv’s Zebra and Burchell’s Zebra in east Africa have also been found to cross-breed. The hybridization of these Zebra species might seem to some as not being a problem, but it is a conservation management dilemma. Zebra species such as the Greyv’s are listed as endangered and both the Cape Mountain and Hartmann’s Zebra are listed vulnerable on the IUCN Red list. The hybridization of these species taints the genes of the already protected species.
There are a number of factors that play a role in bringing these two species together and in the hybridization of the different species. Climate change does play a role, but the most common causes are the result of human intervention. Zebra species are unable to move due to fences, artificial waterholes also bring these two species together, habitat fragmentation and the translocation of one species into another species terrain can all play a role in hybridization of the Zebra species. Another possibility is that not enough females are found in the area for the young males, which was one of the cases for the Greyv’s Zebra.
In Namibia, research is currently being conducted by the Ministry of Environment, Forestry and Tourism of the Zebra’s in the western parts of the Etosha National Park. Here the Burchell’s and Hartmann’s Zebra overlap in habitat and where hybridization seems to occur based on the physical attributes of the offspring. It is also not known whether the offspring of these two species is sterile or not, but there is a very high chance of them being fertile as other hybrid species are, such as the Greyv’s and Burchell’s hybrids. Further research is needed to better understand the genetic implications of the hybridization as the Harmann’s Zebra is a protected species and there are approximately only 13 000 individuals left, with the majority being in Namibia (near endemic).
Recently on the live NamibiaCam, a male Hartmann’s Zebra was spotted with a small group of female Burchell’s Zebra at the waterhole. Between them, were two foals and under closer inspection one can see that the foal’s strips are that of a Hartmann’s Zebra. The cause of this hybridization is unclear as the area that they live in has no fences and they can move vast distances. A possible cause behind this is that the male was in search of his own dazzle (a herd of zebra) when he came across the females.
Have a look at the NamibiaCam here: https://www.youtube.com/watch?v=ydYDqZQpim8
