While giraffe numbers have plummeted across the African continent in recent years, they are still relatively widely distributed in sub-Saharan Africa. Giraffe are currently and widely recognized as one species and nine (sub)species, based on a combination of distribution, coat pattern, morphology and some genetic data. These subspecies are geographically very distinct. In a recent study, the distribution of two (sub)species that live in close proximity in Namibia, Botswana and South Africa has been further investigated and the results have just been published.
It was always assumed that giraffe populations in northeast Namibia and northern Botswana were Angolan giraffe (G. c. angolensis), while populations further south in Botswana as well as in South Africa were South African giraffe (G. c. giraffa) – see map below for the currently recognised understanding of giraffe distribution in Africa. A recent study undertaken by the Giraffe Conservation Foundation (GCF) in collaboration with scientists of LOEWE Biodiversity and Climate Research Centre (BiK-F) proved these assumptions wrong. Based on their mitochondrial (maternal) DNA, giraffe in northeast Namibia and northern Botswana are actually South African and not Angolan giraffe. This is very surprising, particularly as this means that both subspecies live in close proximity while at the same time showing significant genetic differences.
Today, there are no geographic barriers, such as rivers or mountain ranges, which would inhibit a natural mixing of these two giraffe subspecies. However, between 500,000 and two million years ago, when giraffe split into separate subspecies, the mountain range along the East African Rift System lowered and numerous lakes and other water bodies developed. At the same time, the palaeo-lake Makgadikgadi was at its largest. These water bodies could have separated different populations for a long period of time and could indeed offer an explanation for these recently detected genetic differences. ‘We further assume that female giraffe were more sedentary than their male partners and did not migrate extensive distances. This behaviour would have supported the distinct separation of maternal genetic lines’, explains Friederike Bock, first author of the study.
Impact on Giraffe Conservation
The study shows that there are significant differences in the mitochondrial DNA of these two giraffe subspecies, which has a great impact on conservation and management of these giraffe and others across Africa. A comprehensive understanding of the taxonomy of giraffe and their subspecies as well as their distribution is important to allow for better protecting of specific subspecies. Dr. Julian Fennessy, co-author of this study and Executive Director and Conservation Scientist of the Giraffe Conservation Foundation (GCF) commented on the impact of this study: ‘By having a better understanding of giraffe populations and their genetics, we are able to provide valuable conservation management support to government authorities and wildlife managers throughout Africa. The uniqueness of these two subspecies highlights the need to better understand the taxonomy of all giraffe.’
Bock F, Fennessy J, Bidon T, Tutchings A, Marais A, Deacon F, Janke A. 2014. Mitochondrial sequences reveal a clear separation between Angolan and South African giraffe along a cryptic rift valley. BMC Evolutionary Biology 2014, 14: 219.
The published article can be downloaded here or follow this link to a science blog about the research, which is a bit of a lighter read.
For more information, contact us at GCF directly.
This article originally appeared on the GCF website. It has been reprinted with permission.