Rare Sightings of Dwarf Giraffe in Uganda and Namibia
Giraffe – one of our most iconic species. Here we think of them elegantly striding across South Luangwa NP, or ungainly shuffling their long front legs so that they can reach down to a watering hole in order to drink in Mosi-oa-Tunya or Lusaka NPs. But recently researchers from the Giraffe Conservation Foundation have come across two dwarf giraffe in two totally separate countries.
These were not young giraffe, but sub-adult males and are the first dwarf giraffe to have been described in scientific literature. In a recent published paper, Brown and Wells describe how they first spotted a dwarf giraffe in Murchison Falls National Park, Uganda. Observing the young male Nubian giraffe (Giraffa camelopardalis camelopardalis) over two years they found that he had disproportionate limbs in relation to his torso and neck. They next observed a second sub-adult male giraffe, this time an Angolan giraffe (Giraffa giraffa angolensis), on a private game farm in Namibia. He also had apparent disproportionate anatomy.
Using digital photogrammetry techniques, they performed comparative morphometric analyses on these two wild male giraffe. They found that their skeletal dimensions were not consistent with similar aged giraffe of the same species. Both giraffe had shortened metacarpal and radius bones and also exhibited shortened fore-limbs and exhibited different neck lengths. Brown and Wells are uncertain if the etiology of these skeletal aberrations was consistent in both animals.
So why the short legs?
Brown and Wells suggest it is caused by skeletal dysplasias, cartilaginous or skeletal disorders. These sometimes result in abnormal bone development although cases are rarely seen in the wild. Cases of skeletal dysplasia are seen in captive animals, especially when there has been inbreeding with a lack of genetic diversity.
In Murchison Falls National Park the giraffe population is estimated to be >1350 adult individuals. But in the 1980s their population declined to about 78 individuals and they experienced a ‘genetic bottleneck’.
The Ugandan giraffe has not been observed since May 2017 and the Namibian giraffe was last spotted in July last year. Although predation is low in both their habitats, it is thought that they might have succumbed to predation due to their limited mobility caused by having shorter legs. This susceptibility to predators might be another reason why skeletal dysplasias animals are rarely seen in the wild.
What is Genetic Bottleneck?
Genetic bottleneck occurs when a wild animal population is greatly reduced in size, limiting their genetic diversity. This species limitation can be caused by a number of factors, including disease, over hunting, poaching or climate change. Long-term consequences depend on the species, but animal populations with low genetic diversity have less reproductive fitness and a limited ability to adapt to environmental change, with an increased risk of extinction.
Brown and Wells are the first researchers to have documented cases of skeletal dysplasia in two distinct giraffe species in very different geographical locations. You can read their full research paper – Skeletal dysplasia like syndromes in wild giraffe – online at Springer Nature.
Photo Credits: Dr. Michael Brown and Emma Wells