While conducting a photographic survey of the giraffe population in Murchison Falls National Park, Uganda, a group of researchers spotted something unusual. One of the wild giraffes looked a little different from the others, with notably shorter legs despite having what appeared to be a sub-adult body size. Then, while carrying out similar work in Namibia, they spotted a second wild giraffe with similar morphological abnormalities.
Giraffe calves fully mature somewhere between three and six years of age, and this second giraffe was thought to be born in 2014, meaning this individual should exhibit the leg lengths of an adult. The researchers believe both giraffes are affected by a condition similar to skeletal dysplasia (an umbrella term for conditions that affect limb length including dwarfism). Their paper, in the journal BMC Research Notes, is the first to describe giraffes with this condition found in the wild.
Before diving into why these animals developed differently to their fully grown giraffe friends, it’s perhaps best to first touch on how you go about measuring a giraffe. With an average height of 4.6 to 6.1 meters (15.1 to 20 feet), it’s no easy task for a comparatively small human with a measuring tape. It’s also important when conducting research on wild animals that such data collection is non-invasive as disrupting these animals could have negative consequences for their behavior or survival.
To overcome this, a method was developed for measuring elephants called photogrammetry. The technique uses a laser rangefinder to measure the distance between features of interest. By gauging the distance between digital pixels in the photo and comparing them to the actual size of the focal feature they can provide accurate measurements from photographs of large animals, including giraffes.
By comparing this morphometric data, the researchers were able to establish that the two giraffes that appeared unusually short were indeed significantly different from the average heights of each population of giraffes. The giraffe in Uganda had a phalanx (the lowermost segment of the leg) that was roughly the same length as its buddies’, but this part of the leg on the Namibian giraffe was significantly shortened, each measuring 21.2 centimeters (8.3 inches) and 15.8 centimeters (6.2 inches) respectively. Both animals had metacarpal and radial measurements below the average.
Interestingly, the Ugandan giraffe made up for some of its short stature with a neck length that was actually slightly longer than that of a subadult giraffe at almost 1.5 meters (4.9 feet) compared to the normal 1.4 (4.6 feet). In this department the Namibian giraffe was once again below average.
The authors write that this is the first time this kind of skeletal dysplasia has been reported in wild giraffes, and having spoken to some members of the zoo community it doesn’t appear to have been witnessed in any captive animals either. How common it is in nature is hard to deduce from photographic surveys as finding such animals is a bit like looking for a short fluffy needle in a stack of slightly taller fluffy needles. That the researchers have been unable to find any members of the scientific and zoo communities who have seen this in giraffes before does however indicate that it is probably quite rare.
So why did these two animals not grow the long legs that are characteristic of giraffes? “It’s difficult to say for certain, but we speculate that these skeletal dysplasias may be associated with some genetic disorder, as the emergence of skeletal dysplasias are often rooted in molecular etiologies,” co-author Michael B Brown, a conservation biologist with the Giraffe Conservation Foundation, told IFLScience.
“It’s worth noting that the Murchison Falls National Park giraffe population in Uganda experienced a significant population bottleneck in the late 1980s as a result of civil unrest and poaching. The population has rebounded remarkably since then with current estimates of over 1,500 giraffe, although it’s unclear if there are any lingering impacts of the earlier population bottleneck.”