The Gerenuk

Height is a characteristic that is commonly asked about as we grow up. However, not everyone grows to be the height that they originally want to be. I am one of those people. Even though I’m short the only time it really bothers me is when I need to reach for something in a grocery store or something in the top cupboard. In order to get the item I want I have learned that I will need to either climb onto something or find a spatula so I can extend my reach. In north-eastern Africa the gerenuk (Litocranius walleri) will stand on its hind legs in order to reach food.

Gerenuk Standing up
 (Miller, 2005)

The gerenuk has long, slender limbs and an elongated neck which separates it from other gazelles. There are many other herbivores living in the same arid conditions resulting in more competition for food in these areas. To reach higher food sources the gerenuk will stand on its hind legs to reach food that other herbivores are unable to reach. This adaptation also helps them in the arid conditions of Africa (Leuthold, 1978a). By standing on their hind legs they are able to reach food sources that contain more water. Their diet has been found to consist mostly of leaves and the tips of shoots. No herbs or grasses were found in their diet suggesting that they rely more on food sources that are higher up (Leuthold, 1978b).

Even though this adaptation helps the gerenuk reach higher food sources and gives it an advantage over species that can’t reach as high, its legs are fragile. If the gerenuk feels threatened and has to run across uneven ground it is more likely to injure its leg. This can be considered a trade-off between its ability to escape and its ability to continuously get food which affects the cost of survival and costs for future reproduction (Steams, 1989). The costs of not getting enough food most likely outweigh the costs of having fragile legs in gerenuks.

Here’s a video of a gerenuk giving birth and the calf taking its first steps:

References:

Leuthold, W 1978a, ‘On social organization and behavior of the gerenuk Litocranius walleri (Brooke 1878)’, Ethology, vol. 47, no. 2, pp. 194-216, doi:10.1111/j.1439-0310.1978.tb01831.x.

Leuthold, W 1978b, ‘On the ecology of the gerenuk Litocranius walleri’, Journal of Animal Ecology, vol. 47, no. 2, pp. 561-580, doi:10.2307/3801.

Miller, R 2005, Gerenuk standing up, Photo, PBase, <http://www.pbase.com/millerr/image/53997572>

Stearns, SC 1989, ‘Trade-offs in life-history evolution’, Functional Ecology, vol. 3, no. 3, pp. 259-268, doi:10.2307/2389364.