Secrets Behind the Stripes

There are many ungulate species in Kruger National Park. Ungulate species are animals that are hoofed. One of the odd-toed ungulates seen throughout Kruger is the Burchell’s zebra. There are two different subspecies of zebra, the Burchell’s zebra pictured above, and the Hartmann’s zebra which can be found in central and south Namibia. Zebras all have unique stripe patterns - no two zebras have the same patterns. Similar to humans having melanism zebras can have more black pigment, which is called melanistic colorization. These zebra’s coloration can vary from excessively large stripes to a nearly complete black appearance. If an almost completely black zebra is seen, one could infer it is due to the melanistic trait. This type of coloration is rare in large populations. As observed by a study conducted by Caputo et al., it was hypothesized that the melanistic coloration effects the animal’s fitness based on social interactions (Caputo et al.,2017). In the study, they observed two different melanistic zebras in the Eastern Cape Province of South Africa. They would take photographs of the animals and observe how many other zebras were within 100m of the melanistic zebra. They also quantified the amount of black to white by visually estimating the black to the white ratio on different sections of the animal. Where there was striping, the number of stripes was counted, and the shape of the stripes was described. Throughout the observations, it was noticed that both of the observed zebras were welcomed by other members of their herd. Both zebra A and B were observed grazing in close proximity to other zebras. According to Kingdon (1984), zebra with unusual coating patterns would not benefit from social interactions and would likely suffer a reduction in fitness. Distortions of typical coloration and/or patterning may result in an inability to attract mates, engage in social behaviors or inactive rejection by conspecifics (Kingdon,1984). However, given the behavior witnessed from zebra A and B, one could conclude there are no signs of social rejection due to the melanistic colorization. But because there was no obvious rejection, there will need to be further research done with longer observation periods to determine if the more subtle rejection is occurring and to investigate the mechanisms of mate selection for this species (Caputo et al., 2017). Because stripes are harder for predators to see (Melin et al., 2016) this suggests that melanistic zebras would not have a high risk of predation due to lack of stripes, but rather the lack of stripes is a sign of weakness or genetic defects. But because there is a lack of predators in the area in which these animals were observed this could not be evaluated at the time (Caputo et al., 2017).

Work Cited

Caputo, M., Rubenstein, D. I., Froneman, P. W., & Bouveroux, T. (2017).

Striping patterns may not influence social interactions and mating in zebra: Observations from melanic zebra in South Africa. African Journal of Ecology,56(2), 428–431. doi:10.1111/aje.12463