Department of Physics, Chemistry and Biology (IFM)

Different species of herbivores often share the same type of savanna. Normally they use different plants or different parts of the same plant ¹. Decrease in grazing and browsing can lead to an increase in biomass which can result in extensive fires ², but if grazing pressure is too high it can prevent fire outbreaks ³. Burnt and un-burnt areas form a mosaic pattern in the landscape which provides a varying quality of food ⁵ and therefore attract different species of herbivores ⁴. The re-grown grass following a fire has a high nutritional value but the quantity is relatively low ⁶. Burchell’s zebra (Equus burchelli) is classified as a bulk and roughage feeder ⁷ but is often observed to graze on newly burnt areas ⁶.

To see which types of savanna Burchell’s zebra prefer, we used areas that were burnt in June (E) and in October (L). Areas that had not been burnt for several years served as controls (C). We selected 36 transects, 9 transects in E, 9 in L and 18 in C. Transects were 1.0 km long and truncated 150 m on both sides. We cut 20 grass samples per transect to record fresh and dry matter. Transects were driven once per hour 6:30 -18:30, i.e. 12 times per observation period. Observers were sitting on seats on the roof of a slowly driving off-road car.

The habitat use was higher both at early fire (P = 0.005) and late fire (P < 0.001) compared to control areas. Late fire areas showed a higher use (P = 0.031) than early fire (Figure 1). There was a significant negative correlation (R = -0.629, P < 0.001) between the number of Burchell’s zebra per hectare and the grass biomass per hectare.

Late fire areas were the most preferred habitat followed by early fire areas. Controls showed the lowest preference. Animals choose the most suitable area according to their need of quality and quantity of food, risk of predation and their own morphology.

Burchell’s zebra possess powerful incisors that easily can cut fibrous stems compared to wildebeest (Connochaetes taurinus) which upper incisors are absent and the lower close against the hard palate. This cutting mechanism is effective for long grass while the mechanism in Burchell’s zebra is effective for cutting shorter grass ⁸.

According to Duncan et al. ⁹, food requirement in ruminants and in non-ruminants differ due to differences in their gut morphology. Non ruminants normally have a higher rate of food intake and the digestibility of plant material is higher than in ruminants. Horses in general and Burchell’s zebra compensate this partly through a very large cecum with bacterial activity. The cecum is used as a fermentation chamber instead of the rumen ¹⁰. According to Bell ¹¹, the protein extraction in non-ruminants is not as effective as in ruminants. To maintain the same absorption rate, the strategy is to increase the rate of intake and reduce the passage time.

Ben-Shahar & Coe ¹² showed that food intake of Burchell’s zebra was correlated with the levels of N and P in the grasses. Sing et al. ¹³ found that the level of N and P generally was higher in savannas that were recently burnt compared to non-burnt savanna. Gureja & Owen-Smith ⁶ showed that Burchell’s zebra prefer grass less than 100 mm in length and may also migrate to find areas with suitable length. In a study where wildebeest and Burchell’s zebra were compared with focus on their intake of crude protein, Bodenstein et al. ¹⁴ found that Burchell’s zebra preferred a higher concentration of crude protein compared to wildebeest. One of our late fire transects did not burn efficiently which resulted in a higher amount of biomass after the fire compared to other late fire transects nearby. On this transect wildebeest was much more abundant than in any other late fire transect whilst late fire transects nearby instead had a higher abundance by Burchell’s zebra. Due to the properties of this transect, it was more comparable to early fire areas. This agrees with the present study. The classification of Burchell’s zebra as a bulk roughage feeder does not agree with our findings.

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