Impact of bush fire on grazing behaviour of herbivores in Masai Mara

Abstract: Fire is commonly used in African savannas to remove long, dry, low-nutritious grass and generate fresh grass, both for livestock and wildlife. Since different herbivore species have different demands on amount and quality of biomass, bush fires might change the composition of the herbivore community. I studied how grass fires on the savannah affected habitat choice and foraging behaviour of the animals in the Masai Mara Conservancy in south-western Kenya. In August and September 2005 I observed several species of animals on burnt and non-burnt areas. Along a set of transects we recorded abundance and behaviour on burnt and non-burnt areas. Each of the 54 transects was 1000 m long and 300 m wide, thus covering an area of 0.3 km2. The study was carried out during August and September 2005, after fires in June and October 2004 and July 2005. We placed 18 transects on areas burnt one month ago, 18 were burnt in the previous year, and 18 were controls which had not been burnt for at least two years. Recently burnt areas provided less biomass but of higher energy and protein content with less fibre than controls and areas burnt during the previous year. All observations were made between 6.30 am and 18.30 pm. This range of time was divided into 12 one-hour periods, and during the study each transect was driven once in each one-hour period. From 35 observed species I present data from the most frequent species; blue wildebeest (Connochaetes taurinus), Burchell's zebra (Equus burchelli), Thomson's gazelle (Gazella thomsonii), warthog (Phacochoerus africanus), African elephant (Loxodonta africana), buffalo (Syncerus caffer), and topi (Damaliscus lunatus) were more thoroughly examined. Wildebeest, Thomson's gazelle and warthog were all found in larger numbers the burnt areas. There were more zebras on burnt areas but I failed to show a statistical significance. Zebra and Thomson were on areas with shortest grass of highest quality and wildebeest on medium-high grass. Buffalo and elephant were predominantly found on tall grass. Although the elephants were only observed on tall grass, the observations were too few to generate a significant difference. There was no significant difference in the numbers of topis on the burnt and non-burnt areas, respectively. Differences between species can be explained in part by the anatomy and physiology of their digestive systems, and could also be affected by the increased visibility of predators in the shorter vegetation on the burnt areas. With these data we gain knowledge on how fires can be used to influence vegetation and abundance of herbivore