The effect of fire on habitat selection of mammalian herbivores: the role of body size and vegetation characteristics.

Given the role of fire in shaping ecosystems, especially grasslands and savannas, it is important to understand its broader impact on these systems. Post-fire stimulation of plant nutrients is thought to benefit grazing mammals and explain their preference for burned areas. However, fire also reduces vegetation height and increases visibility, thereby potentially reducing predation risk. Consequently, fire may be more beneficial to smaller herbivores, with higher nutritional needs and greater risks of predation. We tested the impacts of burning on different sized herbivores' habitat preference in Serengeti National Park, as mediated by burning's effects on vegetation height, live : dead biomass ratio and leaf nutrients. Burning caused a less than 4 month increase in leaf nitrogen (N), and leaf non-N nutrients [copper (Cu), potassium (K), and magnesium (Mg)] and a decrease in vegetation height and live : dead biomass. During this period, total herbivore counts were higher on burned areas. Generally, smaller herbivores preferred burned areas more strongly than larger herbivores. Unfortunately, it was not possible to determine the vegetation characteristics that explained burned area preference for each of the herbivore species observed. However, total herbivore abundance and impala (Aepyceros melampus) preference for burned areas was due to the increases in non-N nutrients caused by burning. These findings suggest that burned area attractiveness to herbivores is mainly driven by changes to forage quality and not potential decreases in predation risk caused by reductions in vegetation height.