The ecological impacts of a migratory bat aggregation on its seasonal roost in Kasanka National Park, Zambia

The ecological impacts of migratory species on their seasonal environments are poorly known. The effects of several million straw-coloured fruit bats (Eidolon helvum), which migrate seasonally to Kasanka National Park, Zambia each year, on the small area of mushitu'swamp' forest in which they roost, were investigated. The structure of the mushitu forest was profoundly altered by the presence of E. helvum, with increased roost tree mortality, lowering and opening of the forest canopy and a decrease in tree basal area. Eidolon helvum are also thought to increase the severity of fires within their roost site because the structural changes result in a drier microclimate. The effects of increased nitrogen and phosphorous input were less apparent. These findings suggest that the ecological impact of this migratory bat species on its seasonal environment could ultimately threaten the long-term viability of its seasonal roost.