the day. Caracal, serval, honey badger and the rare Meller's mongoose occur but are very seldom sighted. Two species of otter live in Kasanka’s rivers, marshes and lakes. Bats The first of Kasanka’s famous straw-coloured fruit bats (Eidolon helvum) start arriving towards the middle of October each year. By mid-November the roost has reached its highest density and numbers are estimated to be around eight to ten million. It is believed to be the highest density of mammalian biomass on the planet, as well as the greatest known mammal migration. The arrival of the bats normally coincides with the start of the first rains and the ripening of many local fruit and berry species such as the masuku (wild loquat) and waterberry, on which the bats feed. It is estimated that 330,000 tonnes of fruits are consumed by the bats during the three months. The bat roost is centred on one of the largest remaining patches of Mushitu (indigenous forest) in Kasanka along the Musola stream. There are a number of excellent 'hides' in trees at the edge of the forest which provide fantastic sightings of the bats in flight at dawn and dusk. The high concentration of bats attracts an incredible variety of predators and scavengers to the bat forest. Martial eagles, pythons, fish eagles, lesser-spotted and African hawk-eagles, kites, vultures and hobby falcons are amongst the raptors that concentrate on the roost for easy pickings, whereas leopard, water monitors and crocodiles make off with those bats unfortunate enough to drop to the forest floor. The origin of the various colonies that make up this 'mega-colony' has never been fully established, however it is known that bats travel from other parts of Africa including Congo. Studies indicate that the abundance of fruits during the season are the major reason for the migration. The bats' arrival starts gradually during the first week of October, numbers peak in November and early December. Numbers start to decrease around the second week of December. The departure of the last bats has been getting later over recent years, with the final bats now generally leaving Kasanka in early January. A study published in the African Journal of Ecology indicated that the migratory impact of the bats could ultimately threaten the viability of the seasonal roost as it increases faster tree mortality. The Kasanka Trust undertakes an extensive fire management program to protect the forest