Although smaller bats are consumed by "N. grandis", they are only eaten when they fly into the roosts of "N. grandis". "N. grandis" produces low-intensity echolocation calls at high frequencies, which makes them nearly inaudible except at close range. Instead of relying on echolocation to find their prey, these bats listen for wing fluttering of smaller bats and even insects. However, as "N. grandis" gets closer to its prey during a hunt, it exudes a louder echolocation call. At the beginning of the pursuit, the call ranges from 17–114 kHz, and rises to a range of 61–110 kHz just before the prey is caught. This bat resides uniformly across Eastern, Central, and Western Africa. It tends to be limited to savannah woodlands and rainforests, especially the coastal forests of East Africa. They use hollowed out trees or rocky caverns as roosting locations. Some examples of trees in which "N. grandis" tends to roost are "Acacia aldiba, Adansonia digitata", and "Mitragyna stipulosa". When living in captivity, these bats roost in artificial structures such as houses, culverts, and water towers. Though this bat is an opportunistic predator (diet depends upon prey availability), smaller bats, fish, and frogs constitute much of the biomass of its diet, so changes in rainfall such as drought can be detrimental to them by eliminating larger prey. As this species is strong, it preys on other bats, birds, scorpions, sun spiders, frogs, and even grabs fish near the surface of the water. It swoops onto its prey. The bats that it consumes tend to weigh 5-10 g. "N. grandis" will consume smaller bats during the winter season (June and July), and will only eat smaller bats that have entered the roost during the remainder of the year. Bats, frogs, and fish are important as prey because they constitute most of the biomass of "N. grandis"' diet, whereas arthropods make up less than 20% of the diet. As mentioned, these bats are opportunistic predators, so geographical variation and changes in rainfall have a tremendous impact on their diet. "N. grandis" uses rate of encounter with prey to determine which foraging style would be the most advantageous, and uses this information to adjust its prey selection.