Diadem roundleaf bats are predominantly insectivorous, feeding mostly on large insects, favouring beetles, grasshoppers and locusts, and moths (10) (11). This species is also carnivorous having been recorded feeding on birds at two sites in Australia (10). The main foraging method is perch hunting which is a low-energy strategy. Its prey commonly move with direct and predictable flight paths, making it possible for the bats to hang from a tree branch, up to ten metres above the ground, waiting for a suitable insect to fly past. Whilst at the perch, the bat scans the area using echolocation at a constant frequency of 58 to 60 kilohertz. Once it has detected an insect, it drops from its perch and flies fast and straight to snatch its quarry from the air.
The size of the pup relative to the mother in insectivorous bats is remarkable. This species can give birth to a single pup weighing 13 grams – a quarter of its mother’s weight. The mother must carry the pup on foraging trips until it is developed enough to fly and feed alone. By one year the young diadem roundleaf bat will be ready to breed (3).