The diet of Hipposideros diadema was investigated over three seasons at two sites on Cape York Peninsula, Australia using faecal analysis (at both sites) and prey remains identification (at one site). The possibility that this species feeds on terrestrial vertebrates, a behaviour here referred to as carnivory, was suggested by the similarity of three of its morphological features with those of eight of the 10 species of bats known to exhibit carnivory.
The study confirmed that H. diadema is at least occasionally carnivorous. Bird feathers were found in faeces at both sites; however, their occurrence was limited to a collection of faecal pellets from the early dry season at Iron Range and a single pellet from the wet season at Chillagoe. The birds taken could not be identified to family or species. Coleoptera, Lepidoptera and various orthopteroid orders were the main insect taxa in faecal pellets. The frequency of these taxa in the diet varied significantly among the three seasons at both sites. Analysis of prey remains indicated that large, hard-bodied insects, mainly cerambycid and scarabaeid beetles and acridid grasshoppers, particularly the locust Gastrimargus musicus, were taken frequently. The mean length of intact beetle elytra collected below roosts was 18.0 mm. No vertebrate material was found in prey remains. Hipposideros diadema is similar to several other bats which exhibit carnivory in preying infrequently on vertebrates. The term ‘partial carnivore’ or ‘occasional carnivore’ is suggested for these species.