BATS
Microbats are predominantly insectivores except for the largest native microbat, the ghost bat (Macroderma gigas), which is a generalist carnivore (Table 14.4). Insectivorous bats have a relatively simple glandular stomach, except for the pyloric region (Fig.
14.3). The simple small intestine and colon are internally distinguished by a change in vil- liform to longitudinal folds respectively (Stevens and Hume 1995). The dentition, digestive physiology, and diet of Pteropodidae (flying foxes) are covered in Olsson and Woods (2008).Insectivorous bats can benefit from the digesta present in the insects they consume. Symbiotic gut bacteria may help to assimilate chitin from the exoskeleton of prey (Whitaker et al. 2004). The microbiome of most adult bats is dominated by Gammaproteobacteria but the microbiome does change with diet. Insectivorous bats harbour high populations of Planctomycetes and Del- taproteobacteria and frugivorous bats have populations of Tenericutes and Firmicutes (Carrillo-Araujo et al.
2015). Captive management of insectivores relies on adequate gut-loading diets of insects to provide optimal nutrition to the animal. Wombaroo® Insectivore Mix and Wombaroo Insect Booster are common supplements added to the diet of mealworms fed to insectivorous bats, supplementing levels of calcium and vitamins (A, D, E, and B-complex) that would otherwise be deficient on an insect-only diet. Analysis of gut-loaded insects is recommended to ensure nutrient levels are being achieved. Metabolic bone disease is seen in hand-raised pups or juveniles fed on milk formulas without acceptable vitamin D and calcium levels (Lollar 2010). An absence of a healthy microbiome in hand-raised pups commonly results in bloat. Transfaunation or the addition of a suitable probiotic to milk formula may encourage beneficial gut flora to establish.
Herbivorous flying-foxes (Pteropus spp.) feed on nectar, pollen and fruits, where larger species (e.g. the grey-headed flying-fox P. policephalus) typically have a fruit-dominated diet which includes nectar and smaller flying-foxes (e.g. the little red flying-fox P. scapulatus) have a nectar dominated diet supplemented with fruits (Bradford et al. 2022). Faecal DNA evidence shows that grey-headed flying-foxes supplement their diet with insects such as cicadas (Smith et al. 2020), and a small portion of invertebrate prey and a protein supplement in the managed care diet may be suitable.
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