Digestive Anatomy and Physiology

The Indian flying fox and the grey-headed flying fox have very similar diets. They are both frugivores that use figs as a major component of their diet. Both species also consume flowers, leaves and seeds.[4,7,11,20,25] They are also closely related and are large fruit bats. Therefore, it is reasonable to assume that they share a similar digestive tract.

There is no diagram available of the gastrointestinal tract of either the Indian flying fox or the grey-headed flying fox. The following diagram is a depiction of the GI tract of Artibeus jameicensis, the Jamaican fruit bat. The Jamaican fruit bat is a larger frugivore that has a similarly diverse diet; figs also make up a significant portion of its diet.[19] Therefore, it is likely that the GI tract of the Jamaican fruit bat resembles the GI tract of the Indian and grey-headed flying fox.

The GIT of the Jamaican fruit bat, Artibeus jameicensis[19]

The digestive system of these two bats has not been studied in detail. However, grey-headed flying foxes have been observed consuming insects, so it is likely that their digestive system follows that of an omnivore.[4] Alternatively, their digestive system may more closely resemble that of a foregut fermenter with only a forestomach; they do not have a caecum and do not practice coprophagy, so they are not hindgut fermenters.[24] Therefore, based off of this information, we can assume that the digestive system of the Indian and grey-headed flying fox follows that of either an omnivore or a forestomach foregut fermenter. With this in mind, the progression of their digestive system is likely as follows[22]:

  • Mouth
  • Esophagus
  • Forestomach (possibly)
  • Stomach/abomasum
  • Small intestine (duodenum, jejunum, ileum)
  • Large intestine
  • Rectum
  • Anus

Some modifications to the typical mammalian digestive system include:

  • As mentioned, the grey-headed flying fox does not have a caecum.[24] There is no information on the presence or absence of a caecum in the Indian flying fox.
  • Bats tend to have shorter intestinal length than mammals of similar size.[3,15]
    • This is likely a strategy to allow them to stay lighter, making flying more energy efficient.[3,15,24]
    • Bats may have an enhanced paracellular pathway for absorption of glucose and amino acids.[3]
    • The surface area of villi relative to non-villi area in the intestine is greater in bats than terrestrial mammals by at least 59%.[3]
    • The typical fruit bat feeding strategy of sucking the juice from plants allows them to extract carbohydrate-heavy juice; carbohydrates are easily digested, even with a short transit time.[15] This strategy means that they lose some of the potential energy found within the fruit, but it allows them to eat many fruits quickly.
  • The Indian flying fox has specialized bacteria in the intestines to help digest cellulose and xylan into glucose, which can be absorbed in the intestine.[21] Because of this, leaves are an important part of their diet.[21]