Mechanism

Fruit bats consume leaves by practicing mastication, or leaf fractionation. This involves chewing the leaves and swallowing the liquid while expelling the leftover fibrous tissue. The leftover fibrous tissue forms pellets on the ground, which is how researches tell that fruit bats are ingesting leaves (2).   


A partially eaten leaf and the rejected leaf pellets found in a cave where fruit bats roost are shown in the image to the right (1).

The digestive system in fruit bats are designed to only handle small amounts of food, but the practice of only swallowing the liquid from plants enables them to obtain nutrients from plants without increasing the size of their digestive tract (1).

 


A fruit bat eating a piece of fruit shown above (20).

As you can see, megachiroptera generally have large eyes and noses, which enable them to find certain fruit and leaves, and this may be why folivory is more common in megachiroptera than microchiroptera, which have smaller eyes and rely mainly on echolocation to locate their food. Their excellent senses of smell and sight make their diet of fruit and plants advantageous(8).

Folivory in fruit bats has only been observed for short periods, but recently researchers Damian Ruiz-Ramoni and his colleagues have found leaf pellets year round in bat caves, suggesting that folivory isn't a seasonal phenomenon (6). 

The physiological mechanisms for folivory are yet to be found since this behavior is relatively newly discovered. Some questions that might be answered in the future include: 

What are the external and internal cues that trigger folivory? 
What processes in the brain occur during folivory? 
Do hormones play a role in stimulating this behavior?