How do we know what bats eat?
There are lots of ways to work out what a bat eats. sometimes, if we are very lucky, we see the bat feeding directly, or catch it at a feeding site like a fruiting tree. A mist net set at a flowering durian tree will usually catch the lesser dawn bat (Eonycteris spelaea) coming to feed on the nectar and pollinate the flowers, and we catch its smaller cousin, the greater long-tongued bat (Macroglossus sobrinus) with nets by banana flowers. *** photos***
But this only gives a small part of the diet — Eonycteris can’t rely on durian flowers alone as they don’t flower all year. To work out what else they eat, we often end up looking at feces or the rejecta pellets of plant matter that the bat hasn’t swallowed but spat out. There are often seed and fragments of the fruit in both feces and rejecta pellets and it is sometimes possible to match them to fruits in the forest or garden. If we are really stumped, we may even try to germinate the seeds from the bats and identify the plants when they are seedlings or young plants.
Working out what insectivorous bats eat is rather similar — we look at the fragments of insect parts in the feces and try and match them with insects caught in the area where the bat forages. Some insectivorous bats use a special roost at night just for feeding and will drop the inedible parts of their prey (the insect wings and wing cases) to the ground below. We can often identify the insects form these remains, and this enables us to build up a picture of the diet.
