At dusk, flying-foxes leave their roosts in search of food and return just before dawn the next morning. They fly out in several streams in various directions to go to different feeding sites. Many flying-foxes will feed in the same tree (V. Jones, 2008, personal communication), however they maintain feeding territories through vocalizations (Nelson, 1965). The grey-headed flying fox’s diet consists mainly of nectar (V. Jones, 2008, personal communication) but also of fruit, flowers, and pollen from over 187 different plant species (Williams et al., 2006). Flying-foxes are “sequential specialists,” meaning that they feed on a variety of foods but according to preference (Parry-Jones & Augee, 2001).

While eating, flying-foxes extract nectar and juice from their food by crushing it against the roofs of their mouths, and then spit out the remaining part of the food.  This allows them to minimize their weight in order to enhance their flying ability.  To keep remain hydrated, flying-foxes lick water caught on leaves in trees as well as water on their stomachs from skimming the surface of a water source (V. Jones, 2008, personal communication). 

Urbanization, as discussed in the social spacing section, has drastically changed the habitat of the grey-headed flying-fox, and has made it necessary to understand their behaviors within the new urban environment.  McDonald-Madden et al. (2005) examined the factors affecting foraging site choice for the flying-foxes in the Melbourne Botanical Gardens colony of about 21,000 individuals.  Six factors were investigated including the distance of the food source site from the colony, the distance of the food source site from the Yarra River, the tree density of the colony, whether the food source site was a park or street, the tree density of the food source site, and whether individuals found food at the food source site (McDonald-Madden et al., 2005).

McDonald-Madden et al. (2005) explain that the flying-fox decision to use various food source sites is a balancing act between the costs and the benefits of that site.  Various costs and benefits include those factors listed above.  For example, the closer the food site is to the colony, the less energy the individual has to use to get to its food.  Also, the greater the tree density of the food source site, the greater protection from predators while foraging (McDonald-Madden, 2005).

McDonald-Madden et al., (2005) found that four of the factors were significant predictors of whether a food site was used or not.  As the distance of the food source site from the colony increases, the probability of the flying-foxes foraging there decreases.  As the tree cover of the food source site increases, the probability of the flying-fox foraging there increases.  Food sources in parks as opposed to streets and sites where food is generally present were preferred (McDonald-Madden, 2005).

            The emergence time of a flying-fox from its roost is a result of a cost-benefit relationship between foraging light and predation risk.  The earlier the emergence, the more time and light a flying-fox will have in foraging for food (Welbergen, 2006).  Flying-foxes travel great distances of more than 60 km to find food in one night, therefore maximization of foraging time not only gives an individual preferential access to the best food resources but also maximizes feeding time (V. Jones, 2008, personal communication).  Also, adult females emerge earlier than males due to their greater need for nutrition while pregnant, nursing, or caring for young, which they carry while foraging (Welbergen, 2006).

However, with an earlier emergence time also comes increased predation risk by avian predators such as white-bellied sea eagles and wedge-tailed eagles.  In general, Welbergen (2006) found that emergence times were delayed when an avian predator was present.  This occurs because of the selfish herd concept.  The individuals who leave first are more susceptible to predation, which is called marginal predation.  Therefore a flying-fox will wait for others to leave first, a phenomenon Welbergen calls the “after you effect.”  Also, younger flying-foxes leave the colony later than older individuals because they are more susceptible to predation (Welbergen, 2006).