The social spacing of flying-foxes includes a home range with several roosting camps in which males maintain mating-only territories, or leks, described in further detail in the mating system section.  It has also be reported that flying-foxes have feeding territories outside of the roosting camp that they guard through vocalization (Nelson, 1965). 

Flying-foxes have large home ranges of which some individuals utilize small portions; however the majority uses almost the entire range (V. Jones, 2008, personal communication). They live in various social groups and locations depending on the time of year and the stage in the reproductive cycle. Factors affecting camp site choice include availability of food resources and the reproductive cycle of the flying-fox.  Tidemann et al. (1999) found that flying-fox camps had available forage within 20 km and that the camps were found in riparian vegetation, or in other words next to a water source. Despite these specific characteristics, flying-fox camps can appear in many different environments and are not dependent on any one factor (V. Jones, 2008 personal communication). Other factors affecting camp site choice include hunting by humans, natural disasters, and climate fluctuations (Tidemann et al., 1999). 

Based on changes in food resource availability and reproduction needs, flying-foxes form two types of camps, summer and winter camps (Nelson, 1965), that can contain hundreds of thousands of individuals (Welbergen, n.d.).  Summer camps are used from September to April or June and are often used each year during those months.  It is in these summer camps that flying-foxes establish territories, select their mates, and  reproduce (Nelson, 1965).  Often these camps are referred to as main camps and have populations of greater than 1,000 individuals (Vardon et al., 2001). This increase in camp population in the summer is more pronounced in the southern portion of their range and may not be the case farther north (V. Jones, 2008, personal communication).

Winter camps are used from April or June to September and are used for only a few years before they are replaced by another location. Unlike the summer camps, winter camps are often sexually segregated and very little aggressive behavior is present with mutual grooming occurring frequently (Nelson, 1965).  These camps are those to which the flying-foxes migrate from the main camps and can be referred to as transit camps (Tidemann & Nelson, 2004) or satellite camps (Vardon et al., 2001).

Regardless of season, however, the main driving factor in flying-fox movement is food resource availability (V. Jones, 2008, personal communication).  Vardon et al. (2001) note that the first migratory shift from the satellite camps to the main camps occurs after the rainy season when food availability is low, and that the second shift moves the population from the main camps back to the satellite camps and occurs after individuals mate. In addition to seasonal changes in food availability, flying-fox migration is dependent on the irregular blossoming patterns of several plant species in their home ranges.  If a food resource becomes scarce in one area flying-foxes will migrate to other areas in which food is plentiful.  For that reason, it may be difficult to classify camps as “main” or “transit” because flying-fox populations are very fluid.  Some camps are used very frequently and others infrequently.  For example, some female flying-foxes will shift camps very often and some males may stay in the same camp yearround (V. Jones, 2008, personal communication). Other potential factors affecting the migration of flying-foxes to and from various camps include mating opportunities and information gathering (Tidemann & Nelson, 2004). 

Photo Courtesy of Vivien Jones

There are many advantages of living in a large colony like those of the grey-headed flying-fox.  Large camps of flying-foxes provide excellent predator protection through increased vigilance and decreased chance of an individual being picked off by a predator due to the larger group size, also known as the selfish herd effect. Large camps also facilitate reproduction by providing increased chances of finding a mate and protection for the young (Nelson, 1965; Tidemann et al., 1999). Even other species of flying-foxes, Pteropus scapulatus and P. gouldi, seek protection by inhabiting and forming separate groups within the colonies of the grey-headed flying-fox (Nelson, 1965).

Other potential advantages include enhanced population spacing, low territory-protection cost, and greater passing on of genes by males (Nelson, 1965).  Information exchange is potentially another advantage of these large groups, however this area has not been heavily researched in relation to the flying-fox (Tidemann et al., 1999).

Urbanization of the eastern coast of Australia has had a significant effect on the flying-fox populations in the area. Even though urbanization results in loss of habitat and reduced population size for many species, the flying-fox has dealt well with its new urban environment. Several flying-fox populations have relocated their camps to urban settings and have undergone behavioral changes as a result (Williams et al., 2006). 

van der Ree et al. (2006) examined the history of the establishment of the flying-fox camp in the Royal Botanic Gardens (RBGM) in Melbourne, Australia.  While the first recorded flying-fox sighting in Melbourne occurred in 1884, it wasn’t until 1986 that flying-foxes established a permanent camp.  At the time, the closest flying-fox colony was 450km away from the RGBM colony.  The RBGM camp contains the key characteristics of flying-fox camp sites including being near a water source and seasonal fluctuation in population levels, with more individuals inhabiting the camp during the summer and fall and fewer individuals in thewinter and spring (van der Ree et al., 2006).

There are several reasons why the flying-fox has done so well in their new urban environments. Williams et al. (2006) examined the flying-fox colony in Melbourne and proposed that the flying-fox has prospered urban environments because of an increase in food availability and quantity the city provides. Throughout the urbanization of the flying-fox habitat, food resources have become increasingly abundant, especially in the Botanical Gardens and other parks in the Melbourne area. In addition, European settlement of Melbourne brought the establishment of several plant species that were not indigenous to the area, and tree planting has continued to increase over time (van der Ree et al., 2006).  Not only do these urban environments provide more food resources, they also provide light sources at night by which the flying-fox can navigate the city in foraging (Williams et al., 2006) and protection from human culling (DSE, 2008). 

Photo by Pam Thomas Courtesy of Lubee Bat Conservatory

The changes in roost location due to urbanization has affected several behaviors of the grey-headed flying-fox including migration patterns.  Parry-Jones and Augee (2001) investigated the factors affecting roost inhabitance of the grey-headed flying-fox camp at the Gordon site in Sydney, Australia.  In their natural environment, flying-foxes usually do not inhabit the same camps year-round, switching from summer to winter camps based on factors such as food availability and reproductive needs as mentioned above.  Parry-Jones and Augee noticed, however, that in urban flying-fox camps, migratory patterns have been modified based on the year-round availability of food around these camps, causing many individuals to remain in the same colony throughout the year or move only for reproductive needs (Parry-Jones & Augee, 2001).

Another behavior that has changed in the urbanized flying-fox is feeding behavior including dietary composition.  Parry-Jones and Augee (2001) analyzed the dietary habits of the flying-foxes at the Gordon site through examination of both fecal and other food droppings. Parry-Jones and Augee found that as the amount of pollen in the droppings increased, the size of the colony decreased, and that as the amount of fruit in the droppings increased, the size of the colony increased.  This pattern is not typical of those studied in more natural flying-fox environments.  Parry-Jones and Augee (2001) also found many exotic plant species that have been introduced in urban areas in the droppings of the flying-foxes, indicating that the flying-foxes are taking advantage of these new species and their year-round availability.