only swallowing smaller seeds of the meal. Incisors hold items such as fruit, and the fibrous material is ejected from the mouth after it is masticated and the juice is swallowed; larger seeds may be held in the mouth and dispersed several kilometres from the tree. The need for the elaborate intestinal tract of most herbivores is consequently removed. Some fruiting plants produce food for flying-foxes, and P. poliocephalus is attracted to the scent of their flowers and fruit and is able to locate the pale colour that indicates the source; the fruit and blooms of species that attract birds in the daylight are usually contrasting reds and purples. The food source is also presented away from the foliage that may obstruct the bat's access. Most of the trees on which this species forages produce nectar and pollen seasonally and are abundant unpredictably, so the flying fox's migration traits cope with this. The time when flying foxes leave their roosts to feed depends on foraging light and predation risk. Flying foxes have more time and light when foraging if they leave their roosts early in the day. The entire colony may leave later if a predatory bird is present, while lactating females leave earlier. With males, the bachelors leave earlier than harem-holding males, which guard and wait until all their females have left. The flying foxes that leave the roost earlier are more vulnerable to predation, and some flying foxes will wait for others to leave, a phenomenon labelled the "after you" effect. Social organisation Groupings and territories Grey-headed flying foxes form two different roosting camps, summer camps and winter camps. Summer camps are used from September to April or June. In these camps, they establish territories, mate, and reproduce. Winter camps are used from April to September. The sexes are separated in winter camps and most behaviour is characterised by mutual grooming. Summer camps are considered "main camps", while winter camps are referred to as "transit camps". In their summer camps, starting in January, male grey-headed flying foxes set up mating territories. Mating territories are generally 3.5 body lengths along branches. These flying foxes' neck glands enlarge in males in the mating season, and are used to mark the territories. The males fight to maintain their territories, and this is associated with a steep drop in the males' body condition during this time. Around the beginning of the mating