Pteropus
Reproduction and life cycle

Many species of flying fox are polygynandrous, meaning that each individual will mate with several other individuals. The Samoa flying fox is a notable exception because it is monogamous. Flying fox sexual behaviors include oral sex in addition to intercourse, with fellatio and cunnilingus observed between opposite sexes, as well as homosexual fellatio in at least one species, the Bonin flying fox. Opposite-sex oral sex is associated with increased duration of intercourse, while same-sex fellatio is hypothesized to encourage colony formation of otherwise-antagonistic males in colder climates.

Flying fox gestation length varies among species; gestation length is 140 – 190 days (4.6 – 6.3 months).Females have a litter size of one young at a time, called a pup. Twins have been occasionally documented in some species, however. Twins can be fraternal, identical, or the result of superfetation. Pups are altricial and sparsely furred at birth, thereby dependent on their mothers for care. Pups are relatively small at birth, weighing approximately 12% of the mother's weight. Bats in other genera can have pups that weigh as much as 30% of the mother's weight at birth. They cling to their mothers' abdomens, gripping her fur with their thumb claws and teeth; females carry the pups for the first several weeks of life. After this, the females may leave the pups behind at the roost at night while they forage. As with nearly all bat species, males do not assist females in parental care. While male flying foxes of at least one species, the Bismarck masked flying fox, can lactate, it is unclear if the lactation is functional and males actually nurse pups or if it is a result of stress or malnutrition. Pups fledge beginning at 3 months old, but may not be weaned until 4 – 6 months old. Pups may stay with their mothers until age one. Flying foxes do not reach sexual maturity until 1.5 – 2 years old. Females can have up to two litters annually, though one is the norm due to the long weaning period. Most flying foxes are seasonal breeders and give birth in the spring, though the Mariana fruit bat seems to have aseasonal breeding with new pups documented throughout the year. Females remain fertile with no decrease in reproductive capability for at least the first 12 or 13 years of life.

Flying foxes, like all bats, are long-lived relative to their size. In the wild, average lifespans are likely 15 years. However, individuals part of populations that face excessive disturbance may have lifespans as short as 7.1 years. In captivity, individuals can live approximately 20 – 28 years. The longest-lived flying fox was an Indian flying fox named Statler, who was a resident at Bat World Sanctuary for his last few years. He was born at a zoo in 1987, and was 34 years old at the time of his death.
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