Little brown bats mate in two different ways. Mating occurs right before hibernation in the hibernaculum roost. Sometimes both the male and female are awake and alert when mating takes place. But sometimes, males mate with other bats who have already entered hibernation. Mating is random and both males and female mate with more than one other bat.
Mating System: polygynandrous (promiscuous)
Little brown bats hibernate in a special roost called a hibernaculum. When the temperature falls during late summer and autumn, bats begin swarming at the hibernaculum. Swarming helps young bats find suitable hibernation roosts. The first bats to arrive at the hibernaculum in late July are adult males, and females without young. Females and subadults arrive in August.
Even though little brown bats mate in autumn, females delay ovulation and store sperm for about seven months before they actually get pregnant in spring. Pregnancy lasts 50 to 60 days. Pups are born in June and July. Females give birth to only one pup each year.
Normally, bats hang with their heads pointed down. When females give birth, they reverse their position so the head is up. Mothers catch their newborn young in a special membrane between their legs. A pup is born with a full set of teeth. Its eyes and ears open within hours of birth. A pup clings to to its mother's nipple using its teeth, thumbs, and hind feet.
When the bat pups are 9.5 days old, they can control the temperature of their bodies. They can hear as well as adults by the time they are 13 days old. Young can fly by the time they are 3 weeks old. Pups become independent and self-supporting about 4 weeks after they are born. By this time they are as big as adults.
Breeding interval: Both sexes mate more than once per year and produce one young per year.
Breeding season: Mating begins in mid-August during the active phase and continues in passive phase throughout the winter.
Range number of offspring: 1 to 2.
Average number of offspring: 1.
Range gestation period: 50 to 60 days.
Range weaning age: 21 to 28 days.
Average weaning age: 26 days.
Average time to independence: 4 weeks.
Average age at sexual or reproductive maturity (female): 210 days.
Average age at sexual or reproductive maturity (male): 210 days.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous ; sperm-storing ; delayed fertilization
Average birth mass: 1.96 g.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 210 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 210 days.
Mother little brown bats provide all of the parental care. A mother can identify her own pup by its odor and its calls.
The mother provides milk to her young, and for 18 to 21 days this is all the pup eats. At about 3 weeks of age, the permanent teeth of a pup come in, allowing it to feed on insects along with the mother's milk.
Weaned pups lose weight when they are first learning to catch insects. Scientists are not sure if mothers bring insects to their young or actively teach them to hunt. However, because mothers and their young stay together, scientists believe that the young are learning from their mother before they become independent.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female)