Males in California undergo an increase in testes size during the month of August until September and then regress by mid-October. Males are present in nursery colonies as well as in separate single-sex groups. Breeding takes place in early October and continues sporadically throughout the winter. Bats in captivity mate in October and November, some have been observed mating in January and February. In captivity, mated females ovulate and become pregnant with an increase in ambient temperature. Ambient temperature may effect when wild populations produce young, especially if the seasonal temperatures are changing from year to year.
Mating System: polygynandrous (promiscuous)
Females can retain the sperm in the uterus throughout the winter until spring when fertilization occurs. The gestation period lasts from 53 to 71 days and young are born between May and June. They usually have twins, but about 20 percent of births are single. Birth weight is near 3 grams. The young open their eyes about five days after their birth and begin to fly at 4 to 5 weeks after birth. At 6 to 8 weeks after birth they are weaned and are able to breed in their first year.
Breeding interval: Breeding occurs once yearly.
Breeding season: Pallid bats breed beginning in October and throughout the winter.
Range number of offspring: 1 to 3.
Range gestation period: 53 to 71 days.
Average birth mass: 3 g.
Range weaning age: 6 to 8 weeks.
Average time to independence: 1 years.
Average age at sexual or reproductive maturity (female): 1 years.
Average age at sexual or reproductive maturity (male): 1 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); viviparous ; sperm-storing ; delayed fertilization
Average birth mass: 3.1 g.
Average number of offspring: 2.
Average age at sexual or reproductive maturity (male)
Sex: male: 365 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 365 days.
The young are born in an altricial state. They have closed eyes and their ears are folded against the head with a few hairs visible only under magnification. The mothers will carry the young during her foraging flights for the first few days after birth. Females only lactate for 2 to 3 months and do not nurse young that are not their own. The young have recurved cusps on their deciduous teeth. This allows the young to grasp the nipple of the females in order to prevent detatchment in flight. Mothers will stay with their young for 12 months after the young are flying on their own. This is also when most will fly in family groups of two or three when returning to their day roost. The day roosts may not always be the same place, allowing the young bats to learn how to seek out the vocal calls when the colony swarms around the chosen day roost sight. Males do not care for offspring.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); extended period of juvenile learning