Vampire Bats ReproductionReproduction; the mating game. For vampire bats, mating occurs all year long, there is no specific “mating season”. Roosting sites provide the mating opportunity because the bats gather there in large numbers. The mating takes place while roosting upside down in the caves. Once the bats have mated, the sperm from the male will combine with the egg to form a embryo. This embryo will develop inside the female until it is ready to be delivered.
About 8 months after forming (a really long gestation period for a bat), the female will deliver the baby. Vampire bats will typically only have one baby. When the time comes to deliver it, the female will cling to the ceiling of the cave, head up and tail down. She will hang by her thumbs and curl up the tail membrane to form a pouch. Then, the tiny and furless baby will drop out of the mother’s body and into the pouch.
At birth, the newborn will weigh about .17 ounces to .25 ounces. In about 25 days, the weight will have doubled, and in about 120 days, the weight will have quadrupled. Young vampire bats are dependent of their mothers for as long as 9 months. Males take no part in the care of the young.
Now, unique again to other species of bats, vampire bat young are very lucky. For the most part, females with pups are present all year long. This means that other females are able to look after the young of others. This happens often, and other females will often nurse the young of other bats. Oftentimes, if a pup is orphaned, another female will “adopt” it.