Making and Having Babies

Grey-headed bat with babyWith so many different species of bats, it's not surprising that they have many different ways of reproducing. 

  • Most bats have only one baby - called a pup - at one time. But there are exceptions; the red bat, for instance, may have twins, or even three or four pups at once!
  • Most  bats, including those in temperate areas like New England, only give birth once a year.
  • Bats' range of mating systems is wide, ranging from monogamy to promiscuity. Some are polygynous, with males mating with multiple females and even forming harems. Sometimes the males form leks; they hang around together near the females and put on shows to impress the ladies. They vocalize and flap their wings, and some raise patches of hair to show how vigorous and desirable they are.
  • Bats in temperate areas generally mate in the fall but pups are not born until spring when there is plenty of food available. Some of the females store the sperm over the winter; others delay implantation; in still others the development of the pup is slowed until spring and favorable conditions.
  • There is also great variety in social systems. Some bats live solitary lives. Fruit bats in the family Pteropidae usually hang out together in large groups. Many bats, especially in temperate regions, form maternity colonies; the females all roost together with their pups. This helps to keep the babies warm and offers protection - strength in numbers. The sizes of colonies differs in different bats; there may just be a few bats or tens of thousands and everything in between.

Photo by Piotr Naskrecki of grey-headed bat, Pteropus poliocephalus