05.12.17

Did you know that bats are incredibly good mothers? Strong and dedicated, these batty moms will have you seriously impressed!

1. Bats break the rules

In mammals, a general rule of thumb is the smaller you are, the higher the number of offspring and the shorter the duration of your pregnancy. However, bats are a complete exception to this rule. They not only have few offspring per pregnancy, but they also have pregnancies that can last up to seven months.

2. Bats have long pregnancies.

For bats, pregnancy duration is often related to the diet of the species. Insectivorous bats have shorter pregnancies lasting around three months, while pregnancy in frugivorous species lasts around five months. Vampire bats have one of the longest pregnancies of all bat species, with the young taking seven months to develop inside their mothers. Bat pregnancies are extremely long for such small animals, where most species weigh less than 70 grams. It also raises a big conservation issue as their long pregnancies and few offspring make it difficult for populations to recover threats such as disease, habitat loss, human-caused fatalities.

Hoary bat with twins. Courtesy of MerlinTuttle.org

3. Baby bats are HEAVY

Baby bats, called pups, can weigh up to a third of their mothers body weight when born. Their mothers bellies can become so big that is possible to see the pup moving under the skin. Because of the proportionally large size of the pup, most bat species only have one pup a year, or occationally twins. The genus Lasiurus is a rare exception. Bats like the hoary bat, Lasiurus cinereus, can give birth to up to four babies at a time. Imagine having to fly around with four!

4. Mother bats are strong!

Females are so dedicated to the task of motherhood that to cope with the challenges of pregnancy and carrying their young, their anatomy and behaviour are slightly different than males. In some species, females have wings with different shapes than males that allow them to generate more lift to fly. This also saves them energy during pregnancy and while carrying the pups. Also, as lactation is an exceedingly demanding process, females during this period usually spend more time than usual searching for food to cover the energetic costs related to milk production.

5. Pups need to hang on!

Pups are born with big hind limbs in comparison with the rest of their bodies, which in some species can be as big as their mothers hind limbs. These big feet help them cling to her during flight. This is an extremely important skill to have as a fall would lead to almost certain death. That is why they use not only the feet, but also their teeth to bite the nipples of their mothers and stay attached during flight. Ouch!

6. Pups have a lot of learning to do

Although bats give birth to big pups, they are considered altricial animals, which means that after their pups are born, they still require an incredible amount of care, development and learning until they are actually able to survive by themselves. This is not surprising as bats are very social animals that use complex systems of navigation and finding food requires a lot of learning and development.

7. Raising a pup – it takes a colony!

Raising a pup is a big job! However, most parental care, if not all of it, is left for the females with only few monogamous species where both parents share the job of raising young. In some cases, bat mothers like the the greater spear-nosed bat, Phyllostomus hastatus, form colonies where females take care of the offspring of other females while the mothers fly outside the roost to look for food. However, these colonies can have several thousand individuals. So how do bat mothers find their young when they come back? Female bats are believed to use echolocation calls and sometimes smell to find their offspring. Even so, it might be an incredibly hard task!