As the only flying mammals, bat moms find themselves in a unique situation when it comes to lactation.
Bat mothers need to provide milk to their offspring. Bat mothers also need to fly to forage sites and find food for themselves.
A heavy load of milk has a substantially negative impact on a female’s ability to fly. It makes sense for bat moms to get rid of excess milk prior to heading out. This is known as the milk dumping hypothesis. It accurately describes how female bats can keep their milk production high while still efficiently foraging for themselves.
At peak lactation, a female evening bat can produce just over half her own body weight in milk per day.
This is a substantial amount of extra mass for an individual that needs to fly to find food.
If females who must forage and fly have older pups who aren’t drinking as much milk and are hunting for themselves, the bat moms must lose their extra milk-weight prior to setting out on a foraging excursion.
How is a mother supposed to lose her extra milk weight?
She provides this nutritious food resource to another pup in the communal den.
Allonursing in bats seems like a win-win situation. Bat moms use their excess milk to feed other pups in the roost. This ultimately functions to make the entire colony larger and stronger. Bat moms in larger roosts benefit from information and predator protection. Mother bats have the advantage of a continued milk supply to provide their older pups in case they are unsuccessful in foraging for themselves. The act of suckling by foreign pups keeps a bat mom’s milk supply strong.
This post is an excerpt from my book “Wild Moms: Motherhood In The Animal Kingdom.”
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