Five Animals You Never Knew Make Milk for Their Babies

March 23, 2020

From The BBC:

We know how important milk is for babies. It is a rich blend of nutrients and protective chemicals that is essential for a baby's development.

In the entire animal kingdom, only one group of animals produce milk for their young: the mammals, the group we belong to. Mammalian milk is called "true milk".

However, a few other animals produce secretions for their babies that strongly resemble milk.

This "false milk" does not the look like cow or human milk, and nor is it produced the same way. But it serves the same purpose: it nourishes the animals' babies until they are old enough to fend for themselves.

Pigeons

Pigeons are great at sharing parenting duties. Unlike mammals, where only the female breastfeeds, males and females both produce "milk" for their young. This liquid is called "crop milk".

The crop is a sac-like structure at the base of a bird's neck, which they normally use to store and moisten food before digesting it. Two days before the pigeon eggs hatch, both the parents' crops become engorged with fluid-filled cells.

The pigeon parents regurgitate this thick milky goop into the mouths of their squabs. This crop milk remains the squabs' only food for several days after hatching.

Pigeon milk is extremely rich in proteins and fats. When it was fed to chickens in a 1952 study, their growth rate shot up by 38%.

A few other birds, like flamingos and emperor penguins, also produce crop milk.

Cockroaches

Yes, you read that right: some cockroaches feed their young a kind of milk. One such example is the Pacific beetle cockroach.

Most female cockroaches lay eggs in a sac called an ootheca, which they drop from their bodies before the eggs are about to hatch. After the young cockroaches hatch out of the eggs, they scamper about looking for food.

But the Pacific beetle cockroach female takes a different approach to childcare.

Instead of laying eggs, the embryos develop inside her brood sac, her version of a womb. Once the embryos have fully-formed guts, they start drinking "milk" produced by cells within the brood sac, and quickly put on weight.

Because the young cockroaches get a lot of nutrition while still within their mother's body, they are more developed and mature when they are eventually born.

To read more from The BBC, click here.