Why female kangaroos have pouches
What is the function of a kangaroo's pouch and how small is a newborn joey?
Marsupials wouldn’t be marsupials without pouches. Their very name derives from the Latin for “pouch”: marsupium.
Like all marsupials, kangaroos are born at a remarkably early stage of development.
A newborn joey is little more than a mouth and a muscular pair of forelimbs attached to a bean-sized body, which perfectly equips it for its first challenge in life – to haul itself through its mother’s fur and latch onto a teat in her pouch, where it will complete its development.
The marsupial pouch probably started out as a simple fold of skin to protect the helpless young while they suckled in a nest.
The squirrel-like phascogales, or wambengers, have a similar system today. But most marsupials developed more voluminous structures, allowing mothers to carry their dependent young with them in safety at all times.
Please note external videos may contain ads:
There is, however, one semi-aquatic freshwater species. The South American water opossum has a strong sphincter muscle around the pouch opening, which can be tightened to form a watertight seal.
Intriguingly, male water opossums also have a pouch, although this is used not to carry the young, but to protect the genitals when diving.
Main image: Female kangaroo with a joey in her pouch. © Westend61/Getty