The joeys, born on February 20 and March 13, have begun spending more time out of their mothers' pouches as they explore their surroundings.
The 10 and 11-month-old joeys will soon be too big to fit in their mothers' pouches, but will still stick their heads in to nurse until about 18 months of age, zoo officials said.
At birth, a joey is born at an underdeveloped stage and is the size of a jellybean. When born, the baby marsupial crawls up and into its mother's pouch without any assistance and then attaches itself to a teat, where it will remain for many months to grow and develop.
During this early stage of development, a mother produces low-fat milk for her young. As a joey gets older and ventures out of the pouch, the milk becomes high in fat.
The joey will continue to nurse for another nine months once it is out of the pouch.
If a mother kangaroo is nursing a newly born joey and a juvenile already out of the pouch, she has the ability to produce both low-fat milk and high-fat milk at the same time-- an attribute that zookeepers say is truly remarkable.
When the joey is 8 months old, it begins venturing out of the pouch more frequently.