This is Sassy, a Common Wallaroo, and her at foot joey Voomp. Voomp is taking the opportunity to have a drink while mum is standing still!

What's amazing though is that there is another smaller joey inside Sassy's pouch, that is drinking a totally different milk to Voomp.

Macropods have four teats inside the pouch. When a joey is born it climbs from the cloaca to the pouch and attaches itself to a teat. This is the same teat it will drink from until it is weaned. As the joey grows the milk composition changes with it.

As a macropod joey grows the carbohydrate levels in the milk increase until the joey emerges and then there is a rapid decline. Similarly, the concentration of lipids gradually increases, but in contrast this rises sharply when the joey emerges. Protein also increases during lactation.

Interestingly, a macropod can produce two totally different milk formula's for two different joeys at the same time. Voomp has his own teat in Sassy's pouch, the teat would have been streched so that he can easily reach it while standing outside the pouch. The other joey inside Sassy's pouch is suckling from another shorter teat (they stretch as the the joey grows) with a different milk composition entirely.

Now that's pretty clever!