Female kangaroos can also store all the bits needed to make babies for over three years before combining them...it's a survival thing for living in the desert or in arid lands.

Fascinating, isn't it? I learned that kangaroo's for example don't waste energy because they use their legs a bit like springs on a pogo stick so they can travel long distances with a minimum amount of effort hence less food requirement = energy. Yup they're well adapted to survive harsh desert conditions.