A hopping mouse is any of about ten different Australian native mice in the genus Notomys. They are rodents, not marsupials, and their ancestors are thought to have arrived from Asia about 5 million years ago.
All are brown or fawn, fading to pale grey or white underneath, have very long tails and, as the common name implies, well-developed hind legs. Half of the hopping mouse species have become extinct since European colonisation. The primary cause is probably predation from introduced foxes or cats, coupled with competition for food from introduced rabbits and hoofed mammals. A hopping mouse's primary diet is seeds. An Australian hopping mouse can concentrate urine to as high as 10,000 mOsm/L (10-20 times higher than a human). This allows it to survive in the desert without drinking water.