All Beasts Suckle? 

　　Beasts have hairs on their bodies. They are of vivipara and homeothermal animals that can act nimbly. Beasts are higher animals with the most complicate body structures, functions and behaviors among all vertebrates. The most outstanding feature of beasts is that they suckle their young, so they are all called mammals. The most primitive mammal lives in Australia; the duckmole, it is of ovipara, but the adults suckle their young with milk. They are also beasts.