Most are terrestrial and have four legs. However, some mammals live in the sea and have fins.
The smallest is the hong-nosed bat, which weighs 0.05 ounces. Bats are the only mammals that can fly because they have wings. The largest is the blue whale, which can weigh 150 tons. But wether they live on land or water, all mammals share some common characteristics.
Mammals can be carnivorous, herbivorous and omnivorous. Mammals are viviparous. After they are born, young mammals feed on their mothers' milk. Alba Valle Montoyo y Martín Romo Alday, 4° de Primaria.