Since there are few trees or other obstacles to offer hiding places, mammals that live in the grasslands may learn to burrow to escape from predators or be able to flee quickly as a member of a herd. Both areas support large numbers of herbivores that move in herds. North American grasslands have hot summers and cold winters. Changing rainfall patterns limits the growth of trees in the area as well as the grass. In areas where there is more rain, the grass grows taller.
African savannas are generally drier than the grass- lands of North America .
The trees that dot the savanna are called acacia trees and are adapted for this dry environment by having small leaves, much like chaparral and desert plants.