Primary consumers are animals that eat producers, and since producers are almost always green plants, primary consumers can most simply be defined as herbivores, such as cows and deer. "Consumer" and "producer," in this usage, refer to the production and consumption of energy in a form that can be used for life processes. Ecologists talk of consumers and producers when discussing food webs in a particular place.
Possible examples of primary consumers differ based on the specific biome being discussed. On land, the large hoofed mammals, such as cattle, antelope and horses, and the massive African fauna, such as hippos and elephants, all readily come to mind as exemplary primary consumers.
There are, of course, numerous other land-based primary consumers, which are much smaller and less exotic. The mouse in the wall, the squirrel in the tree, and even the beetle eating sugar crumbs off the floor are examples of familiar primary consumers.
Fruit bats, hummingbirds and butterflies primarily consume plant material, and all are primary consumers, although they are not often thought of as plant-eaters.
In the ocean, primary consumers consist of the tiny shrimp and zooplankton that feed on algae and the many bottom-dwelling fish which nibble on plants.