Herbivores of the World

Think about the world's herbivores. In Africa, sleek, brown antelope roam the plains. In the United States, black-and-white spotted cattle graze in fields and provide milk and beef, while the arctic hare survives in the world's snowiest regions on barely any food at all. While not every herbivore looks the same, they do have some key characteristics in common.

  1. Energy Source

    • Unlike an omnivore, which eats anything, herbivores eat only plants and plants parts. A herbivore might eat nuts or seeds, but also things like the stem. Perhaps the most common food source for a herbivore is grass. To help their bodies process this food, most herbivores have specially adapted digestive systems that allow them to eat all sorts of plants -- even ones that could make other animals ill.

    Shapes and Sizes

    • One of the most fascinating things about herbivores is their disparate variety. For example, a cow is one of the world's most common herbivores. A Holstein cow is the one seen at county fairs and on television commercials: they're black and white or maybe red and brown. A baby Holstein can weigh 90 pounds at birth, and a mature Holstein can weight more than 1,500 pounds and stand 52 inches at the shoulder. But a squirrel is also a herbivore. Squirrels are barely more than a foot long and weigh only a few pounds. Just as we picture cows eating grass, we can see a squirrel with an acorn, making them both definitively herbivores.

    Time-Limited vs. Resource-Limited

    • Herbivores can be divided into two groups. In one group are time-limited herbivores, animals that have a strict time limit on gathering found. This explains why cows will graze all day, or why squirrels continue to gather nuts and seeds even after they're full. Time-limited herbivores do this for a number of reasons: A predator may come out at night, forcing it to hunt during the day, or a creature, like an owl, may actually see better at different periods of the day. Resource-limited herbivores are generally smaller than time-limited herbivores. A common example is an insect, which requires very little sustenance -- very few resources -- to survive.

    Food Chain

    • Assuming a traditional food chain, a herbivore is between plants and predators -- carnivores and omnivores. This means that a herbivore takes its energy from the plants, and the predators take their energy from the herbivore. Nearly all herbivores are prey. Some have developed defense mechanisms to guard themselves against predators. Some species form herds or packs, naturally playing to strength in numbers. Other animals have psychical defenses, like horns or antlers. Still others, like the tropical poison-dart frog and its ability to kill anything that eats it, have a more ingenious defense system.