Because the system scientists use to classify animals can be confusing to the uninitiated, many people don’t realize that the gorilla is actually a member of the family of great apes. So the question isn’t how to tell the difference between apes and gorillas, but how to tell the difference between gorillas and other apes. However, it’s actually pretty easy once you know what to look for.
Make sure you can distinguish between apes and other primates. Of the 11 families of primates, only apes and monkeys are anthropoid (meaning they have body structures very similar to humans). Since monkeys have tails and apes don’t, it’s easy to tell them apart.
Know that there are two groups of apes. Gibbons, or lesser apes, are small (averaging about 15 lb.), and all the great apes are much larger. There are four species of great apes: gorillas, orangutans and two species of chimpanzee--the common chimpanzee and the bonobo, or pygmy, chimpanzee.
Look for the size difference between other apes and gorillas. Chimpanzees range from 88 to 143 lb., and orangutans weigh from 90 to 110 lb. Gorillas are much larger, ranging anywhere from 200 to 400 lb.
Check the hair color. Gorillas have brown hair, while the hair of chimpanzees is black and that of orangutans is reddish-brown.
Look at the head and face of an ape. Gorillas have large heads with small ears and eyes. Their foreheads bulge outward, and they have a crest of hair (called the sagital crest). Their canines (pointed teeth) are large. Chimpanzees have large ears and a protruding shout below a prominent brow ridge. Orangutans have prominent mouths and distinctive cheek flaps.
Another difference to look for is that gorillas are not good climbers and live on the ground. Chimpanzees climb well, and orangutans are arboreal, spending most of their lives scampering high above the forest floor.
Consider their diet. Chimpanzees and orangutans are omnivores and supplement the fruits and other plants they eat with small animals they catch. Gorillas are herbivores. Although they will occasionally eat insects, they are not meat eaters.