Primates: Apes, Monkeys & Identification

Primates are defined by a set of features that reflect life in trees: grasping hands and feet, nails instead of claws on most digits, forward-facing eyes that give depth perception, and a brain size that — in many lineages — supports complex social behaviour and tool use. The order splits broadly into strepsirrhines — lemurs, lorises and bushbabies — and haplorhines, which include tarsiers, monkeys and apes.

Apes versus monkeys is the distinction most people need first. Apes — gibbons, orangutans, gorillas, chimpanzees and bonobos — lack tails and have broader chests and more upright posture. Monkeys have tails, though not all tails are equal: a howler monkey uses its prehensile tail as a fifth hand, while a baboon's tail is not grasping. Great apes share a recent common ancestor with humans; the conservation stakes for chimpanzees, gorillas and orangutans are therefore unusually direct — their forests are being cleared at a rate that outpaces protection.

How to recognise them

The features that separate this group in the field, in the order they are usually most useful.

Tail presence

Apes have no tail. Monkeys do, but only some New World monkeys have fully prehensile tails. Baboons and macaques carry non-grasping tails. A tail alone does not confirm a monkey — check the body plan.

Face and muzzle

Old World monkeys and apes tend to have narrower, more downward-facing nostrils close together. Most New World monkeys have wider, sideways-facing nostrils. Proboscis monkeys are the extreme case, with a large pendulous nose in males.

Locomotion

Gibbons brachiate — swing arm-over-arm beneath branches. Orangutans are largely arboreal and solitary. Gorillas and chimpanzees knuckle-walk on the ground. Lemurs often leap vertically between supports.

Size and build

Gorillas are the largest primates. Gibbons are small apes with very long arms. Tarsiers are tiny with enormous eyes and elongated ankle bones for leaping. Aye-ayes have rodent-like incisors and a long probing middle finger.

The confusion pairs

Ape versus monkey: no tail and broader chest in apes. Chimpanzee versus bonobo: bonobos are slimmer, more upright, with a central parting and pinker lips; chimpanzees are more robust with darker faces. Lemur versus monkey: lemurs have a wet nose and often a fox-like face; monkeys have dry noses.