Monkey, primate, ape; the terms slip so easily off the tongue, but just what do they mean, and how do they differ? And what does it mean to talk of New World and Old World monkeys?
Scientists and naturalists love terminology and taxonomy; somehow they fulfill a deep-seated desire to bring order to a messy universe. Being able to put a name to a creature gives us a sense of connectedness — even if we know nothing about the species in question.
The science of classification had been given a bad name by dusty old university professors, but the British science writer Colin Tudge has given it a new lease of life with his wonderful book “The Variety of Life” (OUP; 2000) — a survey of every organism that has ever lived.
Being a primate himself, Tudge has given them a thorough review. They include a wide range of fascinating families. Most primitive are the prosimians, which include the lorises, pottos, bush babies and the various lemurs. These are amazing but little-known creatures, many of which are nocturnal. They have a reflective layer at the back of the eye called a tapetum that reflects light at night (like cats’ eyes) and they are distinguished by their heightened sense of smell; they have cool damp noses (like dogs). They also have various other more esoteric differences from the higher primates, but to observe these you would have to investigate their skeletal features, the arteries that supply their brains, and the anatomy of their ears. It’s all technical stuff, but it’s fascinating to primatologists.
Higher primates lack the damp nose and the tapetum, both differences that are indicative of their greater reliance on sight during daytime. These are the primates that can be sub-divided into those dwelling in the New World and those of the Old World. New World primates include the diminutive marmosets and tamarins, the large, noisy howlers, the appealing squirrel monkeys and capuchins, and the long-limbed spider monkeys. The Old World primates include groups such as the macaques, baboons, guenons, and colobines (such as the nasally over-endowed proboscis monkey).
It is among the Old World primates that we find the apes. The graceful gibbons, long-armed and small-bodied, that hurtle through the Asian forest canopy, are known as the lesser apes, but it is the great apes that we empathize with more readily. The great apes are the gorillas, the chimpanzees, the hominids (that’s us and our extinct relatives), and the orangutans.
“Monkey” is a nontechnical term that generally refers to the New and Old World primates, excluding the prosimians and the apes, though apes are sometimes incorrectly referred to as monkeys. One animal that fits most people’s image of a monkey is the common squirrel monkey. This delightful creature lives in noisy groups that move restlessly through a home territory. They are inquisitive and dexterous as they peel aside leaves, searching out insects.
Whereas such species fit the popular image of a monkey, others don’t. And wouldn’t it be rude to call a huge male orangutan in the prime of life, complete with his massive cheek flanges and arms as long and as strong as your legs, a “monkey”? He might just take offense.
New and Old World primates differ not just in the presence or absence of tails and the extent to which they can use them, but also in the visible features of their noses. The nostrils of New World primates face outwards, while those of the Old World primates face forward or down. So when you are next staring a “monkey” in the face, if you find that you can see right into both nostrils at the same time, then you are looking at an Old World primate. As for the characteristics of Old World primates, just take a look at the end of your fingertips — we have flattened nails in common.
The smallest of the New World primates is the doll-like pygmy marmoset. These tiny creatures, even as adults, weigh only about 120 grams. Compare that with 175 kg for an eastern lowland gorilla with its sumo-wrestler proportions. Marmosets are the mammalian equivalent of hummingbirds. They dash about, they have high-pitched calls, and they live life neurotically on high-energy drinks. Like hummingbirds, marmosets will sip nectar — though they also chew gum. Nearly 70 percent of their diet consists of the saps and gums exuded by tropical trees. So if your parents or spouse complain about your gum-chewing habits, you can always try claiming a long gum-chewing ancestry. These marmosets, like hummingbirds, live high-speed lives, but only briefly — they are lucky to make it to 12 years old, whereas their heavyweight distant cousins, the gorillas, can hope for 50.
In Japan there is one native representative of the Old World primates — the Japanese macaque — though this species experiences mixed fortunes here. In some places, it is indulged and fed, while elsewhere, it is persecuted as a farm pest. Some are caught for medical research, while others have been shipped overseas to zoos and collections. The final insult now is that someone with no understanding of the uniqueness of island species has released the endemic Formosan rock macaque (naturally restricted to Taiwan) into Japan. Their presence has led to a number of cases of hybridization, and now Honshu Island macaques must add genetic degradation to the various other problems they face.
Japanese macaques have been long studied in these islands, and they make fascinating subjects. Among the primates, only humans range farther north. Japanese macaques are able to cope with climates ranging from the subtropical humidity of Yakushima south of Kyushu, to the frigid winters with heavy snowfalls of the Shimokita Peninsula, at the very north of Honshu. Perhaps only the langurs of the Himalaya inhabit such a wide range of temperatures and climatic conditions.
The next time you meet some macaques, give a thought to their extraordinary range of achievements. Japanese macaques do not have prehensile tails, and they do not chew gum, brachiate, or bellow calls out across the forest canopy. Instead, they can swim, they take hot baths, they have developed cultural traditions such as washing certain foods. Where they have been introduced overseas, they have learned which local species of plants are palatable and they have developed a new alarm call used only for rattlesnakes. They even use natural forms of medicine.
And some people call them monkeys.