The term “Old World monkey” refers to the primates that make up the taxonomic family known as “Cercopithecidae“; they are mostly spread across Africa and Asia.
Cercopithecidae consists of 23 genera and 160 species and includes various types of monkeys such as baboons, macaques, colobuses, langurs, and more.
The family is split into two subfamilies: Cercopithecinae, which has 78 species, and Colobinae, which has 82 species.
Characteristics of Old-World Monkeys
Here are the main characteristics shared by Old World monkeys:
Diet
The majority of the species in the Cercopithecinae subfamily are omnivorous; although the specifics vary by species, they generally feed on foods like fruits, leaves, insects, small animals, eggs, and more[1]. On the other hand, all of the species of the Colobinae subfamily are herbivorous; their diets primarily consist of leaves and seeds [2].
Explore more on: What Do Monkeys Eat?
Gestation
Depending on the particular species, the gestation period of Old-World monkeys is usually around 5 to 7 months[3]. In most cases, these monkeys have one child per pregnancy; however, there is a small chance of double births occurring[3].
Tail
All Old-World monkeys have tails, though they are non-prehensile, meaning they cannot be used to hold or grasp objects[3]. It should also be noted that Old-World monkeys possess pads known as “ischial callosities” on both sides of their tail (on the rear)[4]. These pads of tissue can make sitting down on branches and other rough surfaces easier.
Body Size
Old-World monkeys are generally medium-to-large-sized. The smallest species are the northern and southern talapoin monkeys, typically weighing about 2 to 3 pounds[5]. On the other hand, the largest species is the mandrill-males generally weigh around 55 pounds once they reach adulthood[6]. It is quite common for male species of Old-World monkeys to be much larger than their female counterparts.
Teeth
All Old-World monkeys (as well as apes and humans) share the same dental formula of 2.1.2.3[7]. This essentially means that each quadrant of the mouth has 2 incisors (which are used to bite food directly) and 1 canine (which is used to tear food), as well as 2 premolars and 3 molars (both of which are used to chew food).
Social Behavior
All Old-World monkey species are very social—most of them spend the majority of their lives with a group of their species[8]. Commonly, females stay with the group they were born in for their entire lives, while males often leave to join another group once they have grown up. For this reason, the social groups of Old-World monkeys are matrilineal; females typically make up the majority of these groups.
Eyes
Old-World monkeys all have trichromatic vision, the type of vision humans have—which means that their retinas have three different types of light-sensitive cone cells: red, green, and blue[3]. The ratio of the amounts of each of the three colours controls the final color seen.
Limbs
Old-World monkeys are quadrupedal, meaning they mainly walk on all four legs. It is also worth mentioning that, unlike their New-World counterparts, these monkeys have fully opposable thumbs, which helps them firmly grasp things in their hands[9].