New World vs. Old World Monkeys
By Bri Vogel, Primates Incorporated Volunteer
To many, the word monkey means just one thing—some vine-swinging, tree-dwelling primate, usually brown and fuzzy and cute. But did you know that there are actually over 250 different species of monkeys? These species are divided into two main groups—Old World and New World monkeys. The term “old world” refers to the areas (Europe, Africa, and Asia) known to the Europeans prior to the discovery of the “new world” (the Americas). Old World monkeys are native to Africa and Asia while New World monkeys are indigenous to the Americas, but their homes are not the only ways in which they are different (3,4).
New World monkeys are members of five different primate families (Callitrichidae, Cebidae, Aotidae, Pitheciidae, and Atelidae) and consist of almost exclusively arboreal (tree-dwelling) species like marmosets, tamarins, capuchins, and spider monkeys (3). Old World monkeys belong to the family Cercopithecidae and consist of species such as macaques, baboons, and vervet monkeys (4). These monkeys spend much more of their time on the ground, but can be found in habitats ranging from the rainforest to the savannah to the mountains (2)!
One of the biggest differences between these two groups of monkeys is their tails. On one hand, some species of New World monkeys possess prehensile tails, meaning they can use their tails to grasp or hold on to objects (2). Their tails can aid these monkeys in finding and eating food in the canopy as well as moving amongst the trees, as their tails provide extra support and balance. On the other hand, Old World monkeys all have tails, but they lack the ability to grasp objects (2). However, some Old World monkeys have pads called ischial callosities surrounding their hind region (4). As these monkeys tend to spend more time on the ground than their arboreal New World counterparts, these calloused areas of skin provide support when they sit to feed or rest (2).
These two monkey groups also differ in a few other anatomical ways. New World monkeys have an additional premolar tooth in their mouths; they have three while Old World monkeys only have two (2). Old World monkeys have fingernails and toenails, while New World monkeys often have claws on all of their digits with the exception of the big toes of marmosets and tamarins (2,3). Another exception is the spider and howler monkeys— New World species with nails like Old World monkeys (2). Old World monkey thumbs are also more opposable and similar to our own (2). New World monkeys are also flat-nosed (platyrrhine) with nostrils further apart, while Old World monkeys have nostrils closer together and a nose which faces down (catarrhine) (2).
Another difference between these monkeys is the way they care for their young. In New World monkeys, it is common for the males to be involved in infant care (2). However, this is extremely rare in Old World monkeys; instead, the job belongs entirely to the females (2). Old World mothers also often carry their babies on their bellies, while New World babies will more commonly ride on their mothers’ backs (1).
Finally, these two groups of monkeys differ in the foods that make up the bulk of their diet. New World monkeys generally rely much more on fruit than Old World monkeys which instead focus more on leaves and grasses (2). Some even have specialized stomachs that can better break down the cellulose found in plants (3).
As you can see, even though these animals all share the title of “monkey,” they are more different than you might realize! Every species is unique and important in its own way.
Sources:
1. “Babies in the forest.” Monkeyland Primate Sanctuary. Retrieved from
http://www.monkeyland.co.za/babies-in-forest_article_op_view_id_331
2. “New World (American) and Old World (Africa and Asia) Monkeys: A Comparison.”
Cabrillo College. Retrieved from http://www.cabrillo.edu/~crsmith/monkeycomparisons.html
3. O’Neil, Dennis. “New World Monkeys.” Palomar College. 2012. Retrieved from
http://anthro.palomar.edu/primate/prim_5.htm
4. O’Neil, Dennis. “Old World Monkeys.” Palomar College. 2014. Retrieved from
http://anthro.palomar.edu/primate/prim_6.htm
Old World Monkey Species Example: Gray Langur
source: https://pixabay.com/en/gray-langur-monkey-india-langur-1213199/
New World Monkey Species Example: Cottontop Tamarin
source: https://pixabay.com/en/cottontop-tamarin-small-monkey-976527/