UPSC » UPSC CSE Study Materials » Biology » Terrestrial Primates

Terrestrial Primates

Terrestrial primates are primates that live on land. Though they are similar to regular primates, there are a few differences. This article contains notes on terrestrial primates.

Primates are an order of mammals. Animals in this category have prehensile hands and feet, i.e., hands and feet that can easily grasp objects. Opposable thumbs are also common amongst primates. Common primates include gorillas, chimpanzees, lemurs, monkeys, and humans. 

What are Primates?

‘Primate’ is a term used to describe a specific group of mammals. It is the third most diverse order of mammals and comprises more than 250 species. Their ancestors lived in tropical forest trees. This explains many of their characteristics, particularly those that help them adapt to the harsh and complex tree-living environment. 

Primates are generalist mammals. Their bodies can achieve almost anything. Their skeletal structure is such that it allows for a wide range of movement. This is manifested in how they move: some walk – on two legs or four legs, some climb, others leap, some even brachiate (swing from branch to branch). 

Terrestrial Primate Meaning

A terrestrial primate is a primate that primarily lives on land. Even though these primates spend most of their lives on land, they still have certain characteristics that can enable them to climb trees. 

The most well-known examples of terrestrial primates include gorillas, baboons, and humans. Other than their movement, terrestrial primates are similar to their arboreal (tree-climbing) counterparts. Except for humans and gorillas, terrestrial primates usually sleep in the trees and not on the ground. Tree-climbing is seen as an activity you do purely for fun, not survival. 

Humans are easily the most distinct primates. Not only are they terrestrial, but also highly intelligent. 

Primates as Compared to other Mammals 

Primates are quite different from other mammals. Compared to other terrestrial animals, primates have larger brains. Their brains also have a unique fissure – the Calcarine Sulcus. This fissure separates the two sides of the brain and the first and second visual areas on each side. 

Most mammals have hooves or claws on their digits (dogs, wolves, etc.). Primates, however, have flat nails. Their extremities are also relatively unspecialized. This enables primates to carry out a wide variety of functions and actions. 

The few primates with claws also have a flat nail called the hallux on their big toe. This hallux diverges from the other toes and can work together to form a pincer. This pincer can then be used to grasp several objects, branches foremost.

Primates have teeth that are very distinct from other mammals. The low, rounded shape of their premolar and molar cusps is remarkably different from the elaborate ridges and high, pointed cusps of other mammals. 

Their opposable thumbs are one of their most distinctive characteristics. However, many incorrectly believe that all primates possess an opposable thumb. In reality, only some primates have dexterous hands. Other than the most obvious examples – humans, apes, and monkeys – this includes lorises and lemurs. 

Primates share some similarities with other arboreal mammals. This includes dermatoglyphics (skin ridges that make fingerprints possible), grasping feet (also found in squirrels), and specialised nerve endings (increase our tactile sensitivity). 

Primates and Movement 

Different primates move in different ways. There are four main types of movement that primates employ. These are as follows:

Leaping

Leaping is a type of movement carried out using hind legs. Primates who use leaping as a movement tend to weigh less than 10 kg. Their elongated hind legs help them increase the distance and height of their leaps and exert less muscle force in their movements. Lemurs, galagos, and tarsiers are the primates most known to move via leaping.

Brachiation 

This movement involves using the forelimbs to swing from one branch or tree to another. Apes and spider monkeys have developed limbs that help them engage in this arm-swinging and arms hanging activity. They have long forelimbs that allow for increased arm-swinging. Unlike primates that do not swing, apes also have more hook-like and longer fingers. 

Climbing

Though climbing is one of the options available to primates, it is easily the least used movement type as opposed to the other three. The other methods of locomotion are far more common. 

Climbing is divided into vertical climbing, bridging, and clambering. It is the latter two that are far more common in primates. Clambering involves moving through a network of branches. Bridging involves the primate stretching across a gap and then pulling to the other branch. Orangutans and lorises use this technique.

Quadrupedalism

This final movement type is the one most commonly used by terrestrial primates. Quadrupedal primates have limbs of equal length – both fore and hind. However, their joint mobility throughout their limbs is significantly lesser, and pronated hand positions (palm facing downwards) are more common. 

Like climbing, terrestrial quadrupedalism can also be divided into three subcategories: knuckle-walking, fist-walking, and digitigrade. Knuckle-walking, exhibited by gorillas, is when the fingers are folded at the first joint and the back angled at 45°. Fist-walking, exhibited by orangutans, involves moving with your fingers closed in a fist and supinated foot positions (outward). Finally, baboons use digitigrade hand positions, where they walk on the flats of their fingers. 

Conclusion

Primates are an important part of our world and one of the many types of animals that inhabit the earth. Even though humans are the most developed primates, the others also carry great importance. Their unique characteristics, particularly their ability to grasp objects, set them apart from all other mammals and make them worth studying.