Primate Locomotor Patterns

A)   Lemurs, specifically those who fall under the suborder Strepsirhini, live in the eastern rainforests of Madagascar, an island off the Southeast coast of Africa.  Although there are over 100 species of lemurs, this specific species called the Ruffed Lemur prefers to live in the crowns of large and tall trees, where they remain throughout the four seasons of the year.  This choice of elevated habitat is most suitable because this part of the rainforest receives vast amounts of rain each year.  This is an ideal location for the lemurs because fruit, flowers, and young leaves are ample and can be eaten during the warm seasons, while mostly flowers, leaves, and bark are consumed during the colder seasons.  Lemurs consume as many as 132 different plant species.  Fruit and nectar make up the highest percentage of the lemur’s diet.

B)   The most common locomotor patterns of lemurs include quadrupedalism, which refers to locomotion in which an animal uses all four legs/limbs.  Lemurs also leap, cling, suspend, bridge, and utilize bimanual and bipedal movements.  Lemurs are considered both terrestrial (on land) and arboreal quadrupeds (a primate that use their four limbs to move through trees).  Leaping is the predominant method lemurs use to move through trees.  Although some primates use their tails to grip branches, lemurs instead rely on their limbs for movement and they utilize their tails as a balancing apparatus.

C)   The lemur’s pattern of locomotion has been greatly influenced by its environment.  For example, it has had to adapt to living in trees due to the immense rainfall that occurs in their habitat each year.  Because lemurs regularly move through treetops, their limbs have developed in order to allow them to leap branch to branch, run and bound through the trees, and also walk on the ground.  Because lemurs are capable of moving seamlessly both on land and through the trees, they are able to enjoy a more diversified diet due to the large areas available for foraging.

A)   Spider Monkeys are part of the parvorder: Platyrrhini.  This order of primates includes five families, which can be found in Central and South America and also in portions of Mexico.  Spider monkeys are a type of New World Monkey, which lives high in the tree canopies of the dense tropical rain forests.  The primary diet of the spider monkey includes fruit, nuts, honey, insects, flowers, bird eggs, spiders, bark, and small mammals, most of which can be found in the rain forest treetops.   It is very rare for a spider monkey to be seen on the forest floor.

B)   The Spider Monkey pattern of locomotion is characterized by the use of the animal’s four limbs and their tail.  Even without a thumb, this arboreal (tree living) species expertly swings through the dense canopy of trees utilizing their thin arms, legs, and tail.  When standing or walking on two feet, the spider monkey uses its tail for support. 

C)   The Spider Monkey’s environment has had a great impact on its locomotor patterns.  One example of the environmental impact is the development of the species’ prehensile tail.  This adaptation aids the spider monkey in climbing and gripping quickly to enable it to avoid prey and to compete with other animals for food.  Additionally, these monkeys have developed a bare patch or gripping area on the tail known as a friction pad, which allows for safer and faster mobility. 

A)            Baboons: All of the five different species of baboons live in Africa or Arabia.  Baboons generally live in semi-arid habitats like the savanna, yet some live in tropical forests.  Baboons spend most of their time on the ground, yet they sleep, eat, and watch for predators from the safety of the trees or rocky cliffs depending on their habitat.  The baboons of the savanna live in large troops, which are governed by a system of hierarchy.  Baboons forage for fruits, grass, seeds, bark, and roots, but they also hunt for meat and are known to eat birds, rodents, and sometimes livestock.

B)            Baboons walk quadrupedally on all four limbs.  Baboons do have tails but they are not prehensile, therefore the tail cannot be used as an additional hand.  Even without the use of a prehensile tail, baboons are able to climb into tree canopies to seek out food, sleep and avoid predators. 

C)            The environment has impacted the locomotor patterns of the baboon over time.  Since baboons are very large, they had to develop strong limbs that would enable them to climb and to move fast to escape predators, while also aiding them to fight off competitors.  Since baboon tails are not prehensile, this species relies solely on their legs and their arms for movement.  Also, since baboons walk on all fours, they have no free hands to carry the food that they forage.  As a result, a cheek pouch has developed into a specialized sac, which can be used to store foraged food.

A)        Gibbons are smaller apes that live in the dense forests of southern Asia, covering the region that stretches from China to Laos, northwestern Vietnam, Borneo, and even to India.  Gibbons are predominantly tree dwellers who use the forest canopy for safety and as their source of food.  Gibbons predominantly eat fruit, but they also tend to consume flowers, shoots, insects and leaf buds. 

B)        Gibbons use an interesting variety of locomotor patterns.  Their most common form of movement is brachiating, which allows them to move with an arm-swinging motion through the jungle at up to 35 miles per hour.  Brachiating also enables gibbons to swing and reach fruits that are at the end of branches.  Gibbons have also developed the ability to move bipedally.  When they are spotted on the ground, they often walk on two feet and swing their hands over their head for balance, since they have no tails to assist with this motion.

C)        The environment has greatly impacted the Gibbons’ trait expressions.  Because gibbons are the most threatened primates on Earth, they must seek safety in the forest canopies.  To move rapidly and efficiently through the dense forests, gibbons had to develop into brachiators, which are arm-swinging primates.  Another trait that developed due to their tree-dwelling lifestyle is the gibbons’ hook-shaped hands, which are used for grasping branches.  A third trait that arose in this species is their extremely long arms used to grasp faraway limbs, and their strong legs for propelling and grasping. These various traits allow for the speed, agility, and acrobatic movements the gibbons require for their survival. 

A)        Chimpanzees are primates that generally live in the rainforests, woodlands, dry savannas, and grasslands of Africa.  They tend to live in communities with several dozen other chimpanzees and animals.  A chimpanzee’s diet consists mainly of fruit, leaves, seeds, blossoms, stems, and even bark.  They sometimes consume insects, eggs, and some meats such as other monkeys.  Chimpanzees make use of both the ground as well as the trees, where they collect most of their fruit and build the nests they sleep in at night. 

B)        Chimpanzee’s patterns of locomotion include both quadrupedal knuckle walking and bipedalism.  Although this is true, they tend to do most of their walking on all fours.  The ability of chimpanzees to walk on four or two legs is incredibly useful when they use their hands to make tools.  Sticks are used by chimpanzees to remove insects from their nests, they use stones to smash open nuts, and they use leaves to drink water from.  All of these capabilities require chimpanzees to move bipedally.  Another function of chimpanzees being able to move bipedally is their ability to swing from branch to branch through the trees, where they gather most of their fruit and do most of their eating. 

C)        Chimpanzee’s locomotor patterns, which allow them to walk on all fours as well as on two feet, are the primary reason that these animals are one of the few that employ tools.  These tools allow chimps to break into food and eat while simultaneously standing on two feet.  Chimpanzees originally developed this trait so that they would be able to carry food and see over visual barriers in order to see predators and get a better view of their surroundings.  Another function chimps adapted due to these locomotor patterns is their ability to swing in the trees while gathering fruit, so that they do not have to walk as far and as long to get food and so they can carry their food while swinging through the trees. 

It is fascinating that in each instance, the aforementioned species all underwent trait alterations, which were triggered by forces in the environment. Some developed the ability to brachiate, others were able to alter their locomotion in order to transport goods or to utilize tools.  Gibbons and chimpanzees developed the capacity to bridge, which is the ability to stretch the body across two opposing branches.  Each new trait that develops empowers the apes to overcome challenges and dangers they face on a daily basis in their natural habitats, which, of course, is the basis of the Theory of Evolution by way of natural selection.  Clearly, the environment is one of the most dominant forces that causes the evolution of species by allowing for the elimination of traits that are unnecessary, and most importantly, by allowing other traits that are vital for survival to emerge.