Chapter 6

An Overview of The Primates

Chapter Outline

Characteristics of Primates Primate Adaptations Primates Classification A Survey of the Living Primates Endangered Primates

Primates As Mammals

There are approximately 190 species of nonhuman primates

Primates belong to:– Vertebrate class - Mammalia – Subgroup of placental mammals.

Characteristics of Primates

Fur (body hair) Long gestation followed by live birth Homeothermy, the ability to maintain a

constant body temperature Increased brain size Capacity for learning and behavioral

flexibility.

Binocular Vision in Primates

Primate Limbs

A tendency towards erect posture. Hands and feet possess grasping ability. Features of the hands and feet:

– 5 digits on hand and feet– Opposable thumb– partially opposable great toe– Tactile pads enriched with sensory nerve fibers at

the ends of digits

Dental Formulae

Primate Senses and the Brain

Color vision is a characteristic of all diurnal primates, nocturnal primates lack color vision.

Depth perception is made possible by eyes positioned forward on the front of the face.

Decreased reliance on the sense of smell (olfaction).

The brain has expanded in size and become increasingly complex.

Primate Maturation

Longer periods of gestation Reduced numbers of offspring Delayed maturation Extension of the entire life span.

Primate Learning and Behavior

Have a greater dependence on flexible, learned behavior.

Tend to live in social groups. Males are permanent members of many

primate social groups, a situation unusual among mammals.

Arboreal Hypothesis

Arboreal (tree) living was the most important factor in the evolution of primates. – Prehensile hand is adapted to climbing in

the trees.– A variety of foods led to the omnivorous

diet and generalized dentition.

Visual Predation Hypothesis

Primates may have first adapted to shrubby forest undergrowth and the lowest tiers of the forest canopy.– Forward facing eyes enabled primates to

judge distance when grabbing for insects.– Flowering plants may have influenced

primate evolution.

Primate Habitats

Most live in tropical or semitropical areas of the new and old worlds.

Most are arboreal, living in forest or woodland habitats.

No nonhuman primate is adapted to a fully terrestrial environment; all spend some time in the trees.

Primate Diet and Teeth

Generally omnivorous, reflected in their generalized dentition.

Most eat a combination of fruits, leaves, and insects.– Some primates kill and eat small mammals.– Some primates are dietary specialists on leaves.

Most have four types of teeth: incisors, canines, premolars and molars.

Primate Locomotion

Most primates are quadrupedal, using all four limbs in their locomotion.

Arm swinging is found among the apes.– Siamangs of southeast Asia use this exclusively.– Monkeys that use a combination of leaping and

arm swinging are termed semibrachiators. Prehensile tails, found only among the new

world monkeys, are used as an aid to locomotion.

Human and Chimpanzee Chromosomes Human chromosome

2 has banding patterns that correspond to chimpanzee chromosomes 12 and 13.

This suggests that human chromosome 2 resulted from the fusion of ape chromosomesduring the course ofhominid evolution.

Revised PartialClassification of the Primates.

Alternative Classifications of Great Apes and Humans

Prosimians

The most primitive of the primates. Characteristics:

– Reliance on olfaction– Laterally placed eyes– Shorter gestation and maturation periods– Dental specialization called the "dental

comb”

Lemurs

Found on the island of Madagascar and other islands off the coast of Africa.

Extinct elsewhere in the world. Characteristics:

– Larger lemurs are diurnal and eat vegetable foods: fruit, leaves, buds, and bark.

– Smaller lemurs are nocturnal and insectivorous (insect -feeding).

GeographicalDistribution of Modern Lemurs

Lorises

Found in tropical forests and woodlands of India, Sri Lanka, southeast Asia, and Africa.

Characteristics:– Use a climbing form of quadrupedalism.– Some are insectivorous; others supplement their

diet with fruit, leaves, gums, and slugs.– Females frequently form associations for foraging

or in sharing the same sleeping nest.

Tarsiers

Small nocturnal primates found on the islands of southeast Asia.

Characteristics:– Eat insects and small vertebrates which

they catch by leaping from branches.– Basic social pattern appears to be a family

unit consisting of a mated pair and their offspring.

Anthropoids(Monkeys, Apes and Humans) Common traits:

– Larger brain and body size– Reduced reliance on the sense of smell– Greater degree of color vision– Bony plate at the back of the eye socket– Different female reproductive anatomy– Longer gestation and maturation periods– Fused mandible

Monkeys

Represent about 70% of all primate species.

Divided into two groups separated by geography and several million years of evolutionary history:– New world monkeys– Old world monkeys

New World Monkeys

Almost exclusively arboreal. Found in southern Mexico and central

and south America. Two families: Callitrichidae and Cebid

New World Monkeys: Callitrichidae Give birth to twins Live in families composed of a mated

pair or a female and two adult males, plus the offspring.

Males are involved with infant care.

New World Monkeys: Cebid

Possess prehensile tails. Most live in groups of both sexes and all

ages. Others live as monogamous pairs with

subadult offspring.

Old World Monkeys

Habitats range from tropical forests to semiarid desert to snow-covered areas in Japan and china.

Characteristics:– Most quadrupedal and arboreal– All belong to the Cercopithecidae family:

• Divided into subfamilies, the cercopithecines and the colobines.

Geographical Distribution of Modern Old World Monkeys.

Hominoids (Apes and Humans)

Characteristics distinguishing hominoids from monkeys:– Larger body size – Absence of a tail– Shortened trunk– More complex behavior– More complex brain and enhanced cognitive

abilities– Increased period of infant development and

dependency

Gibbons and Siamangs

Found in the tropical areas of southeast Asia. Adaptations for brachiation may be related to

feeding while hanging from branches. Diet is largely fruit with leaves, flowers, and

insects. Basic social unit is a monogamous pair and

their offspring. Males and females delineate their territories

with whoops and “songs”.

Orangutans (Pogo pygmaeus)

Found in heavily forested areas of Borneo and Sumatra.

Almost completely arboreal. Large

– males = 200 pounds– females = 100 pounds

Pronounced sexual dimorphism. Solitary Principally frugivorous (feed-eating).

Geographical Distributionof Modern African Apes

Gorillas (Gorilla Gorilla)

Largest of the living primates. Confined to forested regions of central Africa. Males can weigh up to 400 pounds, females

200 pounds. Primarily terrestrial, using a posture called

“knuckle –walking”. Groups consist of one large silverback male,

a few adult females, and their subadult offspring.

Chimpanzees (Pan Troglodytes) Found in equatorial Africa. Anatomically similar to gorillas particularly in

limb proportions and upper-body shape. Locomotion includes knuckle-walking on the

ground and brachiation in the trees. Eat a variety of plant and animal foods. Large communities of as many as 50

individuals.

Bonobos (Pan paniscus)

Only found in an area south of the Zaire river. Population is believed to only number a few

thousand individuals. Exploit the same foods as chimps, including

occasional small mammals. Male-female bonds constitute the societal

core. Sexuality includes frequent copulations

throughout the female's estrous cycle.

Humans (Homo Sapiens)

The only living species in the family Hominidae.

Human teeth are typical primate teeth. Dependence on vision for orientation to

the world

Humans (Homo Sapiens)

Flexible limbs and grasping hands Omnivorous diet Cognitive abilities are the result of

dramatic increases in brain size. Bipedal

Endangered Primates

Over half of all living primates are endangered, many face immediate extinction

Most primates live in tropical rain forests that are being destroyed for their natural resources.

Some primates are hunted for their meat. Others are victims of the exotic pet trade.

Tropical Rain Forests of the World (Before Recent Massive Destruction)

Hunting of Primates

In West Africa the most serious problem is hunting to feed the growing human population.

Estimated that thousands of primates, are killed and sold for meat every year.

Primates are also killed for commercial products.

Conservation Efforts

Many developing countries have designated areas as national parks or reserves.

Private organizations, such as the rain forest information center in Ecuador, have set up biological reserves.

Through conservation and educational programs, primate species may have a chance at escaping extinction.