Chapter 6

An Overview of the Primates

Chapter Outline Characteristics of Primates Primate Adaptations Primate Classification 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.

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

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. The brain has expanded in size and become

increasingly complex.

Binocular Vision in Primates

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 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. Most have four types of teeth: incisors,

canines, premolars and molars.

Primate Locomotion Most are quadrupedal, using all four limbs

in their locomotion. Arm swinging is found among the apes. Prehensile tails, found only among the

new world monkeys, are used as an aid to locomotion.

Alternative Classifications of Great Apes and Humans

Revised classification

(more evolutionarily accurate)

Traditional

classification

Great apes—separate family (Pongidae)

Orangutan

Gorilla

Chimpanzee

Bonobo

One family only (Hominidae), including all

large-bodied apes and humans; more detailed

distinctions made at lower taxonomic categories

Humans—separate family (Hominidae)

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).

Lorises Found in tropical forests and woodlands of

India, Sri Lanka, southeast Asia, and Africa. Characteristics:

Use a climbing 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. 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.

Hominoids(Apes and Humans) Characteristics distinguishing hominoids from

monkeys: Larger body size Absence of a tail Shortened trunk More complex behavior More complex brain 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. males = 200 lbs, females = 100 lbs Pronounced sexual dimorphism. Solitary Principally frugivorous (feed-eating).

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.

Three reasons: Habitat destruction Hunting for food Live capture for export or local trade

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.

Quick Quiz

1. Which of the following is NOT a primate characteristic?

a) stereoscopic vision

b) highly developed sense of smell

c) orthograde or upright posture

d) prehensility

Answer: b A highly developed sense of smell is

NOT a primate characteristic.

2. Binocular vision in primates contributes to

a) color vision.

b) lateral vision.

c) panoramic vision.

d) stereoscopic vision.

Answer: d Binocular vision in primates contributes

to stereoscopic vision.

3. Which of the following is NOT true of tarsiers?

a) They are nocturnal.

b) They are insectivorous.

c) They live in groups of 10-12 individuals.

d) They can rotate their heads almost 180 degrees.

Answer: c Tarsiers do not live in groups of 10-12

individuals.

4. The _________________ is the largest living primate.

Answer: gorilla The gorilla is the largest living primate.

5. Which of the following is NOT a reason that nonhuman primates are endangered?

a) habitat destruction for logging, mining, and agricultural land

b) hunting for food

c) live capture for either the exotic pet trade or biomedical research

d) establishment of biological reserves

Answer: d The establishment of biological

reserves is NOT a reason that nonhuman primates are endangered.