Anthropology1- Chapter 7 Question

CHAPTER 7 Primate Behavior

What is Meant By Behavior?

• Anything organisms do that involves action in response to

internal or external stimuli.

• The response of an individual, group, or species to its

environment.

• Such responses may or may not be deliberate and they

aren't necessarily the results of conscious decision

making.

Ecological Perspective

• Pertains to relationships between organisms and

all aspects of their environment

• Temperature

• Predators

• Vegetation

• Availability of food and water

• Types of food

• Disease organisms

• Parasites

Behavioral Ecology

Focuses on the relationship between behaviors,

natural environment, and biological traits of the

species.

Based on the assumption that animals, plants, and

microorganisms evolved together.

Behaviors have evolved through the operation of

natural selection, or

Some behaviors are influenced by genes and are

subject to natural selection the same way physical

characteristics are.

The Evolution of Behavior

Behavior constitutes a phenotype

 Individuals whose behavioral phenotypes increase

reproductive fitness pass on their genes at a faster

rate.

Genes do not code for specific behaviors, but they do

code for biological factors that impact behavior, i.e.

hormone levels, intelligence

Species vary in their limits and potentials for learning

and behavioral flexibility, set by genetic factors.

Natural selection acts on genetic factors shaped by

ecological, the same as it does physical

characteristics

Social Structure

• The composition, size, and sex ratio of a group of

animals.

• The social structure of a species is, in part, the

result of natural selection in a specific habitat, and

it guides individual interactions and social

relationships.

Why Are Primates Social? • Group living exposes animals to competition with other group

members, so why not live alone?

• Costs of competition are offset by the benefits of predator

defense provided by associating with others.

• Group living evolved as an adaptive response to a number of

ecological variables.

Some Factors That Influence Social Structure

• Body Size

• Larger animals are better able to retain heat and their overall energy

requirements are less than for smaller animals

• This means they need fewer calories per unit of body weight.

Some Factors That Influence Social Structure

• Metabolism

• The chemical processes within cells that break down nutrients and release

energy for the body to use.

• Basal Metabolic Rate (BMR) and Diet

• Smaller animals generally have a higher BMR than larger ones.

• This means smaller primates require an energy-rich diet high in protein,

fats, and carbohydrates (fruit, and insects).

Some Factors That Influence Social Structure

• BMR and Diet

• Nutritional needs have evolved along with BMR and body size

• Benefits are considered in terms of energy (calories) obtained from food

versus costs (energy expended) of obtaining and digesting them.

• Larger primates consume large amounts of lower quality foods

Some Factors That Influence Social Structure • Distribution of Resources

• Leaves are abundant, dense, and support large groups of animals. (gorillas)

• Insects are widely scattered, causing animals to feed on them alone or in small groups of two or three (lorises, marmosets, tarsiers)

• Fruits and nuts occur in clumps and are most efficiently exploited by smaller groups of animals; large groups break up into smaller subunits to feed. (baboons, vervets, chimpanzees)

• These groups tend to be the most territorial due to the need and ability to defend limited food supply

Some Factors That Influence Social Structure • Predation

• Primates are vulnerable to many predators, including snakes,

birds of prey, leopards, wild dogs, lions, and even other

primates.

• Where predation pressure is high, large communities are

advantageous (safety in numbers).

Some Factors That Influence Social Structure

• Dispersal • Upon sexual maturity individuals leave their birth group

• Usually males disperse, but sometimes it is the females

• Dispersal decreases the chances of inbreeding, competition

for mates, and the likelihood of gene survival.

Some Factors That Influence Social Structure • Life Histories

• Characteristics or developmental stages of a species that have an impact on reproduction • i.e. length of gestation, time between pregnancies, period of infant

dependency and age at weaning, age of sexual maturity, and life expectancy.

• For example gorillas are not sexually mature until approx. 12, infant dependency is 3 to 5 years, even with a 35 year life span a female will only produce 3 to 4 offspring in her life

• Unpredictable environments (seasonal food supply) favor shorter life histories and stable ones (steady resources), longer lives

• Today, the slow rate of reproduction increases the threat of extinction for all the great apes.

Primate Social Behavior: Dominance

• Many primate societies are organized into dominance

hierarchies that impose order and establish

parameters of individual behavior.

• Higher-ranking animals have greater access to

preferred food items and mating partners than lower

ranking individuals.

• Dominance hierarchies are sometimes called “pecking orders” that change throughout one’s life and are learned

Factors that Influence Dominance Status

• Sex

• Age

• Aggression

• Time in the group

• Intelligence

• Motivation

• Mother’s social position

Primate Social Behavior: Communication

• Any act that conveys information to another individual.

• Frequently, the result of communication is a change in the

behavior of the recipient.

• Communication may be the result of involuntary

processes or a secondary consequence of an intentional

action.

Communication • Raised body hair is an example of an autonomic, or

unintentional, response.

• Gestures, facial expressions, scent marking and vocalizations are examples of deliberate communication.

• Grooming serves to indicate submission or reassurance.

• Displays communicate emotional states.

Primate Communication

• The fear grin, seen in all primates, indicates fear and submission. • Often misconstrued by humans as a greeting!

• Threat yawns are a warning and are also seen amongst many primates

Primate Social Behavior: Affiliation and Altruism

• Common affiliative behaviors include reconciliation,

consolation, and interactions between friends and

relatives.

• Hugging, kissing and grooming are used in reconciliation.

• Relationships are crucial to nonhuman primates and the bonds between individuals can last a lifetime.

• Altruism, behaviors that benefit another while posing risk to oneself, are common in primate species.

Grooming • Picking through fur to remove dirt, parasites, and other materials

that may be present.

• Social grooming is common among primates and reinforces

social relationships.

• Grooming is also used to show submission/ appeasement or

reaffirm the pecking order

Primate Social Behavior: Aggressive Interactions

• Are disruptive to the group and are typically avoided or

mitigated before harm is done.

• Conflict within a group frequently develops out of competition

for resources, including mating partners and food items.

• Most intragroup aggression occurs in the form of various

signals and displays within the context of a dominance

hierarchy.

• Most tense situations are resolved through various submissive

and appeasement behaviors.

Serious and Fatal Consequences of Aggression

• Dominant displays or actions are often linked to reproductive

success:

• Dominant female macaques can control the food supply of subordinates

leading to weight loss and poor nutrition, impacting their chances of

reproductive success

• Competition among males for mates can result in injury and death

Intergroup Aggression

• Primate groups are associated with a home range where they

remain permanently.

• The home range contains the core area where the best most

reliable food supply is, this is where the group is most often

found.

• Home ranges of different groups may overlap, but core areas

don’t. The core is said to be the groups territory, and it is the

area that is defended against intruders. (sometimes violently)

Reproduction and Reproductive Behaviors

• In most primate societies, sexual behavior is tied to the

female’s reproductive cycle--estrus.

• Permanent bonding between females and males is not common

among nonhuman primates.

• Male and female Bonobos may mate even when the female is

not in estrus, a behavior that is not typical of chimpanzees.

Reproductive Strategies

• Behavioral patterns that contribute to individual

reproductive success.

• Primates produce only a few young in whom they invest a

tremendous amount of parental care (K–selected)

(contrast r-selected)

• Male competition for mates and mate choice in females

are both examples of sexual selection.

Sexual Selection

• A type of natural selection that operates on one sex, usually males due to female “selection” of mates.

• Long-term, this increases the frequency of traits that lead to greater success in acquiring mates.

• Sexual selection produces dimorphism with regard to a number of traits, most noticeably body size. • This is due to competition, which frequently leads to physical combat, for

mates

Examples of Sexual Dimorphism The following traits are characteristics of the males only of many

of the great apes. Primarily gorillas, chimpanzees, orangutan • Not bonobos. Why?

• Sagittal crest: Allows for much more surface area for temporalis

and mastoid muscles which allows for a much more powerful

bite. This is used for combat and defense of territory and

females

• Canine-premolar (CP3) honing process: sharpens the canine

teeth, again needed for male combat and defense

Male gorilla skull (left) and female

(center) CP3 process (right)

/

Infanticide: A Reproductive Strategy?

• One way males increase their chances of reproducing is by killing infants fathered by other males.

• Individuals maximize their reproductive success, no matter the effect on population or species.

• When an infant dies, its mother resumes cycling and becomes sexually receptive.

• An infanticidal male avoids waiting up to two to three years for the infants to be weaned before he can mate with their mothers.

Hanuman langurs

Mothers, Fathers and Infants

• The basic social unit among all primates is the female and

her infants.

• Except in species in which monogamy or polyandry

occur, males do not participate in rearing offspring.

• The mother-infant relationship is often maintained

throughout life.

Primate Maternal Bonding

• Primate infants raised without a mother have been

found to not be able to create necessary social bonds,

to successfully copulate or productively raise their own

young

Primate Cultural Behavior

• Cultural behavior is learned; it is passed from

generation to generation through observation and

instruction.

• Nonhuman primate infants, through observing

their mothers and others, learn about food items,

appropriate behaviors, and how to use and

modify objects to achieve certain ends.

• More complex, chimpanzee culture includes tools

such as termite fishing sticks and leaf sponges.

• Cultural practices are unique to differing groups

Examples of Cultural Behavior

• Japanese macaques and sweet potato washing

• Orangutan nest building

• Gorilla depth testing

• Chimpanzee termite fishing, leaf sponges, hunting

“spears,” nut cracking

• Kanzi’s stone tool making

Anthropocentric

• Viewing nonhuman animals in terms of human motives,

and experience and capabilities; emphasizing the

importance of humans over everything else.

• This sets up a hierarchy that says humans are “better” or

the ideal state

Language

• Nonhuman animals haven’t been considered capable of communicating about external events, objects, or other animals.

• It has been assumed that nonhuman animals use a closed system of communication, where vocalizations don’t include references to specific external phenomena.

Language

• Vervet monkeys use specific vocalizations to refer to

particular categories of predators, such as snakes,

birds of prey, and leopards.

Kanzi • Kanzi, a Bonobo, began using symbols when he

was 21/2 years old and

his younger half-sister

began using symbols at 11

months old.

• Both went to training

sessions with their mother,

but neither had been

taught or were involved in

the sessions.

The Biological Continuum

• Human brains are larger than primate brains, but the neurological processes are functionally the same.

• The necessity of close bonding with at least one parent

• Need for physical contact

• Developmental stages and dependence on learning

• Capacity for cruelty, aggression, compassion, altruism, with humans more adept at cruelty and compassion and capability to reflect on behavior

Thinking About Humans

• How is social stratification similar to and different from the

dominance hierarchies found in many primate species?

• What patterns characterize human “dispersals”?

• How are primate aggressive behaviors similar to and

different from the violent actions that are present in

human societies?