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Chapter 7

Textbook Chapter 7 Notes

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University of Toronto Mississauga
Heather Miller

Notes From Reading CHAPTER 7:PRIMATE B EHAVIOR (PGS. 145-172) Learning Objectives  Explain how it’s possible for natural selection to act on behavior  Describe the many similarities between human and nonhuman primate behavior  Explain why primatologists say that many nonhuman primate species have culture  Describe the ways in which we humans are unique among primates and the ways in which we aren’t Introduction  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 result of conscious decision making The Evolution of Behavior  Ecological – pertaining to the relationship between organism and all aspects of their environment (temperature, predators, nonpredators, vegetation, availability of food and water, types of food, disease organisms, parasites, etc.)  Behavioral Ecology – the study of evolution behavior, emphasizing the role of ecological factors as agents of natural selection. Behaviors and behavioral patterns have been favored because they increase the reproductive fitness of individuals (ie. they are adaptive) in specific environmental context  Behaviors are adaptations to environmental circumstances that existed in the past as well as in the present  Behaviors have evolved thought the operation of natural selection  therefore subject to natural selection the same way physical traits  In insects and other invertebrates, behavior is genetically controlled; they’re innate  But in birds and mammals, behavior is learned however some behavior are at least partly influenced by hormones  Behavior must be viewed as the product of complex interactions between genetic and environmental factors  One of the major goals of primatology is to discover how certain behaviors influence reproductive fitness and how ecological factors have shaped the evolution of those behaviors  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 Some Factors That Influence Social Structure Body Size  Larger animals require fewer calories per unit of weight than smaller animals because larger animals have less surface area (relative to smaller animals)  Since body heat is lost at the surface, larger animals can retain heat more efficiently, so they need less energy overall  Example: Two 10-pound monkeys need more food than on 22-pound monkey Basal Metabolic Rate (BMR)  Metabolism – chemical processes within cells that break down nutrients and release energy for body to use  BMR is concerned with the rate at which the body uses energy to maintain bodily functions while in a resting state (metabolism)  Smaller animals have a higher BMR than larger ones  Larger primates, which tend to have lower BMR and reduced energy requirements relative to body size, can do well with less energy rich foods (ie. leaves) Notes From Reading CHAPTER 7:PRIMATE B EHAVIOR (PGS. 145-172) Diet  Need to consider benefits of energy (calories) derived from food items against costs of ingesting and digesting them  Smaller-bodied primates focus on high-energy food, larger one don’t necessarily need to Distribution of Resources  Species that feed on abundantly distributed resources may live in one-male groups and later be able to join with others to form large, stable communities  Some species that depend on food distributed in small clumps are protective of resources, especially if their feeding area is small enough to defend  Some live in small groups of a mated pair or a female with one or two males and dependent offspring Predation  Depending on their size, primates are vulnerable to many types of predators including snakes, birds or prey, wild dogs and other primates  Their response to predation depend on their body size, social structure and type of predator  When predation pressure is high and body size is small, large communities are advantageous Relationships with Other, Non-Predatory Species  Many primate species associate with other primate and nonprimate species for various reasons including predator avoidance  When they share habitats with other species, they exploit somewhat different resources Dispersal  Another factor that influences social structure and relationships within groups  Individuals who disperse usually find mates outside their natal group  Has led primatologists to conclude that the mots valid explanations for dispersal are related to two major factors: o Reduced competition between males for mates o The decreased likelihood of close inbreeding Life Histories  Life History Traits – characteristics and developmental stages that influence reproductive rates  Examples that include life history traits are the length of gestation, length of time between pregnancies, period of infant dependency and age at weaning, age at sexual maturity and life expectancy  Shorter life histories are advantageous to species that live in marginal or unpredictable habitats because reproduction can occur at a relatively rapid rate  The slow rate of reproduction increases the threat of extinction  Example: for great apes are being hunted at a rate that far outpaces their replacement capacities Activity Patterns  Most primates are diurnal and some New World primates are nocturnal  Nocturnal primates tend to forage for food alone or in groups of two or three and many hide to avoid predators Human Activities  All nonhuman primate populations are now impacted by human hunting and forest clearing  These activities severely disrupt and isolate groups, reduce numbers, reduce resource availability and eventually can cause extinction Why Be Social?  The costs of competition are offset by the benefits of predator defense  Primates may live in groups for predator avoidance  Group living evolved as an adaptive response to a number of ecological variables and it has served primates well for a long time Notes From Reading CHAPTER 7:P RIMATE B EHAVIOR (PGS. 145-172) Primate Social Behavior  All of these behaviors have evolved as adaptive responses during more than 50 million years of primate evolution Dominance  Many primate societies are organized into dominance hierarchies  Dominance Hierarchies – systems of social organization wherein individuals within a group are ranked relative to one another o High-ranking animals have greater access to preferred food items and mating partners than lower-ranking individuals  Dominance hierarchies usually serve to reduce the amount of actual physical violence  Individual rank or status can be measured by access to resources, including food items and mating partners  Primatologists think that the primary benefit of dominance is the increased reproductive success of high-ranking animals  High-ranking females also have higher reproductive success because they have greater access to food than subordinate females  An individual’s position in the hierarchy isn’t permanent and changes throughout life  It is influenced by man factors including sex, age, level of aggression, amount of time spent in the group, intelligence, perhaps motivation and sometimes the mothers social position  All primates learn their position in the hierarchy  Dominance and sub dominance are indicated by gestures and behaviors  Early contact with their moths and subsequent exposure to peers, young primates learn to negotiate their way through the complex web of social interactions in their daily lives Communication  Communication – any act that conveys information, in the form of a message, to another individual. Frequently, the result of communication is a change in the behavior of the recipient. Communication may not be deliberate but may instead be the result of involuntary processes or a secondary consequence of an international action  Autonomic – pertaining to physiological responses not under voluntary control. o An example in chimpanzees would be the erection of body hair during excitement. Blushing is a human example. Both convey information regarding emotional states, but neither is deliberate, and communication isn’t intended  Body posture can provide information about an animals emotional state  Among many primates, an intense stare indicates a mild threat  Other threat gestures are a quick yarn to expose canine teeth  Primates also use a variety of behaviors to indicate submission, reassurance or amicable intentions  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  Vocalizations play a major role in primate communication  Primate (and other animals) also communicate through displays  Displays – sequences of repetitious behaviors that serve to communicate emotional states. Nonhuman primate displays are most frequently associated with reproductive or competitive types of behavior o Examples include chest slapping in gorillas and, in male chimpanzees, dragging and waving branches while charging and threatening other animals Aggressive Interactions  Affiliated Behaviors – amicable associations between individuals. Affiliative behaviors, such as grooming, reinforce social bonds and promote group cohesion  Conflict within a group frequently develops out of competition for resources, including m
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