Chapter 7 Primate Behavior

Chapter Outline Primate Field Studies The Evolution of Behavior Why Be Social? Primate Social Behavior Reproduction and Reproductive Strategies Mothers, Fathers and Infants

Importance of Primate Studies Modern African apes and humans last shared a common ancestor between 5 and 8 m.y.a. Only within the last 4 decades have nonhuman primates been studied. Many species, such as arboreal monkeys have scarcely been studied at all.

Primate Socioecology Socioecology studies the relationship between social behavior and the natural environment. One assumption is that components of ecological systems evolved together. To understand how one component works, it is necessary to determine the species relationships with their environment.

Environmental Factors Quality and quantity of foods Distribution of food resources, water, predators and sleeping sites Activity patterns (diurnal, nocturnal) Relationship with other species Impact of human activities

Socioecology and Predation Environmental factors influence on group size and structure. Multimale and multifemale groups have an advantage when predation pressure is high. Adult males may join forces to attack predators. Savannah baboons have been known to kill domestic dogs and attack leopards and lions. Solitary foraging may be due to distribution of resources or predator avoidance.

Evolutionary Perspective Natural selection acts on behavior just as it acts on physical characteristics. Behavior is a phenotypic expression and genes code for specific behaviors. Natural selection has a role in shaping primate behavior.

Criticism of the Evolutionary Perspective Little data on: The social behavior of large groups of animals. Genetic relatedness through the male line. Assigning reproductive costs and benefits to particular behaviors. The genetics of primate social behavior.

Dominance Status Factors that influence status: Sex Age Aggression Time in the group Intelligence Motivation Mother’s social position.

Communication Raised body hair is an example of an autonomic response. Vocalizations and branch shaking are examples of deliberate communication. Reassurance is communicated through hugging or holding hands. The fear grin, seen in all primates, indicates fear and submission. Displays communicate emotional states.

Primate Social Strategies

Affiliative Behaviors Grooming reinforces social bonds. Hugging, kissing and grooming are all forms used in reconciliation. Relationships are crucial to nonhuman primates and the bonds between individuals can last a lifetime.

Patterns of Reproduction In most primate societies, sexual behavior is tied to the female’s reproductive cycle. Permanent bonding 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) Male competition for mates and mate choice in females are both examples of sexual selection.

Mothers 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. Monkeys raised without a mother were not able to form lasting affectional ties. The mother-infant relationship is often maintained throughout life.

Factors Influencing Evolution of Primate Behavior