Primate Social Organization & Behavior

1. Primate Social Organization & Behavior Advantages to living in social groups: • Safety in numbers • Knowledge base (food, skills, etc.) • Support in raising young • Readily available mating partners • Social bonds help alleviate conflict

2. Composition of Group Determined By: • Distribution of resources • Constraints of habitat • Threats from predators • Competition within and between species • Many species are territorial

3. Variation in Primate Social Structure • Solitary (mostly prosimians, but also the Orangutan) • Monogamous pairs (not very common among mammals) • Large, permanent social groups • Single male, multi-female or • Multi-male, multi-female

4. The mother-infant bond • Foundation of the social group • Infant is completely dependent on mother for: • Nourishment • Transportation • Protection • Opportunity for social learning

5. Learning How to Behave • Primates gather important social info from visualsignals which • Convey info about: • Age • Sex • Rank • Reproductive status

6. Visual signals: Age • Coat color of babies dif. from adults

7. Visual Signals: Rank • Dominant male gorilla has silver colored hair = silverback

8. Differences between Males & Females • Sexual dichromatism • Males & females of same species have dif. color hair • Sexual dimorphism • Differences in body & tooth size • Sexual divocalism • Differences in calls & sounds made by males & females

9. Visual signals: Reproductive Status • Females only sexually receptive during most fertile period known as estrus • Signaled by bright pink/red & swollen genitals Ischial callosities

10. Maximizing Reproductive Success • Is individualistic • Reproductive “strategy” – behavior that enhances an individual’s reproductive success • Differs for males and females

11. Infanticide as a Reproductive Strategy Among Hanuman Langurs • Bachelor males raid established group • Fight w/dominant male • Infants are killed • Triumphant male takes over • Brings females back into estrus • Ensures babies are his Langur infanticide

12. Primate Dominance Hierarchies • System of ranking in which there are low ranking (subordinate) and high ranking (dominant) individuals • Rank based on individual’s ability to displace, intimidate, or defeat other group members through contests Dominance = preferential access to resources (both food and mating partners) • Rank is not permanent (changes throughout life) • Sex • Age • Time in group • Level of aggression (challenging or “displaying”) • Intelligence (Mike the chimp rolling cans in camp) • Mother’s social position

13. Primate Dominance Hierarchies, cont. • Actually reduce violence within the group • Associated with distinct behaviors & gestures • Facial expressions communicate important social information

14. Grooming • Most important social activity • Pleasure of physical contact • Reinforces social bonds and status • Restores harmony • Helps form alliances

15. The New Chimpanzees Go to Video