1. HERDS Simple aggregations... or cooperative groups?

2. Basic categories of animal interactions

3. Spermophilus lateralis Spermophilus armatus Spermophilus columbianus Grades of social structure (ground squirrels) Female territory male territory

4. Marmota flaviventris Cynomys ludovicianus Grades of social structure (ground squirrels)

5. Packs of up to 40, consisting of a breeding pair (alpha male & female) that mate for life, plus non-breeding offspring of several generations. Strict social hierarchy, maintained by ritualized display and fighting among lower ranking members Wolf (Canis lupus) -- dominant pair, extended family Alpha female suppresses reproduction in lower ranking females Non-breeders help rear young.

6. Wolf (Canis lupus) Maintain large territories defended against other packs. Pack size and social cohesion is dependent on resource base. Non-breeders often disperse. Cooperative hunting of large game Food sharing

7. Lion (Panthera leo) cooperative females, male exploiters Prides up to 40 individuals – related adult females, dependent young, and 1 male, or a male group (often related). Multiple adult females reproduce. Sexually dimorphic, males 40% bigger. Males are dominant, but there is generally little aggression except during pride takeovers.

8. Females cooperative in hunting large prey and in rearing young (“communal” nursing). Lion (Panthera leo) Resident male(s) remain in control until killed or evicted during pride takeover by another male or coalition. New males kill dependent cubs (to bring females into estrus) and evict any older immature males. Females stay with their natal pride, young males are expelled near puberty. They become solitary or form male “coalitions” (usually groups of related males).

9. Spotted hyena (Crocuta crocuta ) Female social dominance Clans of up to 100 individuals, predominantly related females and dependent offspring. Fewer adult males. Multiple females breed. Some cooperative hunting, but often individual. Lots of aggression during feeding Communal dens, but no communal rearing of young

10. Females are entirely dominant over males. The youngest lowest status female is dominant over the highest ranking male. Spotted hyena (Crocuta crocuta) The extreme aggression and large size of females has involved hormonal “masculinization”. Including male-like external genitalia. This causes mechanical difficulties in reproduction (both copulation and birth) Cubs aggressive from birth, with competition & siblicide involved in establishment of social hierarchy.

11. Meerkat (Suricata suricata) autonomous collective Bands of up to 30 individuals, both sexes, no apparent social hierarchy. Forage individually within a cohesive group. Band defends territory against other bands. Multiple breeding pairs. Females stay with natal group, males tend to disperse. Cooperative anti-predator vigilance (sentinels). Food sharing. Cooperative breeding (baby sitting and nursing).

12. African elephant (Loxodonta) Stable matriarchy Herds of variable size up to 20 animals, including related adult females and their dependent young. Led by a “matriarch” (oldest female). Females stay with natal group, males leave at puberty. Female groups very stable – travel and forage together, strong mutual defense. Cooperative care of young. Males are solitary or form separate bachelor herds. Promiscuous mating

13. Mantled howler monkey (Alouatta palliata) Troops of variable size (up to 20). Multiple adult females form the stable social core. Not all are close kin. 1-3 males. Social hierarchy is linear, with males dominant, but top ranks fluctuate. Territorial -- troop boundaries and spacing determined through male vocalization Young of both sexes disperse from natal groups to form or join other groups. Mating promiscuous. Male mating success dependent on rank. Males form alliances to achieve rank and acquire mating opportunities.

14. Yellow baboon (Papio cynocephalus) Troops of variable size (up to 100). Related females and dependent young with multiple adult males. Males substantially larger than females. Females stay with natal group, and form stable social core with dominance hierarchy. Female rank is inherited. Males leave natal troop to join others. Male hierarchy very dynamic determined by age structure. Dominant male aggressively guards females in estrus. Males form fighting alliances to achieve rank. Low ranking “strange” males socialize strongly with females. Mating promiscuous, often solicited by females who prefer strangers.

15. Common Chimpanzee (Pan troglodytes) Variable group size, mulit-male multi-female group. Groups are ‘fusion-fission”. Female sexual swellings: promiscuous mating. In bisexual groups, males form the social core and are dominant within a strict hierarchy. Males remain with natal group, females may disperse. Male-male alliances are formed to establish rank and to increase mating success. Alliances not always based on kinship. Males engage in lethal raids involving incursions into neighboring groups.

16. Killer whale (Orcina orca) Pods of variable size, consisting of one or more subpods (female kin groups with dependent young), and adult males. Several pods may form larger less cohesive clans. Females seek non-pod members as mates. Males seek to mate outside their kin-group pods Cooperative hunting, wide range of cohesive behaviors Both sexes stay within pods. Stable social hierarchy.

17. Sperm whale (Physeter macrocephalus) Pods of variable size, stable core of female kin plus dependent young. Multiple females breed. Extreme sexual dimorphism – adult males much larger reflecting male competition for access to females. Young males form bachelor herds. Adult males solitary, or associate with females seasonally. Intense male competition for mating opportunities. Female cooperative behavior – baby sitting during adult feeding dives, mutual defense, variety of cohesive social behaviors, including individualized sounds for identification.

18. Summary of social group patterns Banded mongoose (Mungos mungo) Matriarchal social organization multi-generation female kin groups, Rarity of male/female pair bonding Social roles of males and females differ, males are often “asocial” or even “antisocial”

19. EVOLUTION OF SOCIAL SYSTEMS What are the advantages? Ultimately, increased fitness (genetic survival) either Directly – through offspring and decendants Indirectly – through direct fitness of kin Reproductive success is dependent on age (young animals gain inclusive fitness by remaining with mother to help raise younger sibs) Social systems arise when: Resources are limited (cooperative group foraging) Cooperative social behavior usually involves kin selection (“nepotism”) Greater efficiency in resource use Reproduction (finding mates, cooperative rearing) societies are formed around kin groups strongest cooperative interactions involve close kin

20. Subterranean colonies of up to several hundred males and females. One reproductive female (queen), one or more reproductive males and many non-reproductive animals of both sexes – multiple generations of offspring. Strict social hierarchy, distinct castes, with division of labor. Queen suppresses reproduction in subordinates through pheromones. EUSOCIALITY the most extreme social structure Naked mole rats (Heterocephalus glaber)

21. Soldiers (both sexes) NON-REPRODUCTIVE CASTES Workers (both sexes Queen Male consorts (1-3) Dispersers (both sexes) leave to establish new colonies REPRODUCTIVE CASTES Specialized functional castes

22. Mole rat “queen” (and workers) Breeding females Non-breeding females and males Reproductive specialization – increased fecundity

23. Basic categories of animal interactions ALTRUISM – helping another at a cost to oneself Altruistic behavior usually involves kin and includes a “selfish” component through kin selection (increasing inclusive fitness)

24. Helping unrelated individuals Reciprocal Altruism – helping with the expectation of future return. – involves “sharing” Example – male fighting alliances cooperation between unrelated males to gain (and share) mating access Example -- food sharing in common vampires (Desmodus rotundus) Bottlenosed dolphin (Tursiops truncatus)

25. Common vampire (Desmodus rotundus) Small stable groups of 8-12 bats, adult female and dependent young. Adults within a group have mixed kinship, some are non-relatives. Males solitary or in “bachelor groups”. Promiscuous breeding, Dominant males defend breeding territories that include 1 or more female groups.

26. BUT mortality is low, because of food sharing Common vampire (Desmodus rotundus) Obligate blood feeders – after a blood meal water is excreted rapidly leaving a stomach full of concentrated blood Cannot survive more than 48h without food. Feeding success is variable, largely dependent on age and experience. Young bats may have failure rate of 33%, so there is a high probability of missing a meal for two consecutive nights

27. Females will share food with their semi-dependent young. (extended maternal care) between related females (I.e., kin selection) Adult females also form stable “sharing partnerships” of two categories: Food sharing in the common vampire (Desmodus rotundus) between unrelated adults – reciprocal altruism After returning to the roost, females groom each other to determine who has fed successfully and to solicit food sharing through regurgitation.

28. Food sharing in the common vampire (Desmodus rotundus )

29. How can reciprocal altruism between non-relatives evolve? The cost to the donor must be relatively small compared to the benefit to the recipient Reciprocity (the reversal of donor-recipient roles) must occur over short time periods, in the same “currency” “Cheaters” must be identified and punished!