Intergroup relations Baboons and Mangabeys

1. Intergroup relations Baboons and Mangabeys

2. Home range: Area exploited by a group of primates (defended but not exclusively) Overlap between home ranges Territory: Area exploited and EXCLUSIVELY defended by primates No overlap between territories DEFINITION

3. Non-territorial primates defend a clumped, desirable food source, such as large fruiting trees. Ex: capuchins, red howlers, baboons, mangabeys, great apes These species require large home ranges, relative to their day ranges (distance travelled in one day). They cannot keep intruders out of their home range at all times. No overlap in territories. Possible to defend EXCLUSIVELY a territory if the day range is roughly the equivalent of the radius of their home range. Ex: gibbons, ring-tailed lemurs, tamarins, dusky titis, red-tailed monkeys (?), blue monkeys (?). Home range / Territory Strier 2003; Cheney 1987, In Primate Societies

4. Home range / Territory Relationships between home range and other factors: • The home range increases with species body weight • Range increases with group size, both within and among species. • Terrestrial primates have larger home ranges than arboreal primates • Frugivores have larger home ranges than folivores Rodman 1999, Ann. R. Anthropol.

5. Intergroup relations Intergroup relations are clearly aggressive, although sometimes they are not. For instance: red-tailed monkeys in Kibale NP (Uganda). Sometimes they are, sometimes they are not (pers. obs.).

6. Intergroup relations Problem of definition: Cheney and Seyfarth (1977) defined it for baboons as any approach of one group within 500 m of another. Inappropriate for primates with small home range / territory. This raises the problem of estimating encounter rates. Cheney 1987, In: Primate Societies, 267-281. Chicago UP.

7. Intergroup dominance When home ranges overlap extensively, and are not defended, the aggressive defence of a resource (like a fruiting tree) may be costly. -> Avoidance of other groups (Intergroup Dominance). Intergroup dominance often determined by group size, and the number of adult males in that group (e.g. baboons, macaques). Not common when territorial. Cheney 1987, In Primate Societies

8. Sex differences ? Since female reproductive success appears limited primarily by energetic and nutritional constraints, female grouping patterns are influenced by food distribution. Thus females are predicted to be more aggressive toward females of other groups than toward males, or males toward males of other groups. Cheney 1987, In Primate Societies

9. Sex differences ? • In those primate species characterized by female dispersal, females tend NOT to participate in intergroup encounters. • In contrast, males are hostile toward members of other groups, especially other males. Such hostility seems to be related to the defence of females. • Ex: chimpanzee, gorilla, red colobus. Cheney 1987, In Primate Societies

10. Sex differences ? • In those primate species characterized by male dispersal, females participate aggressively in intergroup encounters (almost all Old World monkey species). • Female antagonism mostly against other females, sometimes against males. Related to the defence of food ! • Males antagonism mostly against other males. Related to the defence of females ! • Ex: langurs, macaques, baboons, geladas. Cheney 1987, In Primate Societies

11. Gorillas: NO Vervets: YES Q. 4: WHY DEFEND A TERRITORY? Strier 2007 Hypothesis: Territorial behavior (defense of an area) depends on “economic defendability”. “Economic defendability” depends on a low cost of defense (long day-range: small home-range)

12. Siamang Yes Chimpanzee No Orangutan No Gorilla No Relative size of core area Distance traveled per day in relation to size of core area Core areas defended? Wrangham (1979) Soc Sci Info

13. Average day-range (path-length) = r ID = Index of Defendability = r/d Core area or Home range Diameter = d

14. ID < 1 ID > 1 Lepilemur mustelinus Lemur catta Indri indri Propithecus verreauxi 0 Territorial Callicebus (moloch, torquatus) Cercopithecus (aethiops, mitis, ascanius) Colobus guereza (Dunbar) Presbytis entellus (Yoshiba) Hylobates lar Symphalangus syndactylus Alouatta palliata Macaca mulatta, radiata E. patas Lemur fulvus, mongoz Cercocebus albigena Alouatta seniculus Theropithecus gelada NON- territorial Saimiri oerstedi Papio anubis, cynocephalus Miopithecus Colobus guereza (Oates), badius Presbytis entellus (Jay) Papio ursinus Gorilla gorilla Pan troglodytes Pongo pygmaeus

15. Baboons and Mangabeys Share a recent common ancestor Part of the Afro-papionins : savannah baboon, drill and mandrill, gelada, and hamadryas, mangabeys Confusion between two groups of mangabeys : Cercocebus and Lophocebus are paraphyletic Now Cercocebus Mandrillus Theropithecus Lophocebus Papio Another confusion = taxonomy of savannah baboons From the same genus or not? Yes (Groves 2001). No (Jolly 1993) Overall approx. 12 species of Afro-papionins

16. Mangabeys - Lophocebus L. aterrimus L. albigena (feeding on figs (F. sansibarica)

17. Mangabeys - Cercocebus C. torquatus (self-grooming) C. galeritus (feeding on yellow palm fruits)

18. Geladas T. gelada (xeric habitat)

19. Hamadryas baboons P. hamadryas (hybrid zone with P. anubis)

20. Savannah baboons P. anubis (eating meat: gazelle)

21. Savannah baboons P. cynocephalus (AM protecting infant) P. ursinus P. papio (AM following AF-oestrus)

22. Baboon social organization Stable troops >10 females > 5 males

23. “Savanna” baboons Hamadryas baboons (one-male units) Anubis, olive Yellow Henzi & Barrett (2003) Evol Anthropol

24. Savanna baboon social structure F-F: Strong alliances, dominance F-M: Friendships (increases F reproductive rate) M-M: Dominance, some coalitions Intergroup: Xenophobia +/- territoriality

25. Female-female dominance= stable, based on mother’s birth rank

26. Agonistic relationships among females have few reversals. Laikipia anubis. Barton and Whiten (1993)

27. High-ranking (female) baboons eat more Laikipia anubis. Barton and Whiten (1993)

28. Females care about rank reversals between more than within families Okavango (Bergman et al. 2003)

29. Female dominance hierarchies don’t always predict success Cercopithecus mitis Blue monkeys, Kakamega (Cords 2002 Behaviour)

30. Cercopithecus mitis Blue monkeys, Kakamega (Cords 2002 Behaviour)

31. But: sociality can be more important than rank (in promoting RS) Amboseli Silk et al. 2003

32. Grooming time is a measure of friendship. But, it also responds to interest of infants. Chacma baboons, South Africa, Barrett & Henzi 2002, Behaviour

33. Female-male friendships

34. Defining ‘Friendship’ between Female and Male. (1) Spatial proximity. Use ethograms to score dyads (range 0-20). For most FF, top M scores ‘10’; the rest scores <3. (2) Grooming. Record all grooming bouts. For average F, top M = 65% of her grooming. (3) Defining a ‘Friend’. ‘Friend’ = high score on BOTH proximity & grooming.

35. Characteristics of F-M ‘Friendships’ (1) Approaches by Female. To Friends: routine (feed, groom, travel) To non-Friends: submissive, present, appease. (2) Duration. Similar age (often start as adolescence) Could be lifelong. (3) Distribution. FF: 1-2 M Friends (FF sharing a M were also friends). MM: 0-8 F Friends (high-rank MM had more F friends).

36. Benefits of F-M ‘Friendships’ (F1) Protection. >90% of MM protecting a F were Friends. (F2) Baby-sitting. Intolerant of infants except Friends’. (M1) Paternity. Increased present and future probability of paternity. (M2) Agonistic buffers. Friends, especially infants, can be used as social buffers.

37. Male-male relations:Dominance !

38. Old “friends” Agonistic buffering

39. Intergroup relationships Xenophobia +/- territoriality

40. Baboon Chimpanzee Female Philopatry Male Strong FM bonds None Strong FF bonds Weak Few MM bonds Strong Chimpanzee / Savanna baboon social structure compared

41. “The study of social behavior is no substitute for the study of social relationships.” Robert Hinde (1981)