Intergroup relations Baboons and Mangabeys

DEFINITION 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

Home range / Territory 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 (?). Strier 2003; Cheney 1987, In Primate Societies

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.

aggressive 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.). 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. Cheney 1987, In: Primate Societies, Chicago UP. This raises the problem of estimating encounter rates.

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). Cheney 1987, In Primate Societies Intergroup dominance often determined by group size, and the number of adult males in that group (e.g. baboons, macaques). Not common when territorial.

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

Sex differences ? female dispersalNOT In those primate species characterized by female dispersal, females tend NOT to participate in intergroup encounters. Cheney 1987, In Primate Societies males are hostile toward members of other groups, especially other males 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.

Sex differences ? male dispersalaggressively 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 ! Cheney 1987, In Primate Societies Males antagonism mostly against other males. Related to the defence of females ! Ex: langurs, macaques, baboons, geladas.

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) Gorillas: NO Vervets: YES

SiamangChimpanzeeOrangutanGorilla Relative size of core area Distance traveled per day in relation to size of core area YesNo Core areas defended? Wrangham (1979) Soc Sci Info

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

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

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

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

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

Geladas T. gelada (xeric habitat)

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

Savannah baboons P. anubis (eating meat: gazelle)

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

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

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

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

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

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

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

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

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

Cercopithecus mitis Blue monkeys, Kakamega (Cords 2002 Behaviour)

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

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

Female-male friendships

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

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).

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.

Male-male relations: Dominance !

Old “friends” Agonistic buffering

Intergroup relationships Xenophobia +/- territoriality

Chimpanzee Baboon PhilopatryMale Female FM bondsNone Strong FF bondsWeak Strong MM bondsStrong Few Chimpanzee / Savanna baboon social structure compared

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