HEB 1330: Primate Social Behavior
Final Exam Study Guide
Lecture 1: Primate Sociality and Chimpanzees ............................................................. 1
Lecture 2: Intergroup relations and Baboons/ Mangabeys .......................................... 3
Lecture 3: Lemuriformes and Life History .................................................................... 5
Lecture 4: Phylogeny of Behavior and Sakis/Uakaris/Titis .......................................... 7
Lecture 5: Evolutionary History...................................................................................... 9
Lecture 6: Primate Diversity and Lorisoformes/Aotinae (Lemurs) ........................... 10
Lecture 7: Reproductive Endocrinology and Molecular Primatology....................... 11
Lecture 8: Sexual Selection and Gibbons ..................................................................... 12
Lecture 10: Food, Social Relations and Squirrel Monkeys ......................................... 15
Lecture 11: Feeding & Grouping/Social Relationships and Orangutans .................. 17
Lecture 12: Affiliation and Male Bonds and Gelada Baboons ................................... 28
Lecture 13: Competition and Cooperation and Tamarins .......................................... 29
Lecture 14: Mothering and Cercopithecines ................................................................ 30
Lecture 15: Childhood and Macaques .......................................................................... 31
Lecture 16: Communication, Vervets, Marmosets, and Baboons .............................. 32
Lecture 17: Cebus Monkeys and Cognition ................................................................. 34
Lecture 18: Predatory Behavior and African colobus monkeys ................................ 38
Lecture 1: Primate Sociality and Chimpanzees
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Introduction to Primate Studies:
Studies on brain size and:
o Sociality (positive relationship)
o Intelligence (Evol. Psychol.)
o Language (apes)
o Evolution (e.g. Homo erectus, cooking roots)
 Social animals
 Common ancestor
o Human prehistory
o Study of Evolutionary processes
 Conservation
Primate Social Structures
For females, the costs of grouping are expected to vary with differences in local resource
abundance and distribution.
The Chimpanzee
 First birth at 14-15 years
 Fission-fusion society
 Live to 60 + years in captivity, 50+? in wild
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Chimpanzee females forage alone because maybe the potential reproductive costs
of scramble and contest feeding competition are higher for them than they are for
males.
Males may be more willing to assume the costs of feeding competition to gain
mating opportunities and to derive social benefits from associating with other
males.
Closest ancestor to humans – similarities in behavior and culture including tool
use.
Classification of living genera in the primate order
Orangutan
Pongo
Pongidae
--------------------------------------------------------------Gorilla
Gorilla
Hominidae
Chimpanzee
Pan
Hominidae
Human
Homo
Hominidae
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Significance (2): behavioral principles
o Individual fission-fusion
 Focus on individual strategies
o Intergroup relations
 Predation unimportant?
 Large consequences
 Fission-fusion social system
o Temporary subgroups (“parties”) contain 1-20 or more individuals
o Mothers often alone; less gregarious
o Fruit supply: more fruit -> bigger parties
o “Estrous” females: sexual swellings -> bigger parties
o Bigger parties -> more hunts, patrols, aggression
 Parties are larger when fruit is more available
 Parties are larger when sex is more available (during swellings)
 Larger parties have more hunts
o No evidence that hunting is promoted by sexual opportunities
 Communities of 20-150 individuals
o Membership defined by common association
o Males more gregarious than females
o Males stay in natal group (except Bossou)
o Females usually emigrate at adolescence
o Males cooperate to patrol territories, attack neighbors, and hunt monkeys
Recognizing social dominance
Priority of access
Supplant / seize
Formal signal of subordinacy
Pant-grunt / bow
Female-F relationships: Feeding competition key?
 Little fighting, but ~80% fights over food
 Residents aggressive to immigrants
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Immigrants avoid dominant female
Immigrants choose less dense neighborhood
Few range switches after settling
Range switches costly
Potential infanticide by females
All Males Dominate all females
o Young males fight more when females fight back
 Male-Male relationships: dominance = key
Intercommunity Relations
Patrols and raids
Violence
More males = more intergroup violence
Winners of intergroup encounters gain territory which leads to shorter IBIs
(increased female core area) and increased body mass.
What are the gains of intergroup violence?
Exclude outside competitors for mates
Maximize food for themselves and their mates and offspring
Maximize female reproductive rates
Fission-fusion creates a low cost of killing
Lecture 2: Intergroup relations and Baboons/ Mangabeys
Home range: Area exploited by a group of primates (defended but not exclusively) –
overlap
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.
Territory: Area exploited and EXCLUSIVELY defended by primates – no overlap
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 (?).
Characteristics:
• 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
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.).
• Problem of how to define an intergroup encounter – very different
depending on species and habitat.
• 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.
• 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.
• 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.
• 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.
• Why Defend a territory?
• 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)
• Size of core area vs distance traveled per day
• Index of defensibility: r/d
• R= Average day range (path length)
• Core area or home range diameter
• ID <1 = not territorial
• ID > 1 = territorial (generally)
Baboons and Mangabeys
• Share a recent common ancestor
• Part of the Afro-papionins :
• savannah baboon, drill and mandrill, gelada, and hamadryas,
mangabeys
• Baboon social organization
• Stable troops
• >10 females
• > 5 males
Savanna baboon social structure
o F-F: Strong alliances, dominance
o F-M: Friendships (increases F reproductive rate)
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M-M: Dominance, some coalitions
Intergroup: Xenophobia +/- territoriality
Female-female dominance = stable, based on mother’s birth rank
Agonistic relationships among females have few reversals.
High-ranking (female) baboons eat more
Females care about rank reversals between more than within
families
o Female dominance hierarchies don’t always predict success
 But: sociality can be more important than rank (in
promoting RS)
 Grooming time is a measure of friendship.
 But, it also responds to interest of infants.
Female-male friendships:
Defining ‘Friendship’ between Female and Male.
• Spatial proximity. Use ethograms to score dyads (range 0-20). For
most FF, top M scores ‘10’; the rest scores <3.
• Grooming. Record all grooming bouts. For average F, top M = 65%
of her grooming.
• Defining a ‘Friend’. ‘Friend’ = high score on BOTH proximity &
grooming.
• (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 !
Intergroup relationships: Xenophobia +/- territoriality
Lecture 3: Lemuriformes and Life History
Brain Life History
 Neocortex – Responsible for cognitive abilities (i.e. Reasoning, Conciousness,
etc.)… makes up most of the brain in primates.
 Although brain is small in size, it requires a lot of energy from the body.
 Ratio of Neocortex to Medulla – humans and primates ratios are considerably
larger than other animals… intelligence factor?
 EQ (encephalization quotient) – ratio of brain size vs. body size… primates larger
than expected.
 Larger brained mammals play more… true for relationship between mammals,
not within orders (like within primates).
 Executive Brain Ratio – (neocortex and striatum)/(brain stem)…
1) behavioral innovation
2) social learning
3) tool-use
 Social Brain Hypothesis: relationship of size of neocortex and size of social
group… the ability to maintain social relationships was the primary selective
factor in the evolution of large brained primates… not because of faster brain
growth, but rather reduced body growth.
 Larger species:
- larger brain size ratio
- longer gestation
- fewer infants
- larger infants
- longer weaning ages
- delayed sexual maturity?
- Slower reproduction
*THIS IS PROBABLY IMPORTANT (just a suggestion)
 Delayed maturation in primates… here’s the trend:
mammals<primates<apes<humans (maturation onset)
 Humans and primates have adolescent growth spurts, whereas other mammals’
growth curve decreases in rate from birth.
Lemuriformes
 Madagascar (~50 mya)
 When humans came (~1500 ya), 1/3 of lemurs disappeared
 Little sexual dimorphism in body weight
 When living in groups, females dominate males.
 Dwarf Lemur – smallest primate ~30g
 Sexual Dichromatism – the condition in which males and females of a species
differ in body color.
 Lemur Catta (Ring-tailed lemur) are the most widely studied… (the lecture slides
list all sorts of lemurs… look at them if you want but I don’t think it’ll be that
important b/c its way too specific)
 Lemur Catta –
- Diurnal
- Multi-m/Multi-f
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Female philopatry and nepotistic hierarchies (single matriline)
Frequent aggression and promiscuous mating
Higher-ranking males have higher RS
Higher-ranking females produce more cortisol = more stressssssss
Brief (2-4 days) mating season
NO m-f friendships
-I tried to make it simple in a nutshell… while I was sipping on some nice red wine to
take the misery out of 3 finals in 3 days… I love all of you… that’s the booze talking.
Peaceloveandhappiness.
Lecture 4: Phylogeny of Behavior and Sakis/Uakaris/Titis
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Within group contest = WGC
Within group scramble = WGS
Between group scramble = BGS
Between group contest = BGC
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Scramble—entire group equally affected, resources not economically defensible,
NO fighting
Contest—Winners do better than losers, resources economically defendible,
fighting and dominance help
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(# of males)(IBI)_____
Operational Sex Ratio = (#females)(#breeding days/birth)
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OSR measures importance of male fighting ability
o Higher OSR more aggressive
o Higher OSR higher sexual dimorphism
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Increased sexual dimorphism in body weight with increase in mass ex:gorillas
Increased sexual dimorphism in body weight with increase in number of females
per male. ex: one-male groups versus monogamy
o Same is true for canine dimorphism
Chapter 8: Sakis, Uakaris, and Titi Monkeys
Titi Monkeys (Callicebus)
 Located in western and southern Amazon Basin, as well as a disjunct
distribution between the Atlantic coastal forests of Southern Brazil
 Distinguished by pelage color mostly
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Certain groups tolerant of habitat disturbance by humans and seasonal
flooding
Form small, cohesive, pair-bonded groups… in many ways represent the
‘classic monogamous’ pattern
Sexually monomorphic in body size and color
Bearded Sakis (Chiropotes) and Uakaris (Cacajao)
 Form large, more loosely structured groups that may fission into smaller
feeding parties
 Males do not take an active part in infant care and little sexual dimorphism
in body mass.
 Large/Long home ranges
Bearded Sakis
 Present in upland, nonflooded eastern Amazonia… absent from western
Guyana
Uakaris
 Range widely
 Particularly inhabit areas that flood seasonally along white-water rivers
and black-water rivers (a study where only uakaris traveled everywhere in
a reserve… even through a deeply flooded forest… those crazy fuckers)
 Rivers in these areas have selected for fast-growing stems that allow
young plants to reach great heights quickly
Sakis (Pithecia)
 Two groups: A Guianan group and an Amazonian group
 Guianan Sakis (white-faced and pale-faced) strongly sexually dichromatic
 Males: black w/ white face
 Females: gray-brown w/ striped face (All females similar)
 An “intermediate” between titis and bearded sakis/uakaris
 Group size: small, and many (not all) conform to the ‘two-adult group.’
Physical Characteristics of the Pitheciines
 All sakis have bushy tails (‘Tail-wagging)
 Long: Sakis and Bearded Sakis
 Short: Uakaris
 Titis are the smallest-bodied (Adult females heavier than males)
 Similarities in dental anatomy unite the sakis/uakaris and separate them
from the titis  titis lack the incisor/canine complex
 Dental adaptations in sakis/uakaris infer high incidence of seed
predation… are able to open mechanically protected (i.e. hard or thickcrusted) fruit
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Bearded Sakis and Uakaris use:
1) Uneven surface of tooth for positioning
2) Hunter-Schreger bands  resist cracking of teeth
*Titis don’t have these*
Feeding Ecology and Diet
 Titis: Fleshy fruits… do not appear to ingest a high proportion of seeds
 Sakis/Uakaris: Seeds make up 1/3 of the diet (sometimes more than 2/3)
Leaves, flowers, insects, bark, pith, termite nests, and wasp
nests are secondary resources  provide and intermittent
nutritional boost to the white-faced saki diet (specialize in
things with high protein)
*Major advantage of a ‘seed intense’ diet is the ability to
reduce the impact of seasonal fruit shortages* (They do eat
fruit in wet-season… aka… when they can)
 One species of Uakaris have been known to accumulate fat tissues when
fruit shortages are low or about to be low (similar to the way ring-tailed
lemurs and other lemurs do in their tails)
Group Size, Use of Space, and Intergroup Relations
 Titis and Pithecia Sakis: small, territorial groups
 Use of calls to exhibit territoriality and “proximity-dependent avoidance
 Bearded Sakis and Uakaris: large, far ranging as any platyrrhine
 Bearded Sakis fission slightly when in a large area of multiple feeding
trees, but travel cohesively between sites
 Strong, positive correlation between group size and day-range
Reproduction and Development
 Sakis: 5 month gestation and 30 month IBI
 Titis: approx. 4 month gestation and 11.8 month IBI
 Male caretaking peaks in second month and continues until the
sixth month
 Both sons and daughters disperse… daughters disperse earlier
than sons… b/c of high juvenile mortality, parents benefit from
retaining subadults who provide “critical aid” to siblings
 Whereas White-faced Sakis (Pith.) become self-locomoting early, Bearded
Sakis and Uakaris are carried until 9th Month.
Summary:
 Vertical clinging and leaping of White-faced Sakis makes it easy for them
to move through low-to-middle canopy levels compared with the
Amazonian Sakis
 Titis contrast with the other three pitheciines in aspects of feeding
 Bearded Sakis are found more often in nonflooded forests
 Uakaris use flooded habitats extensively
Lecture 5: Evolutionary History
Primates arose 65 mya- new niches, adaptive radiation
5 mya- Pliocene Era, global cooling continued, Theropithecus baboons
widespread in Africa
1.8 mya- Pleistocene- Theropithecus replaced by Papio
Hamadryas- live in dry habitat, Arabia, NE Africa.
25% smaller than Savanna Baboons, great sexual dimorphism
fertile hybrids with Anubis baboons
Social Grouping: Troop- 600 (sleeping group- predation protection)
Band- 30-100 (largest social unit, may travel together or disperse,
no MM fighting within bands)
Clan- 10-20 (little MF dispersal, may forage independently)
Family (OMU)- 2-10- (Prime dominate M, leader of F)
High ranking mothers are permissive parents, F coalitions only with M- remember
the “double signal” where F presents to M while threatening another F
MM respect within clan (remember cage experiments – knowing MF bond) , young M
courts young F
Hamadryas M herding of F and F following= strong MF bond (experiments with Anubis
F who don’t follow, M who don’t respect bonds)- F has to “like” her male
Compared to Anubis- Hamadryas show less fighting, no dispersal, more sexual
consorting
Lecture 6: Primate Diversity and Lorisoformes/Aotinae
(Lemurs)
They got to Madagascar from Africa by rafting- floating on large clumps of vegetationstarting 80 mya
Lemurs have many morphologically primitive features, including a “wet nose”- a
primitive mammalian trait- they have a very good sense of smell and use scent marking,
esp during mating season.
Lemurs have a grooming claw.
Small lemurs such as mouse and dwarf lemurs are often branch runners, larger
sportive lemurs are vertical leapers.
Female dominance is found in the majority of lemur species- FF aggression, low sexual
dimorphism, seasonal breeding, high infant mortality and cathemerality (both nocturnal
and diurnal activity peaks)
Why such characteristics1. Energy Conservation Hypothesis- Madagascars extreme climate + high cost of
reproduction resulted in female dominance- in group living lemurs, all the females
are pregnant/lactating simulataneously- high FF feeding competition- female
dominance for first access to food resources. Low Basal Metabolic Rate (BMR)
small group size, torpor, and seasonal breeding also might supports the energy
conservation hypothesis
2. Evolutionary disequilibrium hypothesis- recent extinctions allowed lemurs to
switch from nocturnal to diurnal. – female dominance might be a relic of old
monogamous nocturnal pair bonded social systems.
Nocturnal Lemur Social Systems (3 types): gregarious pairs- cohesive groups (Aotus);
dispersed (Mirza- multimale)- solitary foragers with social networks, (Phaner dispersed
pairs); solitary- completely solitary.
Nocturnal Primates are very diverse, many many species (25% of primates), still
relatively very little is known about them.
Lecture 7: Reproductive Endocrinology and Molecular
Primatology
Reproductive Endocrinology:
 Biology of reproduction:
o Primary bioactive sex steroids:
 Estrogen
 Progesterone
 Testosterone
 All 3 are detectable in all mammals through noninvasive (fecal)
techniques
o Cortisol = stress
o HORMONES are important because they measure timing of:
 Ovuation
 Conception
 Early pregnancy (which could terminate early on)
o Techniques:
 URINE is good because it’s noninvasive, constantly produced, and
shows metabolism activity
 FECES are good because they’re noninvasive, constantly
produced, and don’t have to be frozen like urine. AND they give
you DNA. BUT it’s risky bacteria-wise. USE GLOVES.
 SALIVA is collected by making primates chew on ropes and then
centrifuging them. Kinda invasive…
 BLOOD collecting is stressful in trying to capture the primates
and led to possible behavioral abnormalities. That was abandoned
in labs, and you couldn’t EVER do it in the field.
MOLECULAR PRIMATOLOGY= molecular variation between species
 Molecular primatology is good because it’s easier and MUCH less ambiguous to
assess molecular states than morphological ones.
 Leads to knowledge of:
o Kin relationships between groups
o inbreeding= important because it determines pop. Health.
^ inbreeding = lower health
o Human health and disease
o Rate of change of genes
o Phylogeny ie common ancestors
o It could help with CONSERVATION and we all know how important that
is…
 Testosterone increases your ability to fight.
o Testosterone study showed male chimps are much more aggressive when
parous females are swollen. 40% more so than when nulliparous females
are swollen, and 25% more than when nobody was. Or something like
that. Basically it’s higher.
o Wild bonobos have higher testosterone as correlated with higher
dominance rank, but there’s no relationship in captive ones. BETTER
FED MONKEYS DON’T COMPETE AS MUCH!
 Ketone studies-> the more ketones, the more severe your metabolic derangement.
Starvation.
 Upon male takeover, Chacma baboons showed higher stress (cortisol) in females
that DIDN’T have a male friend than females who DID.
Lecture 8: Sexual Selection and Gibbons
From Book, Overview of Gibbons:
 Hylobatidae, twelve species, four taxa.
(Temporal split between subgenera might be as big as between humans and
chimps, but as of right now are still being classified under the same genus level.
*lumpers vs. splitter debate*)
 Rain forests of eastern and southeastern Asia.
Borneo, northern Sumatra, malay peninsula, Thailand, all over Indonesia
 “Lesser apes.” Far smaller than other hominoids, hence the term.
Names given below just for sake of recognition:
o Taxa: Hoolock, nomascus, hylobats, and symphalangus
o Some specific species: Siamang, lar gibbon, agile gibbon, pileated gibbon
 Small arboreal ape: They don’t come to the forest floor often, but move quickly
through the trees, using a unique “pendulum-like swing.” Extremely long
forearms, mobile shoulder, hook-like hands.
 Ischial tuberosities: a bony structure described in the book as a “callus-like
sitting pad”
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Frugivorous: “fig exploiters”; about a quarter diet comes from figs alone, another
significant portion from other ripe fruit; leaves account for 31% of diet; remainder
is young leaves, flowers, and insects. Seem to select small fruit more often than
other ape species, although in general they still prefer larger fruit.
Relevant to Sexual Selection:
“Gibbons establish monogamous, egalitarian relations, and one couple will maintain a
territory to the exclusion of other pairs.” –book by Frans de Waal.
 Low sexual dimorphism.
 Territorial: small, well-defended territories. Group sizes of 7-10.
 Stable Pairbond: two adults, one to three offspring.
o Five age-grades:
 1) infant (0-1yrs)
 2) juvenile (2-5yrs)
 3) adolescent (5-8yrs) *sexual maturity, but dispersal delayed
 4) subadult (8+yrs)
 5) adult (mated with territory)
o (In wild), Females give birth after gestation of 7mo. Single young. 6-9 yrs
old when they first give birth. 2-4yr birth interval.
 Regular vocal displays or songs.
o Broad variety of loud calls can be heard over long distances. Significant
genetic component to the song.
o “solos” versus “duets”:
 mated males sing solos frequently before dawn
 Duets, on the other hand, are comprised of 1) introductory
sequence, 2) female great call, 3) males reply or coda. Mostly sung
in the morning and can last up to 30min.
From My Notes:
Fisher’s runaway sexual selection: females choose an arbitrary trait as being attractive,
and so the trait gets more and more exaggerated. For example, female whales
systematically choose the largest male; there’s nothing the males can do. Or in the case of
sexual swellings, the brightest sexual swelling is most frequently chosen.
Lactational amenorrhea: as long as the female feeds her baby, she won’t get pregnant.
Partly explains why the females can’t get pregnant so quickly after having their baby.
Intrasexual selection = competition for mates. “depends on the advantage which certain
individuals have over other individuals of the same sex and species, in exclusive relation
to reproduction.
Intersexual selection = choice of mates
More females you have for one male, the more important sexual dimorphism.
i.e. For humans? We’re monogamous, so we’re pretty monomorphic, (exact same
canines), but heights and weights are skewed toward guys
Sexual selection and testes size: 86% of the variation in (testes
mass)-to-(body mass) is explained by a direct proportional
relationship; in general, larger the testes, larger the body mass.
Scramble competition: a male’s reproductive success is based not on the ability to
fertilize a single highly-reproductive female, but on the ability to mate with as many
females as possible each mating season. Hence the advantages of larger testes and
stronger sperm. Applies in particular to mm-mf societies.
Trends:
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Monogamous species: generally have smaller testes than expected. (i.e. once pairbonded, they’re set for life, so no need to compete as much.)
Polygynous species: smaller testes (so, there’s like four males fighting for twenty
females, and at each mating season, the ladies are up for grabs.)
Multi-male-multi-female societies: very large testes (scramble, as described above)
Sperm count versus volume: The higher the frequency of your ejaculate, the smaller
the volume and sperm count; the lower the frequency, the more volume and higher
sperm count.
The three factors of dimorphism:
1) Body mass, 2) canine height, 3) testes mass
 Monogamy (1 male : 1female)
 Polygyny (1 male: many females)
 Polyandry (1 female: many males)
 MM-FF (many females: many males)
(Polygamy)
Sexual swellings:
There is no society of polygynous primate species where you find sexual swellings, but in
mm-ff, females usually have swellings. Why? Because females would want to advertise
here to get as many males as possible to mate with her. Creates paternity uncertainty, one
way of preventing infanticide.
Why have human women lost sexual swellings?
1. Monogamy. Hypothetically speaking, protection against infanticide is
unnecessary.
2. There is variation as to when exactly ovulation occurs.
Note that these are competing strategies; On one hand, the swellings serve to increase
paternity certainty (because the male ‘knows’ when she is in estrous), and on the other
hand, they serve to confuse paternity…I’m kind of confused here, sorry.
Are there “False” sexual swellings?
Yes, in langurs, where males will take over a group and commit infanticide.
Possible explanation for monogamy in gibbons:
Conflict between mate-guarding and range-defense?
Maybe leaving the female to her own devices is too costly to be able to protect the
territory well; perhaps males are simply defending their territory, and in the process guard
their mates because that is where the female happens to be.
Few cases of infanticide in monogamous societies; maybe monogamy mainly serves to
protect the children.
Just for fun: the group survey we took in class:
Girls top criteria for guys?
1. Money
2. Height
3. Status
4. Looks
5. Confidence
6. Has to make a strong aggressive move
Guys for girls:
7. Looks
8. Being able to hold a conversation
9. Intelligence
10. (Alain: “would you date a taller, older girl?”)
Lecture 10: Food, Social Relations and Squirrel Monkeys

Squirrel monkey basic facts
o Genus: Saimiri, 5 species
o Geographic distribution: Northern part of South America
o Social organization: flexible (fission-fusion?) groups, quite large (up to 50)
o Social dominance: F > M, except during mating season when M hierarchy
forms
o Mating: seasonal, with fattened males
o Feeding
 Truly arboreal
 Fruits, arthropods & small vertebrates
o Predation
 Big groups  high susceptibility
 Kinds of predators: aerial & terrestrial hunters, parasites (e.g. malaria)
 Defense strategies/adaptations
 Huddling
 High vigilance, alarm calls (different types)
 Mobbing raptors
 Birth seasonality to swamp predators

What determines the presence and sex of philopatry?
o Model 1: intergroup competition model (Wrangham 1980)
o Model 2: predation/intragroup competition model (Van Schaik 1989, Sterck et al
1997)
o Condensed diagram (Model 2 + food distribution box, which is from Model
1):


BGC = between group competition, WGC = within group competition
When does it pay to form coalitions?
o To defend large clumps of food against other groups (Wrangham 1980)
 Pro: does happen; could have long-term effects
 Con: BGC looks less important than WGC
o To defend smaller clumps of food against other group members (van Schaik 1989)
 Pro: does happen; Saimiri fits

o
o
o
o

Con: assumes negligible BGC, when WGC and BGC can co-occur
(e.g. vervets, red-tailed monkeys)
To compete for safety when there is predation (van Schaik 1989)
 Pro: baboons/cebus, HR females in center of troop
 Con: hamadryas don’t fit (no FF coalitions to be near M)
Economically defensible territory (not in literature)
 Pro: happens without WGC or large patches
 Con: conditions unspecified
(Diurnal) terrestrial locomotion (not in literature)
 Pro: cercopithecines: terrestrial  alliances
 Con: Lemur catta (no within-group alliances)
Dominance contests (not in literature)
 Pro: alliances critical for high rank (e.g. Macaca)
 Con: S. sciureus (no FF coalitions!)
Competition/coalition/philopatry models applied to Squirrel monkeys
S. boliviensis (Peru)
Aggression
FF coalitions
Food
distribution
Philopatry

.29
Common
Large, dense fruit
patches
Female
S. oerstedii (Costa
Rica)
.004
Rare
Small, not dense fruit
patches
Mostly male
S. sciureus (Suriname)
1.50
Rare
Very small, dense fruit
patches
Male?
Why do females stay with kin?
Within group coalitions pay over food or safety
Between
group
coalitions
pay over
food
+
-
Resident – Nepotistic
Resident - Egalitarian
Resident – Nepotistic
Dispersal – Egalitarian
+
S. boliviensis (Peru)
-
OR
Resident – Individualistic
S. oerstedii (Costa Rica)
S. sciureus (Suriname)
Lecture 11: Feeding & Grouping/Social Relationships and
Orangutans

Preferred foods






o Reproduction: chimp FF tend to conceive when they are eating the greatest %
of fruit
o When these foods are abundant, primates diets are very similar (they all eat
these)
Fallback foods = pith, leaves (THV = terrestrial herbal vegetation)
o Eaten when preferred foods are unavailable
o When food is scarce, primate diets diverge (they specialize on different
fallback foods), as you can see below (each line represents a different primate
species):
Effect of difference in fallback foods: chimpanzees need fruit whereas gorillas can
survive with just foliage. This difference in diet has several effects on competition
and grouping:
o Feeding competition is intense in chimps but relaxed in gorillas
o Intragroup competition is intense in chimps and virtually nonexistent in
gorillas
o Chimp groups are unstable whereas gorilla groups are stable
o Party size in chimps is smaller when food is poor, gorilla party size is stable
o Chimps do not form M-F bonds, while gorillas form strong M-F bonds
Frugivory and scramble competition
o Bigger groups  more competitors (scramble competition)  all must travel
further (longer day-ranges)  cost for all
o RRC = relative ranging cost = (daily-path-length of group / group size) / (day
range of lone individual) (the important thing is to understand conceptually
that it is a measure of the increased ranging cost of one additional group
member, I think)
Relationship b/t group size and day range varies b/t species, is less/none in folivores
Food and contest competition
o The upper crown of a tree is better (more fruit), groups/individuals prefer it
o Dominant primates (studies on chimps & 3 monkey species) feed higher up on
tree
Orangutans
o Geography: Asia (1 species in Sumatra & 1 species in Borneo)
o Conservation: no more orangs in Suaq Balimbing, which sucks b/c they were
social
o Social system
 Solitary
 No infanticide
 Build nests
o Dimorphic males:
RS
Choice of FF
Ranging patters
Size
Throat pouch
Musky odor
Hair length
Rank
Aggression twd FF
T levels
Day range
Long calls
Copulation rate
Forced copulations
Flanged
high
Prefer fecund
Both resident and transient
≈ 86 kg
Yes
Yes
Long
Dominant
No
High
Short
Yes
Less
5.3 %
Small
Lower, but still father offspring
Prefer fecund
Both resident and transient
≈ 40 kg
No
No
Short
Subordinate
Yes (forced copulations)
Low
Longer
No
More
88.2 % !! (mostly out of
consortship)
o Mating system: FF mate w/ several MM, no long-term bonds. Copulations are
infrequent, but long (3-29 min).
o Diet
 Frugivores
 Fruit mast unpredictable, so they are in a negative energy balance
during many months of the year
 No sustaining fallback food
 Competition intense
o Why are they solitary? (van Schaik & van Hooff 1996)
 Ecology: predation unimportant + high within-group scramble
competition (especially for mother and big males)  no benefits of
bonding
 Evidence: when fruit is abundant or when they are provisioned they
are social
Glossary
Birth Seasonality: this term refers to the synchronous timing of births in a population of primates. One
explanation for the presence of an annual peak in the number of births is that high numbers of infants
“swamp” predators (they can’t prey on that many!), so more infants survive than if a few infants were
born every month.
Philopatry: this term literally means “home loving.” It refers to an animal’s “decision” to stay in its
natal group. To avoid inbreeding, usually one sex leaves while the other one stays or both sexes
migrate. Female philopatry occurs when females stay in their natal groups. Male philopatry occurs
when males stay in their natal group.
BGC: between group competition. This refers to competition that occurs between one group of
primates and another group. It is usually over the use of territory and food patches.
WGC: within group competition. This refers to competition between members of the same group. It
may be over food, safety, or mates. This term is closely connected with the idea of hierarchies and
coaltions.
Nepotistic: this refers to a social structure where competition for rank occurs via allies, usually kin.
The opposite of a nepotistic social structure is an individualistic structure
Individualistic: this refers to a social structure where there are no alliances in rank competition. The
opposite of an individualistic social structure is a nepotistic structure.
Egalitarian: this refers to a social structure where dominance relations are weak or not present. The
opposite of this structure is a despotic structure, where there are clear & linear hierarchies.
Preferred foods: these are the foods that primates prefer and will eat first whenever they are available.
For a lot of primates, fruits are the preferred foods.
Fallback foods: when the preferred food is not available, primates will eat fallback foods to sustain
themselves. These are usually piths and leaves, known as THV (terrestrial herbal vegetation).
Frugivore: an animal that feeds primarily or exclusively on fruit. This method of feeding can be more
efficient than consuming the vegetative portions of a plant, due to higher concentrations of sugars,
vitamins or proteins that many plants put into fruit.
Folivore: an animal that specializes in eating leaves. Mature leaves contain a high proportion of hardto-digest cellulose and relatively little energy. For this reason folivorous mammals tend to have long
digestive tracts and slow metabolisms.
RRC: relative ranging cost. This is a measure of the added cost, in terms of distance traveled per day,
of having an additional group member.
Fruit Masting: masting is a group phenomenon that results when plants within a population correlate
their fruit production both in time and in size of crop. It is thought that masting occurs as an
evolutionarily stable strategy enabling plants to exert some influence over the size of animal
populations that predate on the fruit.
Energy Balance: energy intake – energy expenditure. When you intake more than you expend, you are
in a positive enero gy balance. When you expend more than you intake, you are in a negative energy
balance.
Chapter 7: The Cebines
Toward an Explanation of Variable Social Structure


Cebinae is a subfamily of New World Monkeys (platyrrhines) made up of capuchins
(genus Cebus) and squirrel monkeys (genus Saimiri).
Sympatry is common and mixed-species associations form between the two genera






Feeding
o Considered the most omnivorous of NWM (fruits, insects, etc.)
o 75% of active day enganged in foraging
o Cebus: extractive foragers, good at accessing protected foods
Predation
o Raptors, felids, snakes, coyotes
o Squirrel monkeys more vulnerable than capuchins because they are way
smaller
o Adaptations : bigger group size in Saimiri, contact calls as “security blankets,”
mixed-species associations which are generally maintained by Saimiri
Reproductive & growth parameters
o Saimiri are strict seasonal breeders (2 months of mating), Cebus not as strict
o Slow maturation rates and long life spans in Cebus
o No external signs of ovulation or pregnancy
Group structure: both form mixed-sex groups, much diversity in size and composition
Mating systems
o Cebus exhibit elaborate mating rituals prior to mating (see p. 115 for
description), and alpha males sire the majority (but not all) of infants born
o Saimiri males fatten up during breeding season (deposition of wate b/t skin &
muscle), correlates to levels of testosterone, larger males selectively preferred
Dispersal patterns & social structure
o Cebus: F philopatry and M dispersal. FF bond and are resident-nepotistic.
Though MM are generally dominant over individual FF, the alpha F ranks just
below the alpha M and FF form coalitions, so in the end it’s a rather
egalitarian society. Social grooming and proximity help maintain cohesion
and friendships
o Saimiri: dispersal varies with geography. Grooming is almost completely
absent.
 S. oerstedii (Costa Rica) exhibits flexible M philopatry, M bonds, and
weak to no F bonds. Intersexual relations are egalitarian.
 S. boliviensis (Peru) display F philopatry, matrilines, F dominance
 S. sciureus (Suriname): both sexes disperse, M dominant, stable
hierarchies in both sexes, high intragroup aggression
o Ecological explanations for grouping variability in Saimiri
 Costa Rica: food patches not cannot be monopolized by individual or
group  no advantages to F bonding  F dispersal (to not compete
directly w/ kin)
 Peru: food patches monopolizable by groups  F bonding  F
philopatry
 Suriname: food patches monopolizable by individuals  strong
contest competition  F disperse (to not compete directly w/kin)
Chapter 17: Orangutans in Perspective
Forced Copulations and Female Mating Resistance
Geography & Habitat: Borneo & Sumatra, wet rain forests, peat and freshwater swamps, lowland
forests
Taxonomy: recent analysis recognizes two species, one in Borneo (3 subspecies) and one in
Sumatra
Morphology
 The red ape: covered with thick, reddish-orange hair
 Adaptations for arboreality
o Quadrumanual clambering: the grasping of supports with both hands and feet
o Relatively long arms, hands and feet
o Shallow hip joint that allows legs to extend over 90 degrees
 Males
o Indeterminate growth (can grow and put on weight throughout life)
o Flanged male
 > 80 kg
 Flanges = cheek pads
 Pendulous throat pouch
 Long hair
 Musky odor
 Long calls = loud vocalizations
o Unflanged male (used to be called “subadult” but that is a misnomer)
 Half the size
 No secondary sexual characteristics
 No long calls
o Unflanged male endocrinology: gonadotropin and testicular steroid levels enough for
spermatogenesis but insufficient for secondary sexual maturation
 Females: 45% of male body size  extreme sexual dimorphism
Food Availability: food resources are patchily distributed in space and time. Mast fruiting
(synchronous fruiting of plants on an unpredictable cue to swap out seed predators) occurs every
2-10 years
Diet and Nutrition Consumption
 Preferred: fruit
 Fallback foods: leaves, bark, pithy vegetation, insects (esp. termites), and very rarely
vertebrate meat
 Physiological adaptation for fat storage
Activity Patterns: Solitary foragers  coping strategy for lower food availability
Ranging and Philopatry: large ranges, not territorial (ranges too large to be defensible), F
philopatry
Social Relationships
 Male long calls are important vehicles of communication in dispersed orangutan society
 One flanged male can typically be recognized as dominant
 Key: F  female, M  flanged male, m  unflanged male
o M-M: intolerant, hierarchical
o M-m: M dominates m, M more tolerant toward m than toward other Ms
o
o
m-m: tolerant, potentially hierarchical
F-F: potentially hierarchical
Tool Use and Culture: tool use relatively rare, but present, such as leaf umbrellas, leaves for selfcleansing, leaves as drinking vessels, scratching sticks, dead wood fruit-openers.Local differences
(culture) exist. At Suaq Balimbing, high density of individuals may permit more cultural
transmission .
Reproductive Parameters
 Male development
o Flanging highly variable, from immediately after adolescence to >20 years unflanged
o Unflanged  flanged transition quite rapid, < 1 year, mediated by surge in testicular
steroids and growth hormone
o Two hypotheses to explain arrested development
 Presence of flanged MM suppresses unflanged M development (via long
calls, connection between auditory brain regions and hypothalamus??)
 Alternative reproductive strategy: “play it safe”
 Female development
o IBI: 8-9 years!! (why? Periods of negative energy balance + lactation  ovarian
suppression)
o No sexual swellings, concealed ovulation  males rely on F proceptive behavior
Mating Behavior
 Face-to-face, 10 minute long copulations
 Flanged male strategy: “consort/combat”
 Unflanged (or subordinate flanged) male strategy: forced copulations
 Females strongly prefer and are proceptive toward dominant male
 Do flanged males out-reproduce unflanged ones? Results inconclusive
Forced Copulations: Sexual Coercion or Mate Assessment?
 Sexual coercion hypothesis: F resist solicitations of unflanged and flanged subordinate males
because these males are not preferred
 Mate assessment hypothesis: F resist in order to gain information about the health/vigor of
males, and thus select for good genes
 Evidence: one study found that females are consistent in their resistance to certain males,
even when these males had already mated with them in the past, supporting the 1st hypothesis
Female Choice: Infanticide Avoidance, Good Genes or Both?
Fs mate with dominant Ms:
During stable times, Fs resist
nondominant Ms:
During unstable times, Fs
should mate polyandrously,
esp. with potential up-andcoming Ms:
Infanticide Avoidance
For infanticide protection
To concentrate paternity
into the dominant M &
assure their protection
To confuse paternity and
avoid infanticide if takeover occurs
Good Genes
For good genes
When chance of insemination
is high, to avoid conception by
low-quality males
To obtain these males’ superior
genes
How does dominant M
know if F mates with
Dominant males not always
fathers (one paternity test
Problems
others?
No infanticides observed to
date
results)
Why do non-reproductive Fs
mate polyandrously during
unstable times?
Chapter 28: The New Era of Primate Socioecology
Ecology and Intersexual Conflict



This chapter reviews the existing socioecological models of primate behavior, discussing
their limitations and proposing new avenues of research.
Important models discussed
o Wrangham 1980s:
 Background assumption: food is the primary limiting factor for F RS and
number of mates in the primary limiting factor for M RS
 The defendability of food resources against other groups determines the
degree of female bonding, which in turn determines female dispersal patters.
o Schaik and van Hoof 1983: the lower limit to group size is set by predation pressure,
while the upper limit is influenced by the degree of feeding competition
o Isbell 1991: food abundance shapes between group relationships, while food
distribution (clumped versus dispersed) shapes within-group relationships
o Sterck et al. 1997: there are four grouping categories based on the degree of within
and between group competition, which can be strong or weak.
 Dispersal-egalitarian
 Resident-egalitarian
 Resident-nepotistic (but also despotic)
 Resident-nepotristic-tolerant
o Isbell 2004: “dispersal/foraging model”
 Explores how the locational (travel to unfamiliar home range) and social
(harassment) costs of dispersal influence formation of kin groups.
o Foraging efficiency remains the main selection pressure, but success in intergroup
competition is no longer the main benefit of living with kin
o Freeland 1976:
 Assumption: group size, population density, and number of mating partners
are likely to increase disease transmission
 Primate sociality can be explained as an adaptation that minimizes risk of
acquiring new pathogens and limits the pathogenicity of diseases already
harbored, thereby maximizing individuals’ reproductive fitness.
o Infanticide controversy
 Many primatologists argue that infanticide or sexual coercion exert a strong
selection pressure on behavior & social structure
 This is a big controversy however, with some arguing that infanticide is an
adaptive strategy with a counterstrategy (infanticide avoidance) while others
arguing that it is not
o Sussman et al. 2005: cooperative and affiliative behaviors are equally likely to
influence sociality (than competition) given the higher proportion of time primates
devote to these behaviors
Some terms/ideas
o Contest/interference competition versus scramble competition (first-come-firstserved)
o Intergroup versus intragroup competition
o
Grouping dimensions
 Egalitarian versus despotic (hierarchical)
 Individualistic versus nepotistic
 Tolerant verus intolerant
Chapter 29: Primate Nutritional Ecology
Feeding Biology and Diet at Ecological and Evolutionary Scales




Introduction
o Proximate scale (how): measures the short-term responses of an individual to
immediate circumstances (e.g. food availability  group size / day-range)
o Ultimate scale (why): if an animal’s response has a heritable component and is
under selective pressure, it can become an evolved adaptation, considered by
this scale.
Feeding categories: herbivores, carnivores, omnivores  but chapter argues these
categories are confusing and often artificial, masking dietary variability, etc.
Nutritional requirements
o Macronutrients
 Carbohydrates: major source of energy. There are simpler ones and
more complex ones, the best being the ones that are easier to digest
(glucose, fructose). Digestion of complex carbohydrates requires
enzymes. Some carbohydrates (like cellulose) even require bacterial
symbiosis (fermentation). Sources: fruit pulp, also vegetative plant
parts lie leaves & bark
 Protein: provide energy and are critical for growth, reproduction and
tissue replacement. Requirements are generally low, so deficiency is
prob. not a big issue. Sources: leaves, insects, other animal matter.
Immature leaves have more protein than mature leaves (think: they are
growing).
 Lipids: highly concentrated source of energy. Sources: insects, other
animal matter, seeds. Influence reproductive hormones, so insufficient
intake my result in reproductive suppression.
o Micronutrients
 Minerals: inorganic elements that serve as structural components of
molecules (e.g. iron in hemoglobin), activators of hormonal/enzymatic
processes, regulators of cell activity and components of body fluids.
Sources: foliar material, then bark, then fruit.
 Geophagy: soil consumption, quite common as a mineral
supplement
 Vitamins: facilitate use of energy. Sources: all except B12 can be
derived from plants (B12 from microbial activity in gut & animal
resources)
o Water
Metabolism and energy, or what is a “quality” diet?
o What determines how much energy a primate requires

Dietary thermogenesis (energy required to process, absorb and store
nutrients)
 Basal metabolism
 Growth & reproduction
 Activities (traveling, foraging, social interactions, predator avoidance,
etc.)
o Metabolism = all the chemical re actions of the body
 Anabolic processes = synthetic, require energy
 Catabolic processes = degradative, release energy
o Dietary quality = how capable a food item / diet is to yield energy
o A question of size
 Small mammals require relatively more energy than large mammals
 Small mammals must eat high-quality foods, but b/c of size need less
of it
 Large mammals can eat worse quality food (longer time in digestive
track) but more of it. They can also eat high quality food, of course
 Ecological challenges
o Leaves are more abundant and predictably available, fruits are highly
unpredictable
o Responses to challenges
 Modulation of group size (as explained in lecture 10)
 Morphological adaptations, for example cheek pouches
 Dietary flexibility (requires certain digestive track features &
strategies)
 Chemical challenges
o Plants & insects arm themselves with “secondary metabolites” of two kinds:
 Digestion inhibitors, e.g tannins, which bind with proteins to form
insoluble complexes
 Toxins, like alkaloids and cyanogenic glycosides
o Primates strike back
 Surfactant substances found in gut can interfere with formation of
tannin-protein complexes
 Tannin-binding salivary proteins (TBSPs) bind to tannins
 Microbial activity and microsomal enzymes (produced by liver,
degrade foreign chemicals) fight toxins
o Other non-nutritive components of plants, like fibers, are selectively avoided
(leaves that have a high protein : fiber ratio are chosen
 Mechanical challenges
o Thick exo-or pericarps for protecting seeds
Responses: specialized oral anatomy in some primates, spitting, defecation of seeds
Chapter 39: Cooperation and Competition in Primate Social Interactions

Introduction: costs and benefits of group living
o Benefits: predator protection, access to sexual partners, information sharing,
infanticide avoidance, cooperative behaviors (food sharing, communal infant care,
alliance and friendship formation, coordinated hunting, range and resource defense)
o



Costs: more feeding competition & aggressive interactions, esp. with increasing
group size
Main point: this chapter emphasizes the importance of cooperation, affiliation and mutualism
in shaping primate social interactions
Rejection of the socioecological model (see ch. 28 and 29), evidence presented:
o Agonism occurs at very low frequencies among diurnal primates living in the same
social group. This does not fit the predictions of the socioecological model.
o Agonism at feeding sites does not occur more frequently among female primates that
form linear dominance hierarchies than among females that form egalitarian social
relationships. This does not fit the feeding competition model.
o Individuals in larger groups of primates do not necessarily travel greater distances
than individuals of the same species living in smaller groups. This does not fit the
ecological constraints model.
o In those cases when individuals in larger groups experience increased travel, the
energetic cost of travel for arboreal and terrestrial primates is expected to be
relatively low. This does not fit the ecological constraints model.
Alternative model
o Based on three principles
 Resources in tropical forests are found in dispersed, heterogeneous patches,
increasing the probability that several individuals have access to feeding sites
 Primates are characterized by tremendous dietary breadth
 Grouping patterns in primates are highly flexible (e.g. fission-fusion)
o The model
 Predation assumed to be high at low group size, low and relatively constant
at intermediate group sizes, and high at larger group size
 Across a relatively large range of group sizes feeding competition is expected
to be low and to have minimal fitness consequences. It becomes a problem
only at larger group size. Groups may commonly be below their maximal
size.
o

Cooperation as a non-zero sum game
Neuroendocrine mechanisms of cooperation
o Activation of reward network may positively reinforce cooperation.
 MRI studies reveal that mutual cooperation activates two main brain regions,
the anteroventral striatum and the orbitofrontal cortex, which have been
linked with reward processing

o
The strength of the neural response increases with the persistence of mutual
cooperation
 Network rich in domaine, which is released in response to positive stimuli
Neuroendocrine circuit and maternal bonding
 Hormone oxytocin is linked to parental, fraternal, auto, and sexual bonding
 Environmental factors affecting a parent can resulting changes in gene
expression in the offspring (this is called epigenesis). Oxytocin may be
regulated by epigenetic factors.
 Elevated levels of prolactin hormone predispose cotton-top tamarins to
exhibit nonmaternal infant care
Lecture 12: Affiliation and Male Bonds and Gelada Baboons


Gelada Baboons
− Habitat = endemic (exclusively native) of the Ethiopian highlands, very high up,
very dry water is a limiting factor in their habitat (birth rate is higher during
rainy season) during dry season they eat seeds and grass rhizomes (roots)
− Males have HUGE canines
− Exclusively herbivorous/veg
− Reproduction females initiate copulation
− Social Structure
 OMUs travel together and gather in bands
 Not territorial
 AMUs (all-male units that exist on the periphery of society) they forage in
the wake of the OMUs very homosexual cooperate in attacking bisexual
units (OMUs)
 Everyone grooms each other grooming between females and their males is
very important to social stability if males don’t groom their females
(leaving them unattended) they stray and form new groups
 Females can lead OMU by teaming up together to kick a male out they can
also chose between two males to lead the OMU is someone challenges their
alpha male in that sense, females have indirect control over reproductive
success
− Best strategy for an immigrant male = stage takeover or become a follower
 takeover high probability of injury success rate = 70%
 follower same reproductive success as a take over in long run
Priority of Access Model (POA) alpha male gets all copulations he wants rank
determines mating success and appropriation of females
− Exceptions = solo competition, male coalitions, energetically stressed highranking males (too many females), female choice, kleptogamy (males consort
with females in secret)
− Success and Rank
 If a data pattern makes complete sense the correlation coefficient is 1 and if
just the opposite occurs (but still a strong pattern) than the ceof is -1 if there
is no pattern the coef = 0


The priority of access model predicts male reproductive success to be a
function of rank and of the number of competing males, as well as the number
of receptive females at time of conception
 When there are few estrous females the powerful males have a HUGE
advantage guarding, consortship (taking a vacation with the female gf/bf
relationship), being opportunistic (taking any opportunity to mate that is
presented)
Male care for young why?
 Paternity confidence
 Courtship effort care is in exchange for sex
 Help is needed
Lecture 13: Competition and Cooperation and Tamarins
Primary benefits of cooperation: enhanced predator protection, increased access to
sexual partners. Info sharing, avoidance of infanticide, enhanced food sharing
Primary costs: increased feeding competition. Increased aggressive interactions
Low frequencies of aggressive behaviors and high of affiliate in most primates
Sociological model: feeding competition
- Cost of group living, role in structuring size/composition/hierarchy of primates
- Decreased food increased agonistic interactions (females more often involved)
o Role of food in female antagonism not as important factor as previously
thought…doesn’t fit feeding competition model
Ecological constraints model: travel cost
- Decrease in resources or increase group size leads to increased travel
- Increased time and energy spent, reduced time feeding and resting
- Only a minor constraint on energetic
- Larger groups don’t travel more…doesn’t fit model
w/in group feeding competition only problem if group large or in depleted environment
Neurological reasons for cooperation
- Mutual cooperation activation of anteroventral striatum and the orbitofrontal
cortex…reinforce cooperative interactions
- Dopamine system reward system
- Oxytocin related to bonding
- Prolaction relation hormone
When do coalitions pay?
1. Large clumps- between groups
2. Smaller clumps- within groups
3. Competition for safety
4. Economical defensible territory
5. Terrestrial locomotion
6. Dominance contests
Tamarins/callirichidae
C/s America
Polygynous, multimale-multifemale, or polyandry
Communal care
Complete reproductive suppression of other females only dominate female breeds
- Pheromones suppress hormonal system so they don’t ovulate
Defend territories- long day range, small home range
Undetectable dominance
More than 10 species
Polyspecific groups common dietary and anti-predator strategy
Lion Tamarin= most endangered specie in world
Cooperative polyandry- male tamarins help with infant care bc improved infant survival
Lecture 14: Mothering and Cercopithecines




Variation Between Species
o Park=leaving a child somewhere, nest-main mammal pattern; tree-primate
pattern; this is the ancestral state
o Ride=carrying a child—carry+cling are the two styles, this is a repeated
trait, evolved often and maintained
 Costs: smaller home range, late weaning, late age of first
reproduction
 Benefits; improved infant survival
o Comparison: species who use the two variations have similar IBI, growth
rate, infant size, and brain size
Mothers Importance for Survival
o Decreases with age
o Higher rank=more RS
Some Other factors that effect survival:
o Ecology: high or low quality foods—infants forage closer, suckle more,
and spend more time feeding in general in bad habitats
o Predation Risk: there is a higher infant survival rate with less predation
risk, but at young ages the rates are actually similar because the mother is
more likely to be protective (note: high rank—carry less, less restrictive)
Parent-Offspring Conflict
o Benefit to offspring=B, Cost to mother=C
o For MOM: B/2=C (only half related)
o For CHILD: 2B=C
o Conflict occurs between B/2<C>2B
o Mother is responsible for weaning and declining maternal investment
 Reject nipple contact more as age goes up
o RRI=Relative Responsibility Index

(% contacts initiated by infant)-(% contacts terminated by infant)
 As age increases, so does RRI, meaning the mother’s
investment falls (infant initiates more and terminates less)
 Note: infants seek more investment when mother is resting
or socializing than moving or feeding; rejections almost
always occur when feeding
o Hypotheses about why this decrease in investment occurs
 First some information: suckling time decreases little, females only
fertile for 20ish years
 Investment Hypothesis: 1)suckling goes down in a way that is
independent of maternal activity, 2)rejection behavior and weaning
conflicts increase independent of maternal activity, 3)total amount
of time suckling decreases significantly over time
 Timing Hypothesis: 1)suckling decreases more strongly during
activities where child is a hindrance, 2)rejection beh. And weaning
conflicts increase where child is a hindrance, 3)amount of time
suckling shouldn’t change drastically because mother is just
rescheduling, and not reducing, her investment
 This hypothesis seems to be supported
Lecture 15: Childhood and Macaques





Play
o Benefits
 Skills: males fight more than females, females play mother more
than males, female use tools more than males
 Social manipulation: mother distracting infant, learning
competition, early coalitions/relationships
 Lone play: males=females
o Economics of Play
 More play when more food (when rain increases, so does play)
 Cost: higher predation risk (distracted)
Alloparenting=when others help the mother raise the child by carrying, etc.
o Who? Mostly juvenile females, then adult f, then juv. M, then adult M
o Why?
 Nulliparous females: practice mothering, caring for kin, market
forces (get help later from high ranking female you help now)
 Parous females: nepotism, if non kin this is odd (friendship?)
 Juvenile Males: nepotism, practice mating, market forces
 Adult males: paternal care, mating effort
Random FYI, girls spend more time with mom than boys and if you decrease
testosterone, boys will spend more time with mom
Tool Use
o Girls spend more time earlier and get more termites per dip
o Girls copy their mother more
Juvenile Relationships


o F-F: depends on maternal rank
o M-F and M-M: depends on size
o Play Partners:
 Infants: prefer same size and HR
 Juv F: infants (HR preferred)
 Juv M: Juv M
Adult-Juvenile Relationships
o Double Holding: when an adult holds two infants at once—90% of the
infants that get double held are high ranking
 Females hold more than males
 Kin hold kin more than nonkin
o F-F and M-M strongest
o Adult F:
 support rank with juvenile F, supplants F as ages increases
 dominate juvenile M as long as possible (a.k.a. until he is too big)
o Adult M:
 Dominate all
 Support possible offspring
The Changing View of the Juvenile
o Past: passive, long learning period, influenced by experience, relaxed life
o New: active, fast and risky growth, influenced by social system, dangerous
life
Lecture 16: Communication, Vervets, Marmosets, and
Baboons
From Lecture:
Vervet Monkeys: Guenons (like red-tailed, blue monkeys)
- mostly terrestrial
- groom, play a lot
- dominance hierarchy strictly linear
- omnivores
- predated by terrestrial snakes, leopards, eagles (major predator), etc.
- have 3 different vocalizations: semantic in each call. Able to say whether
oncoming predator is terrestrial or aerial
- even understand the calls of the superb starling
- infants, juveniles quickly learn which birds/other animals are the biggest
threat
- fear grimace: silent, bared teeth
- open mouth = threat, “leave or I’ll be upset,” etc. many contexts
Communication: Calls, facial expressions, gestures
Calls different for different predators.
Morphology doesn’t change with age.
Responses are appropriate.
Lipsmacking: mutual reassurance gesture after an alarming situation
Duchenne smile: corners of mouth turn up and skin around eyes crinkles = happiness
smile (vs.
social smile)
Baboon “greetings”: posterior presenting, mounting, and genital touching. Most common
male interaction. The one who mounts is subordinate, as in chimps.
98% in neutral contexts, often after conflicts
One male approaches another to signal the start, then walks away at the end
7% of interactions lead to aggression
Old males greet each other this way more often. Old males need coalitions the
most to
get females
Most cooperative pairs are the most symmetrical in greetings
Do males use these greetings to negotiate and constitute their relationship?
Use reciprocal altruism: must prove that they won’t defect by investing in
the
partner/offering vulnerability
But sometimes there is a power-asymmetry
In chimps: when upset, can resort to childlike behaviors. Teeth-baring and
embracing are often used in peace-making
ears flat + chin upward = fear
Did the human smile come from this teeth-baring? Sign of submission or
appeasement?
Primate smile = food or motivation?
SBT = “silent-bared teeth” = assoc. w/ submission by the sender or occasionally
aggression by the receiver, but given more often when approached than
when approaching
ROM = “relaxed open mouth” = shown during copulation
There are a bunch of graphs, if you want to look them over. like slide 50 - on
From the Book
Chapter 38 The Conundrum of Communication
I.
Introduction
II.
The Adaptive Nature of Signal Structure
A. Signal Structure and the Ecological Environment
B. Signal Structure and “Motivational-Structural Rules”
C. Signal Structure and “Honest Communication”
How Primates Deal with Deception
Primate Communication. Linguistic Models, and the Evolution of Language
A. Vervet Alarm Calls and External Reference: Evaluating the Evidence
B. External Reference and Macaque Agonistic Screams: Navigating a
Tangled Web
III.
IV.
V.
C. Alternative Perspectives: Criticisms of the Informational Perspective and a
Reexamination of Macaque Screams
D. Concluding Remarks on Language Precursors
General Conclusions
Communication: a sender emits a signal that is detected by a receiver whose behavior
might consequently change.
Signals: have two sources: 1) acquired over time through natural selection
2) acquired through learning and convention
: in primates, can be visual, auditory, olfactory, and tactile
“honest” signal: behavior that is accurate and reliable.
handicaps: a form of communication that requires a considerable cost to produce but that
implies honest communication (e.g. sexual swellings cost a lot => assume she is
ovulating). Occurs most often between two animals who have little or no history of
interaction. However, research has found that costly signals are rarely used as the basis
for honest communication.
More common: inexpensive signals when sender and receiver both benefit from
interaction OR repeated interaction: use past interactions to determine honesty →
low-cost signals can evolve
Tactical deception: short-term changes between honest and deceptive behaviors exhibited
by an animal in the context of its social group. Behavior must be part of the normal
“honest” repertoire and the deceptive behavior must be rare, subtle, and used in different
contexts from those in which it would ordinarily appear.
Skeptical responding: process of assessing the information proffered by companions and
rivals of their own species with some considerable degree of skepticism.
Internal vs. external references: whether a signal is reflective of the signaler’s internal
state (distress) or reflective of the environment (predator).
Vervets
- “red-white-and-blue” display: males display bright blue scrotum. The brighter the
scrotum, the more dominant the male will be.
- Experiment w/ vervets showed that habituation to calls is specific to particular contexts
and individuals
- Vervet alarm calls: three types. React differently to calls responding to leopards than
they do to calls responding to eagles. Call meaning and the identity of the signaler are
important determinants of the subjects’ responses. Even respond to starlings’ calls.
Macaque
- Rhesus – victims of attacks use one of five screams, depending on class of opponent
and severity of the aggression
- noisy screams assoc w/ contact aggression from higher-ranking opponents.
- arched screams assoc w/ noncontact aggression from lower-ranking opponents
- moms respond more strongly to noisy screams of their offspring than of non-offspring,
though same not true with arched screams
Lecture 17: Cebus Monkeys and Cognition
Capuchin Monkeys = CEBUS basic description of society:
 Multi-M multi-F
 Northern S. America thru mid Central America (New World Monkeys)
 Moderate sexual dimorphism
 High Encephalization Quotient: (ratio of brain mass compared with ‘brain mass
regression line’ for an animal of their bodymass), associated with tool use—a
behavior they exhibit. Rare for such small primates.
 Slow life history (association with EQ?)
 “eclectic omnivores”—mostly eat fruit, leaves, insects but will.hunt vertebrates
opportunistically
 Vulnerable to predation from snakes, eagle, felines, etc.
 Closely related to Saimiri (SQUIRREL MONKEYS)
Female-philopatric:
 Strict linear dominance hierarchy—nepotistic, aggressive
 Female-bonded: groom each other, form stable coalitions
 Allomothering is common, esp. among low-ranking FF
No obvious male dominance hierarchy, but there is an obvious Alpha male, who:
 is usually spatially in center of group—strategy against predation?
 monopolizes mating with FF
 does not tolerate coalitions among subordinate MM
 will cooperate in defense against predators
 will search for lost group members
 just barely outranks the Alpha female, who outranks all other MM
 relies on support from the female hierarchy to maintain dominant status
Intergroup Interactions:
 are AGGRESSIVE. Females rarely participate.
 Are sometimes lethal.
 Involve male coalitions, usually only seen in fission/fusion societies like chimps
 Extragroup MM are an infanticide risk—females are protected by intragroup MM
Female rank and reproduction
 Females in LARGER groups have higher reproductive success
 All species—delayed time to reproductive maturity
 Allomaternal nursing: as rank affirmation for juveniles or adult females.
 Higher-ranking matrilines are larger and less likely to die out. Why? Maybe:
better food quality, less disease susceptibility, better predator protection.
On log-brain-volume vs. log-body-wt ration:
 capuchins, chimps, bonobos, orangs, all fall above the regression line. (humans
are way above it)

There’s a good slide comparing chips and capuchins—both hunt, use tools, form
coalitions to exhibit male aggression, develop cultural traditions.
THE BOOK
Chapter 7, the cebines
Taxonomy, diet, ecology
 Hard to determine the taxonomic relationship between cebus and squirrel
monkeys and the rest of the new world monkeys.
 There is a lot of interspecific sympatry and mixed-species associations are
observed.
 Opportunistic diet is emphasized
 Arborial: leaping plus quadrupedal movement, semi-prehensile tails.
 Capuchins specialize in building resistance to toxic foods (plants and insects) and
a lot of their observed tool use has to do with protecting themselves against
potentially-poisonous foods.
 Squirrel monkeys are on the whole a lot smaller than cebus species, and in interspecies association, capitalize on cebus’ foraging abilities, predation detection
abilities.
Reproduction
 No external signals of ovulation or pregnancy
 Frequent non-conceptive copulation
 Cebus: Elaborate courtship rituals: specific gazes, expressions, usually female
solicitation that leads into an coordinated dance. The alpha male sires the majority
of infants.
 Squirrel monkeys, on the other hand—the males get really fat leading up to
mating season and all the females prefer the fattest male—hot.
The end of the chapter is a discussion on dispersal and social grouping as related to
available resources.
Cognition
Cognition is displayed/measured in terms of:
 Learning/imitation—life history
 Ecological intelligence: spatial memory, tool use, cultural traditions
 Social intelligence: alliances/coalitions, tactical deception, ‘theory-of-mind’
Social Brain hypothesis:
 correlation between group size and ratio of neocortex : hindbrain?
 Evidence supports this hypothesis.
 Slide illustrates theory: living in groups incites competition, both intra- and
inter-group. Selection favors problem-solving in social situations.
Cultural traditions are common among species w/ ‘social brains’:
 Chimpanzees exhibit more traditions than bonobos
 Orangutans exhibit relatively few, but more than gorillas
 Capuchins exhibit a few
 Species that spend more time in association develop more cultural
traditions—evidenced by imitative learning behaviors.
Among Chimpanzees:
 More traditions are found in each group with more years of study
 Traditions are regional, socially transmitted—some lapse over time. Three clear
regions over which traditions diffuse
 All populations use tools, but for different purposes
 Traditions observed/studies: smashing fruit/nut with stone tool, “brush” stick to
fish for termites, leaf-clipping (biting without eating a leaf makes a
communicative sound, signaling that an animal is ready to mate), wiping jizz with
a leaf, “leaf-grooming,” grooming while holding hands
Tests for cognition:
 Do primates follow the gaze of conspecifics, implying that they are curious/aware
that their neighbor sees something they may not.
 Learning behavior—if the conspecific repeatedly looks at nothing, the gaze
response is inhibited (test done w/ rhesus macaques and chimps)
 Chimps move around visual barriers that block their view of a neighbor’s gize
 Among chimps: subordinates prefer to approach and retrieve food that they know
a dominant individual cannot see. (versus food that is in common sight) NOT the
case for capuchins
Tool use and Weapons among Chimps:
 Display/throwingbeating other chimps: using sticks for violent purposes is
becoming more common. Is this a socially-learned behavior?
 Using sticks to extract honey is a learned behavior among chimpanzee females
Two hypothesis about social learning, from evolutionary perspective:
 Social Learning is an adaptation reliant upon socio-ecological factors
 OR social learning is an incidental consequence of cognitive ability
FROM THE BOOK
Chapter 41: tool use and cognition



Tool use involves an object of change (the thing the tool works on) and an agent
of change (the tool itself)
Tool use in most species is highly stereotyped behavior and is context-specific.
Object manipulation, versus tool use, is extremely common in primates.—
involves only manipulating one object, not manipulating one object with another.


Repeated incidents of tool use have been observed in the following species:
chimps, orangs, cebus (capuchins), macaques, gorillas, and baboons
Tool use has been more extensively studied in captivity than in the wild
Intra-specific differences:
 As in lecture, mentions the regional differences in chimpanzee tool use
 In chimps, females show higher rates of common forms of tool use than males.
 Studies in tool use variation often focus on foraging, NOT cognitive, differences,
since tool use is so often related to food acquisition.
Definition of COGNITION: the ability to understand why and how one set of events or
behaviors is related to another.
Now, thought process (apes) vs. trial-and-error (monkeys) is being taken into account
when evaluating cognitive ability and tool use. This may imply that tool use evolved
independently in monkeys vs. hominoids.
Cognition tests—most common are:
 brain size: encephalization quotient and neocortex vs. hindbrain. Not ALL tool
users have largest brains proportionately, but pan, pongo, and cebus do. Brain size
is the only measure that correlates with tool use more than with taxonomic
distinction.
 discrimination learning: measures ‘learning to learn’ capabilities, identifying
objects, etc.—no clear correlation to tool-using species
 mirror self-recognition: being aware of oneself implies the ability to perceive the
experiences of others—‘theory of mind.’ Self-recognition is measured by
comparing self-grooming versus socially-directed responses to the mirror, or the
wiping-off-paint experiment. In general monkeys fail and apes pass.
 tactical deception: measuring capability to identify when ‘tricks’ are being
played, or to consider how much information is possessed by their conspecifics
(like dominance and concealed food experiment). Only baboons and chimps
excelled, but studies are limited. There is as of yet no clear link with tool use.
 social learning processes: imitation, gaze-following experiments: generally apes
pass and monkeys fail so a lot of these tests correlate more with taxonomic
differences not with tool-using species.
Lecture 18: Predatory Behavior and African colobus monkeys
Basic Species description, specifically about red colobus monkeys
 chute-specialists—folivorous
 arborial
 large groups—multi-male especially. Females emigrate,
 Not territorial, but males cooperate to defend the group’s resources
 Hish within-species competition
 Favorite prey for chimps, also hunted by humans
 FF alliances have been observed, as have male ‘sexual swellings’—weird.

They have a much longer life span than is expected for frequent victims of
predation—why? MAYBE: because they are arborial and can escape quickly,
because they do not have very many species preying on them, because they form
large multi-male groups.
Later in the lecture:
Chimpanzee predation stats: in gombe, mahale and tai, 5 to fifteen percent within red
colobus populations are killed each year.
 More males in group to defend it reduces predation rates
 But In gombe—large groups can ATTRACT predators
 But there is no evidence that increased population density of just any African
colobine species increases chimp predation—only red colobus. Because they’re
more tasty.
 Areas of more intense chimp predation—red colobus population mostly
juveniles—chimp predation apparently thins out the older individuals
MORE FROM THE BOOK ABOUT AFRICAN COLOBINES:
Chapter 12
 Multi-chambered stomachs allow them to digest cellulose, detoxify plant matter
 All inhabit mostly West Africa
 Eagles and leopards also predators
 Red colobus: counterattacking chimpanzees: larger groups of counterattacking
males make hunt less likely to be successful
 Polyspecific association is suspected to be a result of chimp predation
 Black and white colobus monkeys have the most varied diet, whereas red colobus
specialize on young leaves.
 Notoriously lethargic lifestyles—energy conservation
 SCRAMBLE, not contest competition—consistent with folivory—correlates with
group size, day range
 Female red colobus give copulation calls
 Infanticide is extremely rare
 Intergroup relations have been well-studied: intergroup dominance is commonly
established among red colobus species
The rest of the lecture was about PREDATION IN GENERAL.
Ecological influence on predation:
 Predation less likely to occur on larger groups
 Less likely to occur on species with larger body mass
 More likely to occur with proximity to human settlements
Eagle predation:


presence of arborial predator specifically correlated with larger primate group
size, multiM/multiF societies, Polyspecific association – increases predation
detection
more males than females are preyed upon by eagles
Cost of dispersal: recent immigrants are most preyed upon. Perhaps because they are
often at the periphery of the group
Vigilance: defined as SUDDEN predator-detection behavior.
 if it stays at a constant rate—larger group size will mean better detection
 group size will also reduce predator’s likelihood of success
 But vigilance rate not necessarily constant with group size: can increase as # close
neighbors decreases (seen in capuchins)
 Capuchin males are more vigilant (more time spent actively scanning) than
females. But they’re also a lot more vigilant closer to mating season—so maybe it
has to do with other males not predators.
 Males are also less efficient at alarm-calling, supporting this hypothesis
Chimpanzees as predators:
 More hunts with larger number of males in party
 More success per hunt with increasing number of males
 Chimp group size increases when high-quality non-fig fruits are in season, for
better foraging capabilities (so even though you’d think that hunting would go up
with lower-quality food availability, it actually doesn’t because of group size
constraints when only low-quality food is available.
 # swollen females in the group does not have an effect on hunting rate.
 Hypotheses to be tested: about the correlation between large parties and increased
hunting rate: ability to assess potential hunting success, MM competition for
sexual partners,
FROM THE BOOK chapter on predator predation: (chapter32)
Predation Rate: the frequency of successful predatory attacks for a given
group/population
Predation Risk: the rate of encounters or unsuccessful attacks. Even when rates of
successful predation are low, risk (encounter) can still be high.
Dilution effects: increasing vigilance, improved group (mob) mentality with larger
groups. Formation of mixed-species groups reduces predation risk.
Tradeoff between foraging capabilities (also sleeping habits) and increased vigilance.
There are rare instances where counter-attack is more beneficial for the prey.
Distress calls are a last-ditch effort—startle response
Prehistoric hunting may account for much of today’s distribution of primates.
Are humans a fundamentally-unique kind of predator, because they arm themselves with
projectiles, and sharing characteristics of both ambush and coursing predators.