Primatology - life history + reproducing

Menopause
Short reproduction intervals
Grandmothers can help raise grandchildren

Late maturation ----> long juvenile period ----> long maternal investment
Slow reproduction (average interbirth interval 2.3 years)
Limits no. of offspring (normally just one at a time - max. 2 in Callitrichids)
Low adult mortality, long reproductive career
Long life span
Females live longer than males (more equal in cooperative species)

Selective process acting on behaviour and traits that maximise reproduction
Trade-off between natural selection and sexual selection adaptive value of traits

Intrasexual selection
Intersexual selection

Intimidating, deterring or defeating same sex rivals

Making themselves attractive to the opposite sex (mate choice)
Opposite sex reproductive strategies differ and compete (creates sexual conflict)

Maximises lifetime reproductive success

Males ready to mate most of the time
Females constrained by physiology (limited no. of receptive females)

Male-male competition
Mate choice - females choose among potential mates

Variation in the size of physical traits between males and females

Sexual dimorphism:
- Larger body size
- Physical weaponry
- Vocal apparatus
- Secondary sexual characters (male orangutans have flanges - developed during maturation)

Higher sexual dimorphism in mating systems with one single reproductive male
Harem
Plavcan 2012

Sperm competition - reflected in size of testes
Chimpanzees in multi male groups - above allomatric scale
Gorillas below
High sperm competition in multi-male societies
Harcourt et al 1995

Attractiveness of certain traits (resource holding potention (RHP) = capacity to provide protection, parental care, resources, provide good genes (refelcted by good health))
RHP often given by honest signals by males

Characteristics in males that display their good genes, good health/condition, therefore high potential for resource holding

Colourful ornaments

Brightly coloured Mandrill males get more copulations - increased chances to sire
Females approach more brightly coloured males
Females present more to brightly coloured males
Setchell 2006

Males and females prefer different reproductive strategies to reach optimal fitness
Conflicting optimal fitness strategies concerning reproduction
Evolutionary arm race between males and females

Male reproduction is cheap (invest in numerous gamete with no energetic reserves - ready to mate most of the time)
Females reproduction is costly: invest in few gametes with high energetic reserves, invest
in costly maternal investment (gestation, lactation, maternal care - constrained by energetic needs to store reserves)

eggs, gestation, lactation, maternal care
-> reproductive mistakes are costly
-> females are choosy – mate choice
-> males are limited by access to females

Reproductive strategies implicate on space use

Females: high investment in offpsring (gestation, lactation, maternal care)
Limited by the access to resources (food)

Males: low investment in offpsring
Limited by the access to females
Search for more matings

Dominance hierarchies
Intrasexual competition for resources

Number of offspring they can produce

-> compete among females for better resources (shorter inter-birth interval, higher survival, better offspring survival, better health)
-> monopolize resources (keep/take greatest share of)
-> dominance hierarchies
-> matrilines

Indirect fitness advantage: access to food resources
Direct fitness advantages: survival (higher rank = survive longer)
Faster reproduction (shorter inter-birth intervals) with higher rank
Reproductive success: high variance in reproductive success

Dominance hierarchies
Coercion
Infanticide
Female defence
Resource defence

Variance in reproductive success is high
High ranking > low ranking
High reproductive skew in males (high ranking males have most reproductive opportunities)
Top sire each year produced 24% offspring, 71% troop = NO offspring at all
Widdig et al 2004

A form of sexual conflict
Males attempt to bias mating in their favour by:
- harassment
- intimidation (aggression)
- forced matings

leads to:
-> a higher rate of potentially fertile matings
-> a lower rate for other potential mates
-> costs for the female
Female counterstrategies - Costlier investment from females to counteract coercion

Old World Males > New World Males in coercive strategies
Clarke, Pradham and van Schaik 2009

Female coalition in Bonobos against male coercion
Female dominance
"When females formed coalitions, 100% won against target male"
Tokuyama and Furuuichi 2016

Increased male reproductive success
Hrdy 1977, 1979
Faster reproduction (Species with lactational amenorrhea, short male tenure, resumes female cycle so sexually receptive)
Infants of other males targeted (done by new males, and not with females who they have mated with prior)
High chance of siring new infants in dominant males in one-male groups
Hirawai-Hasegawa 1988

Paternity confusion:
-> Promiscuous mating (in multi-male, multi-female social systems)
-> Synchrony of reproductive cycles of all females
-> Zinner et al 1994 found more females synced = reduced probability of males siring offspring
-> Post partum oestrus (time after birth, no post partum oestrus = more lactation)
-> van Schaik and Kappeler 1997 found specied with no oestrus after birth had high infanticide rates
Male-female association (females spend more time with males after birth of infant, and less time after death of infant)
Palombit et al 1997

Males directly defend access to one or more females via:
Long term association (monogamous bonds, harems)
Dominance hierarchy (in mixed sex groups, dominant males have priority access, form short-term courtship bonds)
Coercion

Solitary dispersed
Pair bonded
One female multi-male groups
One male groups ("harem")
Multi-male multi-female groups
Fission-fusion communities
Multi-level societies / modular societies

Forage alone
Social contact via vocal and olfaction (scent marking)
Often nocturnal
Polygynous
Eg. Orang-utans

One male, one female
Territorial defence
Monogamous
Extra pair copulations
Parental offspring care
Eg. Hylobatids (gibbons etc.)

Cooperative breeding
Reproduction of subordinate females suppressed by aggression/pheromonal signals
Polyandrous
Cooperative polyandry
Eg. Multi Male - MarMosets

Single reproductive adult male defends territory with several females and subordinate males
Exclusive mating access
Polygynous
Bachelor groups
High infanticide risk
Sexual dimorphism
Eg. gorillas

Polygyandrous
Males and females mate with several members
Female philopatry
Matrilines
Exaggerated sexual swellings
Eg. macaques

Temporary sub-groupings depending on food conditions
Male philopatry
Female dispersal
Eg. chimpanzees

3 levels of social structure:
-> one male units (reproductive unit)
-> bands (ecological unit)
-> troop (temporary aggregations)
Polygynous
Infanticide
Eg. geladas

Monogamous = 1M, 1F
Polygynous = 1M, 2+F
Polyandrous = 2+M, 1F
Polygynandrous = 2+M, 2+M

2001
Studied multi-male, multi-female group of Japanese macaques
Found socially dominant males monopolised most female matings
Lower ranking males avoided competition by engagning in secret copulations with females away from other males
Sexual conflict:
Males = mate guarding by high ranking males
Females = mate with several males of varying dominance rank