Determinants of male Determinants of male reproductive success in wild reproductive success in wild long-tailed macaques—male long-tailed macaques—male monopolisation, female mate monopolisation, female mate

choice or post-copulatory choice or post-copulatory mechanisms?mechanisms?

Shay Omahen, Sam Sotuyo, Seth Shay Omahen, Sam Sotuyo, Seth MatsumuraMatsumura

Engelhardt, A., Heistermann, M., Hodges, J.K., Nurnberg, P., & Niemitz, C. (2006). Determinants of male Determinants of male reproductive success in wild long-tailed reproductive success in wild long-tailed macaques—male monopolisation, female macaques—male monopolisation, female mate choice or post-copulatory mate choice or post-copulatory mechanisms?. mechanisms?. Behavioral Ecology and Behavioral Ecology and Sociobiology, 59, Sociobiology, 59, 740-752. 740-752.

Video, Male Reproductive Video, Male Reproductive StrategiesStrategies

• http://www.youtube.com/watch?http://www.youtube.com/watch?v=sMa9FdNM5iov=sMa9FdNM5io

IntroductionIntroduction• Contest among males for access to mates Contest among males for access to mates

should lead to social systems with alpha should lead to social systems with alpha male.male.

• Findings show that complete Findings show that complete monopolization of females are difficult monopolization of females are difficult resulting in lower status males having resulting in lower status males having paternity. paternity.

• What other mechanism operate in What other mechanism operate in paternity determinism?paternity determinism?– Synchrony in female ovarian cyclesSynchrony in female ovarian cycles– Fighting abilityFighting ability– Coalition forming by subordinate malesCoalition forming by subordinate males– Mate guardingMate guarding

• Female choice also plays a role in paternity Female choice also plays a role in paternity determinism.determinism.

MethodMethod• Consisted of a group of long-tailed Macaques Consisted of a group of long-tailed Macaques

from the Ketambe Research Station in from the Ketambe Research Station in Indonesia.Indonesia.– 8 adult females8 adult females– 5 adult males5 adult males– Several sub-adults/juvenilesSeveral sub-adults/juveniles– 2 infants2 infants

• Fecal matter was collected from: Fecal matter was collected from: – females to determine ovulation cycle and females to determine ovulation cycle and

pregnancy.pregnancy.– Infants to determine paternity.Infants to determine paternity.

• There were 2 different ovulation cycles:There were 2 different ovulation cycles:– KA (estrogen levels were elevated but ovulation did KA (estrogen levels were elevated but ovulation did

not occur)not occur)– SA (estrogen levels elevated and ovulation did SA (estrogen levels elevated and ovulation did

occur)occur)

Behavior ObservationBehavior Observation

• Two or three observers followed a group of Two or three observers followed a group of Macaques for a mean time of 11.1 hours and Macaques for a mean time of 11.1 hours and recorded any sexual interaction between recorded any sexual interaction between adult group members.adult group members.– Female approaches male and vice versaFemale approaches male and vice versa– Mounting behaviorsMounting behaviors– Refusal of sexual interactionRefusal of sexual interaction– Forced copulationForced copulation

• Dominance hierarchy was determined by Dominance hierarchy was determined by display of “bared-teeth-face” display of “bared-teeth-face” (submissiveness). (submissiveness).

ResultsResults• 11 ovarian cycles were observed11 ovarian cycles were observed

– 6 conception cycles6 conception cycles– 4 ovulatory non-conception cycles4 ovulatory non-conception cycles– 1 anovulatory cycle1 anovulatory cycle

• 6 out of 11 cycles females were consorted by alpha 6 out of 11 cycles females were consorted by alpha males 97% of the time (SA). males 97% of the time (SA).

• Remaining 5 cycles (KA, non-monopolization), alpha Remaining 5 cycles (KA, non-monopolization), alpha males consorted females 26% of the timemales consorted females 26% of the time

• More mating partners observed during KA, but most More mating partners observed during KA, but most copulations were observed by alpha males.copulations were observed by alpha males.

• During SA, dominate males chased females away from During SA, dominate males chased females away from other males 30% of the time (mate guarding).other males 30% of the time (mate guarding).

• Sneak copulations by subordinate males were very low Sneak copulations by subordinate males were very low while being consorted by an alpha male.while being consorted by an alpha male.

• All 6 infants born during the period were fathered by All 6 infants born during the period were fathered by high ranking males.high ranking males.

• Females also mated more often with higher ranking Females also mated more often with higher ranking malesmales

DiscussionDiscussion• Monopolization of females is timed Monopolization of females is timed

according to the females SA cycleaccording to the females SA cycle– This ensures paternityThis ensures paternity– Monopolization not seen during KA; would Monopolization not seen during KA; would

be a waste of energy.be a waste of energy.• Mate guarding was observed during this Mate guarding was observed during this

periodperiod– 3 of the 6 infants conceived during the SA 3 of the 6 infants conceived during the SA

cycle had alpha males who guarded the cycle had alpha males who guarded the females throughout the entire fertile phase.females throughout the entire fertile phase.

– Resulted in very minor proportion of Resulted in very minor proportion of copulations by subordinate males during SA copulations by subordinate males during SA cycle.cycle.

DiscussionDiscussion• Subordinate males tend to be insistent Subordinate males tend to be insistent

while mating. Those rejected by females while mating. Those rejected by females would simply try again and would be would simply try again and would be successful. successful. – Caused females to be sexual permissive by Caused females to be sexual permissive by

harassment and intimidation. harassment and intimidation. – Forced copulations were observed but were Forced copulations were observed but were

very rare. very rare.

• Coalition formations by subordinate males Coalition formations by subordinate males were expected but none were observed. were expected but none were observed. – Could be due to fear of retaliation by an alpha Could be due to fear of retaliation by an alpha

male. male.

Critical ReviewCritical Review• Liked:Liked:

– All the subordinate males had to do was be All the subordinate males had to do was be persistent in order to mate with a femalepersistent in order to mate with a female

– Dominant males father most of the offspring Dominant males father most of the offspring ultimately making their offspring carry on the ultimately making their offspring carry on the good genesgood genes

– In all of the cycles, consortships were male-In all of the cycles, consortships were male-maintained in 100% of the consort time.maintained in 100% of the consort time.

• Disliked:Disliked:– The sample size was too smallThe sample size was too small– The observation time was for a few months (11 The observation time was for a few months (11

ovulation cycles)ovulation cycles)• Which only allowed for 6 pregnanciesWhich only allowed for 6 pregnancies

– The descriptions of the 2 types of ovarian cycles The descriptions of the 2 types of ovarian cycles were unclearwere unclear

Test QuestionsTest Questions1)1) T/F: Fecal matter was collected from females to determine ovulation T/F: Fecal matter was collected from females to determine ovulation

cycle and pregnancy.cycle and pregnancy.2)2) T/F: During non-monopolization cycles, alpha males spent more T/F: During non-monopolization cycles, alpha males spent more

time consorting with females then during monopolization periods. time consorting with females then during monopolization periods. 3)3) T/F: Mate guarding was observed to be an effective method of male T/F: Mate guarding was observed to be an effective method of male

reproductive successreproductive success4)4) Dominance hierarchy was determined by display of:Dominance hierarchy was determined by display of:

A: pacingA: pacingB: bared-teeth-faceB: bared-teeth-faceC: hair to body ratioC: hair to body ratioD: groomingD: grooming

5)5) Which of the following behaviors was NOT observed:Which of the following behaviors was NOT observed:A: Female approaches male and vice versaA: Female approaches male and vice versaB: Mounting behaviorsB: Mounting behaviorsC: Nuptial giftsC: Nuptial giftsD: Refusal of sexual interactionD: Refusal of sexual interaction

6)6) SA cycle describes:SA cycle describes:A: estrogen levels elevated and ovulation did occurA: estrogen levels elevated and ovulation did occurB: estrogen levels were elevated but ovulation did not occurB: estrogen levels were elevated but ovulation did not occurC: estrogen levels were decreased inhibiting ovulationC: estrogen levels were decreased inhibiting ovulationD: none of the above D: none of the above