Hamadryas Baboons

Hamadryas vs Savanna Baboons

Hamadryas…

Arabia, N-E Africa: dry country, less fruit, less grass?

Separate ~340,000 years

Hamadryas 20-25% smaller

Dimorphism: H MM striking from 3-4 years

Long mane; white whiskers; pink face, perineum

Fertile hybrids --- same species! Papio hamadryas

e.g. Hamadryas: Papio hamadryas hamadryas

Anubis: Papio hamadryas anubis

Troops = Sleeping groups

Hamadryas Social Organization

Troop: Up to > 600

Sleeping community only

Band: Largest social unit (~ 30-100)

May travel together or disperse

May fight other bands

No M-M fighting within bands

Clan: “Sub-band” (~10-20)

May forage independently

MM may look alike (e.g. Reds)

Little M/F dispersal

Rosso and Rossini of the Red Clan - they look alike.

Fights between bands

Inter-band supplanting

Fights between bands

Near band approaches. Fight starts on right.

Fights between bands

Inter-male contest for FF

M(R) chases M(L)’s F. M(L) intervenes.

1

2

Fights between bands

FF in M(L)’s attack shadow. M(L) does not “engage in battle”.

Body weight : FF 14.7 kg; MM 28.4 kg (twice FF’s body weight !)

Family (“one-male unit”) within clans

Prime M, FF (2-3, range 1-9); M = leader

70% bonds last > 3 years

M dominates FF within unit

Most grooming is by F to M

M can summon F with a look

M defends his infant

Certainty of paternity?

High-ranking mothers are more permissive parents.

Low-ranking mothers keep tight control on their infant’s whereabouts, sometimes by holding her infant by the tail.

N. Rowe, 1996

M intervenes if any other M tries to interact with his females

FF compete for M (e.g. by being child-like)

Female-female aggression within OMU: coalitions only with male!

Like among gorillas

Female-female aggression within OMU: coalitions only with male!

“Double signal” by female. Present to M; threaten opponent F.

“Protected threat” (seen only in captivity).

F(A) moves so as to be between M and F(B) (and presents to M).

So F(B) can’t threaten F(A) without threatening M also.

Paternity

Strong M-M respect:

No matings seen by other males within clan

Contracepted MM : FF stop breeding

FF solicit their own MM only

Anti-infanticide strategy by FF?

Coordination

How to meet at water-hole after leaving sleeping-cliff?

1. Mental map? Probable.Places visited more often are reached by more detours.

2. Communication of intention? Probable.

Clans separate 250 m from cliffReassemble at noon to drink/restJoint direction pre-fission (250 m) = waterhole directionNotifying at high rates Male “notifies” to ally (before turning R)

Ho: MM “make appointments” within bands

Life-history of hamadryas OMU

1. Initial unit.

Young AM (9-11 yr) + Juv F (2-3 yr)

No mating (F too young)

M herds, carries, sleeps-embracing F

M hugs juv F, initial unit

1. Initial unit

Formation

“Follower-M” forms bond with Juv F

M herds; lie flat and watch; walk ahead / look back

invite groom.

N.B. This establishes ‘respect’ by other MM before FF mates

Nervous mother

Grooming between MM of initial units

N.B. No grooming among breeding males!

1. Initial unit

‘Maternal’ Male in initial unit

1. Initial unit

2. Take-over Fight

Prime M loses FF to

(A) Non-breeding M within clan (e.g. Follower M)

or (B) Neighboring band

but No fight/take-over within the clan (M-M “respect”)

Question: Higher risk of take-over if more FF in the OMU?

Male stages within clan

Past prime BACHELOR; FORMER LEADER

Prime OMU LEADER

Late adolescent INITIAL UNIT LEADER; FOLLOWER

Early adolescent BACHELOR; FOLLOWER

STATUS

How do MM in OMUs avoid losing FF?Kummer’s field experiments

1. What creates the Hamadryas M-F bond?

Ho: Male herding behavior.

Transplant Anubis F into Hamadryas band

1 H-M “herds” (rocks cage, neck bite, expects follow etc)

A-F follows within 1 hour!!

Conclusion: H-M herding -> M-F bond

BUT: A-F keeps straying!!!

After a week, H-M gives up!!

Conclusion: H-M herding + H-F following -> M-F bond

Transplant H OMU to different H Troop! (at dawn)

--> M loses FF within 1 hour

Conclusion: M-M respect within bands protects the M-F bond.

2A. What protects the Hamadryas M-F bond within Bands?

Ho: Breeding MM within Bands respect each

other’s relationships with FF.

2B. What protects the Hamadryas M-F bond within Bands? Mechanism?

Test M-M dominance within a Band (HM1, HM2)

e.g. peanut test --> (HM1 > HM2)

Introduce new F to Low-rank M (HM2)

Allow high-rank HM1 to watch for 15 minutes (cf. Control, watch 0 min)

Introduce dominant HM1 to (F + subordinate HM2)

--> HM1 is inhibited

cf. Control, HM1 attacks!

Conclusion: M-M respect within bands results from knowing M-F bond.

Ho: MM respect within Bands comes from observing M-F relationship.

F has been placed on top of HM1’s cage.

HM1 moves as far as possible, and turns away.

HM2 grabs for F without inhibition.

2B. What protects the Hamadryas M-F bond within Bands?

Ho: MM respect within Bands comes from observing M-F relationship.

Control experiment: MM do not

observe each other with F.

Result: High-rank M wins.

Conclusion: M-M respect within bands results from knowing M-F bond.

2C. Does F choice influence M respect?

Ho: MM show less respect to the M-F bond if FF don’t like their own M.

Test: Rank F preference for M: approach, groom, etc

Allow Rival MM to attack/respect

Result: MM attack more if F preference for her

own M is low.

Conclusion:

M-M respect within bands results from

1- M1 knowing M2-F bond, AND

2- from assessing F’s preference for her own male.

Species differences in Sexual Behaviors

Anubis Hamadryas

♂

♀♀

♀♂

♂

♂♀

♀♀

♂

AnubisHamadryas

♂ ♀♀ ♀

♂ ♀♀ ♀

♂ ♀♀ ♀

♂ ♀♀ ♀

♂ ♀♀ ♀

♂ ♀♀ ♀

BandClanOMU

Hamadryas (compared to anubis):

• less fighting

• no dispersal

• more sexual consorting

Species differences in Sexual Behaviors

Anubis Hamadryas

Species differences in

SerotoninAnubis Hamadryas

• Serotonin is neurotransmitter and hormone.

• It acts as a sexual inhibitor.

• When serotonin is reduced in the body (with a neurotoxin), sexual

activities are increased in male rats.

Dixon (1998). Primate Sexuality

• Increasing the serotonin activity in the brain (with drugs) result in

reductions of sexual behavior in male rats, or…

• … inhibits erection in the male rhesus monkey

Hamadryas baboon

Savanna (anubis) baboon

SEROTONIN & BEHAVIOR: VARIATION BETWEEN SPECIES

Hybrids: inhibited males

Kaplan et al (1999)

Anubis Hamadryas(hybrid)

Serotonin index

Species differences in

SerotoninAnubis Hamadryas

See you next time !

Hybrid troops

Morphology and Behavior correlated in the hybrids?

Score MM by 7 physical features (e.g. mane length)

7 behavioral features (e.g. herding)

Result: Hybrids: behavior and looks are correlated.

Complex mixture of relationships… some bonding, some not

Origin: Hamadryas “Mate-raiding”? Expected, but not seen

Immigration by Hamadryas and Anubis MM -- yes

Hamadryas and evolutionary history.

Hamadryas and anubis differ consistently (wild + captive)

Female coalitions (H-, A+)

Female willingness to be herded (H+, A-)

Male herding (H+, A-)

Male respect (H+, A-)

What explains the Hamadryas system?

Kummer/Dunbar: male protects vs. predators

Henzi/Barret: male protects vs. infanticide

A. Low food density --> small groups

Wrangham: FF coalition in Indian langurs against Infanticide

FF coalition in olive and yellow baboons Infanticide rare

But chacma: FF allies occur but rarely, similar to Hamadryas!