sexual selection and gibbons readings: chapters 16 and 26
TRANSCRIPT
![Page 1: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/1.jpg)
Sexual selection
and
Gibbons
Readings: Chapters 16 and 26
![Page 2: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/2.jpg)
![Page 3: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/3.jpg)
![Page 4: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/4.jpg)
Gibbon
![Page 5: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/5.jpg)
Body weight in gibbonsM = F, or M 10% heavier
Sexual selection Body mass & social structure
![Page 6: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/6.jpg)
Sexual “monomorphism” in monogamous species...... Is not necessarily associated with lack of aggression.
Sexual selection Canines
![Page 7: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/7.jpg)
Sexual selection
Testis size
(scramble competition)
![Page 8: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/8.jpg)
![Page 9: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/9.jpg)
Testes larger in multi-male species: Scramble competition
![Page 10: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/10.jpg)
Testes larger in multi-male species
![Page 11: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/11.jpg)
Testes larger (than expected) in multi-male species
![Page 12: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/12.jpg)
Adult male chimpanzee, Kanyawara
![Page 13: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/13.jpg)
Integrating 3 effects of sexual selection
M=F
![Page 14: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/14.jpg)
Monogamy Polygyny
Polyandry
Multi MM-FF
GGorillaGibbon
Chimp
Tamarin
![Page 15: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/15.jpg)
![Page 16: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/16.jpg)
![Page 17: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/17.jpg)
Exaggerated Swellings mostly in Multi-Male Societies
Multi-Male species with Exaggerated Swellings have more than twice as many MM per breeding units(4.3 versus 1.8).
Ovulation at peak of swellings but …
…There is a high variation as to when exactly ovulation occurs.
Multi-MMMangabeys: 12 daysMacaques:5-20 d.Baboons: 6-10 d.Chimps: 6-9 d.
Monogamous-1MGibbons: 6 daysGorillas: 1 day !
Exaggerated SwellingsServe contradictory purposes for FF:
1- Increase paternity certainty (because dominant MM guard the FF around maximum swelling).
2- Confuse paternity (because of high variation of ovulation around maximum swelling)
Nunn, 1999. Anim Behav.
![Page 18: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/18.jpg)
Male penile sexual functions
Display
A. To female: chimpanzee
B. To male: baboon
Sperm plug removal (?)
Chimpanzee, bonobo,
muriqui
Spines: “stimulate females”
Lorisoid
Twig (Adult M), Kibale N.P.
![Page 19: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/19.jpg)
Dispersed mating systems
MM-FF mating system
![Page 20: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/20.jpg)
Penile morphologies are LESS divergent in polygynous mating systems than MM-FF or dispersed mating systems. Why?
![Page 21: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/21.jpg)
Male genital morphology: human penes fit multi-male
= size and form of external
penis
![Page 22: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/22.jpg)
Monogamy and sexual selection
Unexpected: MM “should” compete for several FF (Female dispersal cf. food?)
Rare in mammals (3%?)
Primates: 15% (1970s-80s) 3-8% (1990s)
Distinct types
Callitrichids: include helping, reproductive suppression
Gibbons: territorial
Nocturnal primates = separate day range, yet exclusivity.
Definition of Monogamy:
“A prolonged association and essentially exclusive mating relationship
between one male and one female.” (Wittenberger & Tilson 1980)
![Page 23: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/23.jpg)
Gibbons (Hylobatidae)
![Page 24: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/24.jpg)
Gibbons or “lesser apes”
Hylobatidae
![Page 25: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/25.jpg)
Gibbons.
8-10 species, SE Asia
5-8 kg
10-15 kg
![Page 26: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/26.jpg)
GibbonsMostly allopatric
![Page 27: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/27.jpg)
Weird species colors:
F/M same
F/M different (sexual dichromatism)
Variable within sex (gold/dark)
![Page 28: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/28.jpg)
Terminal branch specialists
Frugivory predominates (+ leaf)
F normally leads foraging activities
MM respond first to predators
High survival within groups
MOVIE
![Page 29: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/29.jpg)
Territorial defense
47% over food trees (Bartlett 1999)
Males do most of the fighting
Females mutually repulsive to each other
Benefit of food territoriality
Defense of specific food patches
Highly efficient (25% territory seen every day!)
Gibbons know their fruit patches very well
![Page 30: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/30.jpg)
Trivers-derived model of monogamy.
Females defend territories
Males defend females.
Pro:
Explains “monogamy without male PI”
Fits “MM investing in FF” > “FF in MM”
Con:
Females don’t in fact establish territories
![Page 31: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/31.jpg)
Activity patterns
20-50% resting
Little social activity
(mode = 1% of time grooming! cf. chimps 10-15%)
N.B.
Grooming model: competition to get favors
Evidence: groom up hierarchy (for aid down)
groomers are rewarded later
(chimps w/ food; vervets w/ support)
Reward is mainly the bond
![Page 32: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/32.jpg)
Gibbon monogamy
Isolated pairs (unlike humans)
Long-term pairs (e.g. 3 pairs stable for 7 years)
(but: high divorce rate / adultery)
No helpers
Mating only for conception
(unless 2nd male)
Co-dominance or F > M
MM groom FF > FF groom MM (~80-90%)
(FF more when first paired!)
Strong territoriality
![Page 33: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/33.jpg)
Call: species-specific, variable patterns
8 spp
F calls ---> M calls (+ overlap)
? = “This is my land” ---> “This is my female”
[Widowed F: F can mimic M presence]
5 spp
M long solos MOVIE
![Page 34: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/34.jpg)
Dispersal and family formation
No sex bias in dispersal
Habitat saturated
- Empty territories quickly occupied
Solitaries disappear, die?
Ecological Constraints Hypothesis for Incest
Young adults should stay as long as possible
Kin less hostile than non-kin
Young may assist in range defense
Young may take over parental slot incest!
![Page 35: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/35.jpg)
Why be monogamous?
*Female needs male help? NO!
Male does no caring for offspring
(except in one species: siamang, carries juvenile)
*Sexual selection: YES?
Male strategies depend on female distribution
F defends territory (but this does not work in gibbons...)
M defends F
*M aids in predator defense?
Looks trivial
![Page 36: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/36.jpg)
Benefit to female of being consorted by male
*Range defense
Wins battles over food (e.g. 45% interactions over food)
M fights while F eats
*Infanticide defense? (van Schaik & Dunbar 1990)
Possible because there is a paternity certainty
Puzzle: why does M stay, if he could defend 2 ranges?
No attempts seen.
Lone mothers don’t call
*Mate-guard (Palombit 1999)
F accepts M because hard to remove him
M benefits by ensuring paternity
![Page 37: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/37.jpg)
“Extra-pair copulations could be a serious threat to a male’s paternity; the group A female in the Khao Yai Park study area has been seen copulating with at least 4 different neighboring adult and subadult males over the past 15 years. These extra-pair copulations all occurred while the resident A-male was not accompanying her.”
(Brockelman 2004)
“A male often has to leave his mate unprotected to defend the territorial border” (Brockelman)
What if: conflict between mate-guarding and range-defense?
Range-defense wins...
“Mate guarding and territorial defense are demanding and often mutually exclusive activities”
![Page 38: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/38.jpg)
Is Territorial Defense a form of
Mate Guarding?
![Page 39: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/39.jpg)
Problems with view of monogamy
> 2 adults
H. concolor 25% groups
H. hoolock 12%
H. lar 10-18%
H. agilis 0%
Palombit,Fuentes (2000)
*Polygyny (esp. northern, more leaf-eating species, e.g. concolor)
F joins F-M pair if allowed to do so
*Movement
F leaves M1, joins widowed M2, mates with M2-M3-M4, rejoins M1
![Page 40: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/40.jpg)
Exceptions to territoriality
Affiliative encounters
Khao Yai: 25% of one group’s encounters
Note: Khao Yai = 2nd largest NP in Thailand
e.g. M plays with juveniles of other group
(uncle!)
Bartlett (2000)
![Page 41: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/41.jpg)
SUMMARY:
Reality:
Males defend territories
Females defend if necessary
Females are not effectively mate-guarded
Little infanticide pressure indicated
Hypothesis:
Females need a territory, defended as well as possible
Males constrained to defend territory for female
White-handed gibbon(Hylobates lar)
![Page 42: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/42.jpg)
2- Male maintains a bond with a single female to increase paternity certainty (infanticide) (van Schaik and Dunbar, 1990)
3- Male seeks to maintain future mating opportunities (Palombit, 2000)
Three hypotheses to explain the male’s commitment to one female
Brockelman in press
1- Males attach themselves to females and defend their access to mating opportunities (Wrangham, 1979)
Are these hypotheses mutually exclusive?
![Page 43: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/43.jpg)
![Page 44: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/44.jpg)
See Chapter 17 (orangutans)
![Page 45: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/45.jpg)
e.g. sexual swellings
e.g. Good gene theory
e.g. M looks strong
![Page 46: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/46.jpg)
Sexual selection of
specific characters ?
![Page 47: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/47.jpg)
What about
humans ?
![Page 48: Sexual selection and Gibbons Readings: Chapters 16 and 26](https://reader036.vdocuments.net/reader036/viewer/2022062716/56649dd35503460f94ac9a79/html5/thumbnails/48.jpg)
Fuentes (2000)
Gibbon ‘community’ concept
“Neighborhood” ?? -- maybe
“Community” -- No --- no joint action.