rare ectotherm biparental caresraylman/behavioral/10parentalcare.pdfparents may naturally invest...
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Burying beetles, clownfish
Rare ectotherm biparental care
Parent beetles bury, defend, shave, roll, ‘inoculate’ carcass
Clownfish don’t have opportunities to desert
Trade offs:
offspring quantity vs. quality within a brood
current vs. future offspring
Determining optimal parental investment per offspring
From the point ofview of the parent
Tradeoffs shown in gobies, lizards, burying beetles, flycatchers p.228
Male vs female care influenced by chance of future RS, amount of brooding benefits
Flexible care – influence of costs and benefits
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Another factor that determines if you care is what your mate does.
Who cares?
P = offspring survival prob.p = probability to mate againW = # young, fem. desertsw = # young, fem. cares
In fish, W often >> w, so if P1>>P0 you will get care
In birds P2 often >>P1
What if a mate ‘cheats’ by offering reduced care?
Mate should compensate, but not fully
Model both supported and refuted
Mate conflict over biparental care
Parent - offspring conflict
Parents and offspring share 50% genes
Conflict occurs over parent’s allocation 1) within a brood and 2) towards current vs. future offspring
How much should parents care?
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POC predicted in a model by Robert Trivers
Parent offspring conflict over length of parental care
Parents may allocate according to the value of their young. Offspring try to manipulate parents for more care.
Look for honest signals of health
Assessing value
Intra- and interbrood conflict
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fur seal lactation conflict
Intra- and interbrood conflict
Booby siblicide
Parents may naturally invest more in some young and less in others. Ex: hatching asynchrony
Bias in care can lead to siblicide
Siblicide and parental manipulation
Sibling eviction
Function of hatching asynchrony
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Kookaburras – 3 eggs in a clutch, but half the time not all will survive due to resources. Chicks try to kill each other
Cattle egrets – Female lays 3 or more eggs but only rarely will all survive – 1st egg is provisioned with testosterone
Siblicide in birds
Mating systems
Monogamy
Polygamy
Polygyny
Polyandry
Polygynandry (Promiscuiity)
Basic types of mating systems
Generally, different forms of polygyny
The form of polygyny depends on how females are dispersed around, influenced by:
Mating systems: no paternal (male) care
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Scramble competition polygyny Resource defense polygyny
Lek/chorus polygyny Harem defense polygyny
(can be seasonal only)
Constrained monogamy
So..will the females clump?
Operational sex ratio and synchrony of female availability, no male care
Timing can be everything
horseshoe crabs
‘Explosive’ synchronous breeding can limit multiple mates for males
two male butterflies wait for afemale to emerge from cocoon
Females solitary, unpredictable, synchronous breeding. Males selected for persistence and speed. Scramble competition polygyny
milkweed leaf beetle
13-lined ground squirrel
Mating systems: (no male care)
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Majority of mammal species: females solitary, males overlap their range w/several females
Facultative polygyny
Mating systems: (no male care)
Female ranges
Male ranges
Breeding
habitat
Females social, their RS depends on resource that males can defend
Resource defense polygyny
long-horned beetle malesdefend foraging areas
hoary marmot males defendfeeding areas - food is scarce
Languar males ownsharem in his territory
Mating systems: (no male care)
Females social but roaming or seasonal
Harem/female defense polygyny
Mating systems: (no male care)
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Polygynandry: when both genders have multiple mates. Females are usually in groups
Multiple males defend group (lions)
Groups meet up temporarily with male groups (dolphins, elephants)
Mating systems: (no male care)
Leks or chorus (Lek polygyny)
Males clump - No resource or harem defense, females often have large ranges
Female choice is extreme - center male gets most of the matings groups of 100+ males
fallow deer
lesser short-tailed bat
sandpipers
Mating systems: (no male care)
Success for males on leks
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Why do males join these leks?
Hotshot hypothesis
Stimulus pooling
Hotspot hypothesis
Female choice hypothesis
Hotspot: Males follow pattern of female dispersal
Leks can occur at same spot year after year
Stimulus pooling:
More females are attracted to a set of males than separate male – increased signaling
Rewards to males increase with lek size
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Hotshot: Poor signalers parasitize the attention gained by highly attractive males
Some manipulations don’t support
great snipe
fallow deer
Female choice:
Leks form because they allow females to make the best choice. Females choose vigorous males
Females ignore males that aren’t in leks
How to increase RS when resources cause home ranges to overlap w/just 1?
Obligate monogamy (p.257)
Breeding
habitat
Mating systems with male care
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Obligate monogamy with biparental care
Removal of a mate results in large RS failures
Mating systems with male care
Polygynandry with male care – ostriches
Dominant males and females form bonds, but also mate w others. Communal nests are formed with eggs of multiple females. Both care.
Mating systems with male care
Eggs of dominant femaleare in center (other females leave to form other nests)
gibbon
beaver
swansFrench angelfish
Why be serially monogamous?
Mating systems with male care
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Monogamous, but by constraint
Male removal decreases RS, but not enough to explain monogamy
If RS to 1/x, male needs more than x females to be profitable (or care)
Mating systems with male care
Polygyny occurs, but is rare in birds ~8%) Females can suffer from ‘sharing’ benefits, males control needed resources
Mating systems with male care
Polygyny threshold model: similar to IFD model, females make choices regarding territory quality and monogamy vs. polygyny
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Polyandry (sequential or resource defense)
Possibly increases RS when clutch size is limited
JacanaPhalarope
can have female infanticide
Mating systems with male care
No animal illustrates behavioral flexibility as deeply as humans
Culture determines much of human behavior
Human mating strategies
Providing biological reasons for human behavior can be controversial:
Implies the behavior is innate and immutable
Humans ‘debased’, ‘on the level of other animals
Findings can be misused
Human mating strategies
EO Wilson – founder of sociobiology
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Persistence and recognition of bond (monogamous or polygamous)
Cultural universals
Big paternal investment
Long dependency period (language, tools..)
Why female care alone is not enough
Male lactation?
Cultural universals
Reassurance of paternity
Males traditionally control wealth
Penalties for adultery in women
chastity belt
Cultural universals
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Long-term pairing with paternal care
Ovulation is concealed – sex occurs often and irrespective of fertility
Both sexes are choosy (not that unusual w
animals w pair bonds)
Some enhanced sexual signals compared to apes (breast and penis size)
Humans are odd, sexually
Human mating irrespective of estrous
Estrous “hidden”, mating during pregnancy and after menopause
“Sex is fun” and “promotes bonding” does not explain
is this woman ovulating?
Why the mystery??
perineal swellings
Paternity hypothesis (Alexander and Noonan)
– mate guarding, neighbor fertilities
uncertain. Female receptivity promotes
monogamy
Infanticide hypothesis (Hrdy) – confusion
of paternity in face of infanticide. Female
receptivity promotes polygyny
Why the mystery??
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Monogamous primates are almost always concealed ovulators
However primates w/concealed o. may be monogamous or highly polygamous (harems)
Why the mystery??
Human mate choiceSimilar to other animals with biparental care, both sexes participate in choice, using mutual fitness indicators
Sexual strategies hypotheses
Males and females look for different qualities b/c they have different reproductive challenges
Male preferences Female preferences
Short term sexually accessible quick resources
low investment good genes
inc.# partners
Long term paternity certainty investment
parenting ability parenting abilitygood genes good genes
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Males look for youthfulness and child bearing/rearing capabilities
Breast size estrogen effects
.7 waist to hip ratio
Male preferences
Female preferencesFemales try to balance their preference for high T effects (better provider, defender) with low T effects (better parental care)
(T is thought to be harder to maintain due to immunosuppressive effects)
Preferences of males and females may alter with menstrual cycle
Men’s preference for women vs. cycle
Women’s preference for long-termrelationships for pill users vs. non
Women’s preference for men vs. cycle
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Q1 Q2 Q3
100
75
50
25
0
% yes
Responses to 3 questions for males and females
Menopause is found only in humans and
some whales (pilot, orca)
Why is there NS for the halting of
reproduction? (and only in females?)
Older women take on more risk for less
potential gain when reproductive
H&G tribe: Post reproductive women gather
the most food of all
Orcas have higher RS when grandmothers
present in group
Menopause is odd, too…