Parenting

Front 1

PARENTAL INVESTMENT

Back 1

behaviors that increase the chances of offspring survival at the cost of the parent's ability to produce & raise other offspring.

-so parenting produces conflict b/t parents and between parents&offspring.
-ex: weaning conflict in mammals (lactating demands a lot of energy. F. cant begin setting aside energy for new babies until newborns are weened.

Front 2

EXTENT OF PRENATAL CARE VARIES GREATLY IN ANIMALS

Back 2

-one factor: complexity of organism.

-other factors (E.O. Wilson)-
1) saturated habitats
2) harsh/stressful environments
3) specialized diet
4) predation pressure

(ecological circumstances ^ )

Front 3

FISH : EXTERNAL FERT

Back 3

male provides care in 72% of cases. (same for amphibians)

Front 4

FISH: INTERNAL FERT

Back 4

female provides care in 88% of cases (same for amphibians)

Front 5

MALE CARE

Back 5

favored w/ external

Front 6

FEMALE CARE

Back 6

favored w/ internal

Front 7

SO WHATS THE PROBLEM?

Back 7

does not account for pattern in species with external fertilization and siumultaneous release of eggs by female and male sperm.

-So males just as likely to show care in external fertilization species with simultaneous gamete release and in those with egg-1st order.

Front 8

TRIVERS

Back 8

--genetic asymmetry- a parent is equally related to each of its offspring, but an offspring is twice as related to itself as to its siblings. so we should expect confclits between offspring & parents.
-all offspring will want more than their fair share of parental investment
-parents want to distrubute care evenly (maybe).

Front 9

THREE HYPOTHESES FOR THESE PATTERNS

Back 9

1) paternity certainty
2) order of gamete release
3) association

Front 10

PATERNITY CERTAINTY HYPOTHESIS

Back 10

-Ridley
-parent should care for offspring that are truly its own
-external fertilization is "before the eyes" of male (small prob: impersonators run quickly and fert. egg)
-with internal fertilization, male is never sure what happened inside repoductive tract
-female is always sure eggs are her own.

2 WEAKNESSES:
-sperm competition and cuckoldry occur in BOTH internal & external fert
-if certainty low for one mating would also be low for any additional matings a male had by not caring for first clutch (gains from additional matings may be less than gains for caring).

Front 11

ORDER OF GAMETE RELEASE HYPOTHESIS

Back 11

-Dawkins & Carlisle
-if paternal care lowers the total number of offspring one can have, might expect each partner to desert after mating, leaving care to each other.
-so which sex shows care is a matter of which is left "holding the bag" after gamete release
-with internal fertilization, female left with eggs and sperm and male can desert.
-with external fertilization, female spawns first and can leave before male deposits sperm.

Front 12

ASSOCIATION HYPOTHESIS

Back 12

-Williams
-members of one sex find selves in closer proximity to the embryos after fertilization than do members of the other sex.
-proximity predisposes them to become care giving sex if ecological circumstances favor the evolution of care
-internal fertilization species: female automatically more closely associated with embryos
-so correlation in fish
-maternal care predominates in insects & mammals


what would cause males to be in proximity?
-territoriality
-in many species, males defend areas to which females are attracted.
-if females ovipost in males' territory (as often do in fishes), a male persisting in that place will be close to offspring
-may be relatively easy for male to chase off predators while still trying to attract additional females

-so polygamous territoriality has 2 benefits:
1) gain something for paternal care
2) little lost in mating chances

Front 13

WHAT ABOUT BIPARENTAL CARE?

Back 13

-rare in insects

-bit more common in fish & mammals

-usual case in birds

Front 14

WHAT DOES A MALE MAMMAL GAIN BY BECOMING A SECOND CARE GIVER THAT OFFSETS HIS LOSS OF ADDITIONAL MATINGS?

OR, WHAT DOES A FEMALE FISH GAIN BY BECOMING A SECOND CAREGIVER THAT OFFSETS HER LOST OPPORTUNITIES TO GET MORE RESOURCES THAT SHE CAN TURN INTO EGGS?

Back 14

- for mammals biparental care usually evolves from maternal care

-but in fish, from parental care.

Front 15

FOR FISH

Back 15

-parental care usually means protection

-females would need to add protection beyond that provided by males such that increased survivorship of young would offset female's decrease in fecundity.

-only 22% of fish fams have biparental care

Front 16

FOR MAMMALS

Back 16

-males evolve as second carevgivers where they can carry some of the offspring (ex: primates:mamrosets)
or feed them (ex: wolves regurgitate meat for pups)
-unusual to see paternal mammals that only guard young
-might be higher food needs of endothermic offspring (warm-blooded, high metabolism)

Front 17

FOR BIRDS

Back 17

-almost universal biparental care

-might be high need of chicks for food
^2 birds may double the amount of food they provide, but proably could not double the amount of protection

Front 18

BYPARENTAL CARE ABSENT IN MAMMALS, ESPECIALLY HERBIVOROUS MAMMALS

DOES THIS REFLECT HTE DIFFICULTY MOST MAMMALS WOULD HAVE IN PROVIDING FOOD?

Back 18

FEMALES LACTATE
SOLVES PROBLEM
SO WHY DONT MALES LACTATE?

Front 19

CONFLICTS

Back 19

-amount of food

-duration of care

others too:
-social insects
-dispersal
-sex of offspring
-offspring survival