29. Parental Behavior - mechanisms

Q: Which groups are NOT in

potential conflict with respect to

parental behavior?

A. Males and Females

B. Siblings

C. Parents and offspring

D. All are in potential conflict

D. All are in potential conflict

Hormones and parental care

• Maternal

Not all females care about puppies

– Only females who have just given birth.

– Does not require birthing process. - can do a c section and it can still work

– Hormonally controlled by pregnancy/lactation hormones.

Endocrine Control of Mammalian

Maternal Behavior

Hormone levels of pregnancy:

• Rising progesterone levels followed by sharp drop during

parturition (birthing).

• Rising estrogen levels

• Prolactin levels rise near parturition

– Sharply for rodents, slower for humans

• Prolactin levels stay elevated until nursing complete.

Do these hormones mediate parental care?

progesterone promotes pregnancy

progesterone goes up up up during pregnancy, and crashes and falls off so animal can give birth

prolactin= promotes lactation, low low low, and right before parturition (birthing) it shoots up

Endocrine Control of Mammalian

Maternal Behavior

Transfusion (Rosenblatt 1968, 1972)

– Blood of new rat mom transfused to nulliparous (never had

babies) female.

– Nulliparous female exhibited maternal behavior within

24hours of transfusion.

Endocrine Control of Mammalian

Maternal Behavior

Prolactin

– increases during parturition and stays elevated

through lactation

– induces mammary glands to produce milk

– Induces _________ behavior

maternal

Endocrine Control of Mammalian

Maternal Behavior

Oxytocin

– increases during parturition.

– induces uterine and vaginal contractions during parturition.

– induces milk letdown from mammary glands.

– Inject oxytocin into the brain induces maternal behavior within 1 hour in rats and sheep.

– oxytocin released during birth induces ewe-lamb _________.

imprinting

General Hormonal Profile of Female Birds

steroids and hormones stay high during courship and egg laying period, then drop, and then prolactin is high during incubation

Birds – Maternal Hormones

Prolactin- high levels associated with broodiness in all birds.

In ring doves

– E2 + Progesterone required for nest building and incubation

– _______ required for brooding and crop sac development (produces “milk”).

– Prolactin wanes by day 20 when mom stops feeding young.

Prolactin

Hormones and parental care

Paternal hormones

Prolactin differences between male mice at different stages

- Dads have prolactin too.

expectant fathers and unmated males have much lower amounts of prolactin, and goes much higher when they are fathers. role now, purely behaviorally

Paternal hormones

Prolactin high in male marmosets with infants; while testosterone is low.

important for testosterone to go down so that they are less aggressive and seeking other mates, and turn on taking care of your young

shift behavior away from fighting other males and trying to mate and shift towards taking care of young

Paternal hormones

Hormonal differences associated with becoming a father in humans.

Paternal hormones

• Fathers with lower testosterone feel greater need to respond to ________ cries.

• Fathers with lower testosterone feel more _________ to hunger cries.

hunger, sympathy

Bird paternal behavior

Roosters don't provide care- but a capon (castrated male) can become broody.

In birds with male care, nest building and incubation follow courtship and mating.

Behavior parallels with:

• Decrease in testosterone

• Increase in prolactin

In birds where males mate many times (polygynous-where dads are trying to mate all the time and provide no paternal care), no decrease in testosterone after mating and usually no paternal behavior.

Bird paternal behavior and testosterone

Testosterone inhibits care of young.

Testosterone is thought to mediate a trade-off between mating effort and parental effort.

High testosterone promotes mating effort

= attract a mate

Low testosterone promotes parental effort

= care for your kids

Testosterone and paternal care

Testosterone implanted males don’t

take care of their babies

Testosterone and paternal care

Babies of testosterone implanted

males grow slower.

Hormones and parental care

Helpers

Some birds help the breeding pair

Florida Scrub Jays

Prolactin levels correlated with amount of care

even in the helpers prolactin levels go up (just not as much as mom and dad)

in those individuals that help and those that don’t, helpers have higher levels of prolactin, even if not parents

males

females