Parental Care and Family Conflict II

Question 1

What are the two questions in sexual conflict? What are the general responses? What is the first question an example of? What is an example of amount of care?

Answer 1

1. Who should care for kids? - depends on constraints (lactation), ecological factors (predation risk, future consideration, and food), and the other parent
2. How much care should be provided? - conflict over how much care because one sex may want the other to contribute more than they want to
3. Prisoner’s dilemma
4. Male scissor-tailed sergeant fish wants to eat a few eggs to get himself through the season and female disagrees

Question 2

If both parents care for the young, can there still be conflict between them? Why or why not?

Answer 2

1. Yes
2. There is still a want to put in less work (less exertion may increase future success).

Question 3

If both parents are caring for the young, what is advantageous for each sex to do individually when the other reduces care? What is the ESS for both? What happens if the slope of best effort is greater than -1? What does this mean?

Answer 3

1. Individually = partially compensate
2. ESS = intersection between each one’s partially compensated effort given the effort of each.
3. One parent is overcompensating.
4. Either male or female will provide all of the care, ESS is not stable

Question 4

What is an example of partial compensation? What was an experiment done? What were the results? Why were these results stable when this behavior was thought to be unstable?

Answer 4

1. Great tits
2. ONE parent subjected to playback of increased begging calls for food and increased its feeding rate.
3. BOTH parents overcompensated
4. There was communication between the two parents as to how much food the nestlings overall required (and nestlings naturally begin to need more food since their feeding rate is increasing).

Question 5

What are two types of familial conflict? How do they arise?

Answer 5

1. Intrabrood conflict (between offspring) - offspring more related to themselves so gimme gimme gimme
2. Interbrood conflict (p v o) - parent may want to trim for the future but offspring want food nowwww

Question 6

Where does the offspring curve asymptote at relative to the parent? What is the cost curve caused by and what does this mean for both parent and offspring? What is the result of these curves?

Answer 6

1. Offspring asymptotes 2x the parent (because it’s 2x more related to itself)
2. Caused by reducing fitness to other siblings (either now or later). Means that cost curve is about the same for both.
3. Optimal investment for parent < optimal investment for offspring

Question 7

What is an example of inter-brood sibling rivalry? Explain. Why does mom allow this to happen (2 reasons)?

Answer 7

1. Fur seals - mom makes a lot of kids, so in good years she gets a lot and in bad years the better ones can pick off the bad kids (takes 2-3 years to wean a pup so when she has another, the older may kill the younger via starvation or attacks)
2. Insurance: in case old one dies, Extra: good years means she gets another kids

Question 8

What is an example of intra-brood sibling rivalry? Explain. What is the bottom line with this example?

Answer 8

1. Blue-footed boobies - female lays an egg, and lays another after four days (smaller neck to reach for food and older attacks when hungry, so if food is not abundant will not survive).
2. Younger chick is insurance.

Question 9

What is the difference between facultative and obligative siblicide? Why does obligative siblicide occur?

Answer 9

1. Facultative - younger is killed if food is scarce but otherwise survives

Obligate - mom only fledges a single chick but lays two eggs (one always dies)

2. Insurance :)

Question 10

How can sibling relatedness effect rivalry? What is a situation where relatedness is low? What do birds use as a signal for quality when relatedness is low? Under what circumstances does this signal not work?

Answer 10

1. The more related siblings are, the less rivalry they’ll have (inclusive fitness).
2. Lots of affairs
3. Red mouths
4. Cavity nesters (it’s dark, can’t see red mouths)

Question 11

What is an important example of sibling rivalry and parental effort? Explain. What was an experiment done on these birds and what were its results? What were the three missing elements in this scenario? Why do these elements exist?

Answer 11

1. American coot - chicks have long orange feathers when they hatch
2. Cut off feathers of 1/2 the brood = feeding of cut feathers drops dramatically (cut all = no effect)
3. 1) Kids die often (strong brood reduction) 2) Hatching asymmetry effects brood reduction (later hatchlings much more likely to die in a week) 3) After 10 days, mortality rates equalize again between older and younger chicks
4. In first 10 days, chicks are left to fend for themselves, then mom overfeeds the smallest chick to make up for leaving him (can tell who he is because he will have more orange feathers) BECAUSE OF INTRA-SPECIFIC BROOD PARASITISM where parasites are younger than her own chicks