1. Parental Care Patterns How much care to provide?
Who should provide care?
When should care be terminated?
Who should receive care?

2. Insect parental care

3. Distribution of parental care in vertebrates
Teleost fishes = 21% of families show PC
61% have male parental care
Amphibians = 71% show PC
50:50 maternal:paternal
Birds = 100% show PC
Usually biparental, sometimes one sex
Mammals = 100% show PC
Usually maternal, sometimes biparental

4. How much care to provide?
Parental investment: “any investment by the parent in an individual offspring that increases the offspring’s chance of surviving at the cost of the parent’s ability to invest in other offspring (Trivers 1972)
Costs of parental care include
Reduced future survival
Reduced mating opportunities

5. Parental investment changes

6. Parental care decreases survival in willow tits

7. Parental care decreases mating opportunities
A female-biased sex ratio increases the cost of brood care for males
because parental care detracts from mating

8. Alternative hypotheses for providing care
Confidence of paternity
Expect parent with highest certainty to be parental
Order of gamete release
First to deposit gametes can desert
Association
Sex nearest to offspring when care is needed

9. Parental care in fishes and frogs

10. Alternative hypotheses for providing care: evidence
Confidence of paternity (fish and herps)
Internal fertilization - 86% maternal care
External fertilization - 70% paternal care
Order of gamete release
Simultaneous fertilization (most species) - 78% paternal
Other species - male deposits first, but doesn’t leave
Association
Territorial males have external fertilization

11. Why male parental care?
Randall’s jawfish
Mallee fowl

12. Growth, fecundity and paternal care

13. Parental care can cost females more than males
Mouthbrooding results in weight loss due to reduction in feeding,
and the cost of brood care is higher in females than males

14. Parent-offspring conflict

15. Parent-offspring conflict
Wallaby conflict
Assume fixed total resource that can be used to feed offspring
Parents want to distribute resource equitably to all n offspring
Offspring want more than 1/n but not all since they are related to siblings
Difference between parent and offspring optimum increases as relatedness decreases

16. Parent-offspring conflict: how much care to provide
Parent is equally related
to all offspring, but
offspring are less related
to sibs than themselves.
Assuming full siblings,
i.e. r = 1/2
B - measured in +units of RS of current offspring
C - measured in - units of RS of future offspring B
C/2
Max. inclusive fitness
for offspring C
Benefit or
cost to
parent
Max. inclusive fitness
for parent
Level of parental investment

17. Begging loudness increases as relatedness within nest decreases
Brown-headed cowbird

18. Parent-offspring conflict: time of weaning
(Full-sibs)
(Half-sibs)

19. Parental investment and maternal age
If reproductive value declines
with maternal age, then older
females should be willing to
expend more on parental care

20. Who should receive care?
Concorde fallacy: past investment should not determine future investment - only prospects for future success
Expect parents to use honest indicators of offspring quality to allocate care

21. Sibling competition

22. Sibling conflict

23. Chick color affects parental feeding in mixed broods of coots
Control broods were unaltered
(orange) or had orange feathers
trimmed (black)
Experimental broods had
1/2 orange, 1/2 black chicks
Chick color likely indicates
offspring health