1. Parental Care and Investment Psychology 3107

2. Introduction In many species, eggs are lad after reproduction and the young are left to fend for themselves Parents can go make more… However, parents do care for young in varying degrees and ways in a number of species

3. A Definition Parental Investment: Anything done for the offspring that increases offspring survival, while decreasing the parents’ ability to produce additional offspring Anything done for the offspring that increases offspring survival, while decreasing the parents’ ability to produce additional offspring So there is a cost!

4. Sex Differences So, why is it then that, as a rule, females give more investment than males? Reliability of paternity Reliability of paternity Pretty obvious Gamete release Gamete release ‘my work here is done’ Association with young Association with young The females are there at birth

5. Parent Offspring Conflict If there is investment, the offspring would like it to go on forever, the parents, eventually want to have more babies OK, look at this genetically, the mother and daughter/son share.5 of their genes At some point, the mother would be better served by having another child.

6. Parent offspring conflict The conflict continues until the parental cost = 2 x the benefits to the offspring Then, it is in the best interests of the parent and the kid to have another kid show up Not just the continuation of investment, but also the amount can be a bone of contention

7. Sex Allocation ‘Shall we have girls or boys dear?’ Not as odd a question as it seems Think evolutionarily Proximate mechanisms? Stress Stress X v y sperm X v y sperm Temperature Temperature

8. Parent Offspring Conflict The second kid would be related to the mom by.5, to the other kid by.5 This is NOT in the best interests of kid no.1 It shares 1.0 of its genes with itself, only.5 with new kid The offspring are only ½ as interested in parental costs as the parent is

9. More sex allocation Low Ranking pairs may have more females, high ranking pairs have more males Example Example Zebra finches More attractive males have more males (Burley, 1981)

10. Conclusions Trivers (1974) parent offspring conflict model is an amazing thing You must think evolutionarily This stuff dovetails nicely with the stuff on mating systems