1. Mating Systems Psychology 3107

2. Introduction For the most part, males’ involvement in mating, well, ends after the mating Females pay for the mating a lot more Physiologically Physiologically Post birth/hatch care Post birth/hatch care Therefore, we should expect Polygyny where males have more than one mate Male variance > female variance Male variance > female variance

3. Polygyny There are several theories about polygyny Resource defense polygyny Male defends some good resource Male defends some good resource Example, hummingbirds The resource is some nectar giving flower

4. Hummingbirds Male sets up territory Excludes other males Basically, the male exchanges letting females feed in exchange for copulations Sort of like nuptial gifts in some sinsects, but the ‘gift’ is stationary Females then set up breeding territory withing male’s teritorry

5. Polygyny Threshold Polygyny may occur when the ‘polygyny threshold’ is crossed Example here is migratory songbirds Males arrive, set up territories Males arrive, set up territories Females choose mates Females choose mates

6. Polygyny Threshold When differences in qualities of available territories crosses the polygyny threshold, then polygyny results It is more profitable for the female to become a secondary female with a high end male, then a primary femle with a mid range It is more profitable for the female to become a secondary female with a high end male, then a primary femle with a mid range

7. What about monogamy Monogamy should happen if: Curves are far apart Curves are far apart Curves are flat Curves are flat In other words, little variation in quality of males and their territories Verner and Wilson did a really cool study that looked at these ideas

8. Verner and Wilson Marsh birds Quality varies greatly Quality varies greatly vs vs Non Marsh birds Not so much variation Not so much variation Prediction is that there should be much more monogamy in non marsh living songbirds

9. So, what happened Marsh species  44 % are polygynous Non Marsh  2 % are polygynous You can also get female defense polygyny Males basically guard the females Males basically guard the females Good example here is in Bison Good example here is in Bison

10. But you said we’d talk about monogamy… OK, OK…… When should mongamy happen? When the young are in need of lots of parental care When the young are in need of lots of parental care When Territories or resources are poor When Territories or resources are poor When females actually enforce it! When females actually enforce it! Some ‘monogamous’ species aren’t…..

11. Extra Pair Copulations Happens a lot in birds Ummm, happens a lot in people ‘sperm competition’ Usually when female is unguarded or when male can get away with it….. Usually when female is unguarded or when male can get away with it….. Sperm Wars Sperm Wars

12. Polyandry One female, many males Exceedingly rare Usually only happens when there is complete sex role reversal Sea horses Sea horses Spotted sandpipers Spotted sandpipers

13. Conclusions Many theories as to why different animals have different mating systems Polygyny is by far the most common When you think about it, the system correlates nicely with the gametes!