Lecture 4: parental care and mating systems Flashcards
reproductive potential of males and females
- males have higher reproductive potential than females
- due to isogamy
- M limited by access females
- F limited by resources
F dispersion dependent on
resource dispersion (food, shelter etc) but when males care then females should also be interested in dispersion of males
M dispersion dependent on
F location
when Male parental care oversees that of females what happens to reproductive potential
females may be higher than males
sex role depends on _____, which in turn depends on relative provision of parental care
potential reproductive rate
-Clutton-Brock & Vincent 1991
__% of bird species have biparental care
81% (Cockburn 2006)
obligate monogamy =
both parents essential for successful reproduction
conditions for obligate monogamy
- parents must forage a long way from nest (i.e seabirds (puffin))
- parents have specialised caring roles (i.e amazon parrots)
hornbills & monogamy
females seals herself into nest
- complete moult of flight feathers
- female and chick depend on male for all food for up to 137 days
- BUT if male doesn’t return F will eat chick
extra pair paternity is low / high in obligate monogamy
LOW
obligate monogamy: interests of parents are alinged, so in general, conflict between parents is
REDUCED
2 types of monogamy
obligate & facultative
facultative monogamy =
male care is not essential, although it usually increases productivity, so monogamy is facultative
experiment to see effect of facultative monogamy
removal experiments
if male desertion reduces reproductive success to 1/x when is it still worthwhile for hi to desert
when he can get > x partners
males prefer polyandry / polygyny?
polygyny
lions, gorillas, red deer etc
why do females agree to polygyny>
- no cost to females
- –> no male care & females settle in relation to resources & other females
- costly BUT have no choice
- benefits outweight the costs (polygyny threshold model)
polygyny: when females have no choice WHEN
–when female biased population e.g. marsh wren 1M : 1.5F
– or when deceived by males e.g. pied flycatcher M once F lays eggs leaves to find new F then abandons her and goes back to primary F
polygyny threshold model
benefits to f in polygyyny outweigh the costs
- quality of male or territory
- F choose polygyny if difference in quality exceeds polygyny threshold (diff between Monogamy & polygyny)
is there any evidence for polygyny threshold model?
good genes? little evidence
better resources? some evidence e.g. Great Reed Warbler F visit 3-11 paired / un-paired males, sometimes chosed paired
–NS diff between Monog, primary and secondary reproductive success of females
why do males agree to polyandry?cooperative polyandry
- cooperative polyandry -> when M coop in raising brood
- –> increased productivity from more paternal care outweighs costs of shared paternity
- e.g. Galapagos Hawk
- 1F : 1-8M
2 forms of polyandry
cooperative polyandry
sequential polyandry
sequential polyandry
males have little choice
=females lays series of clutches for multiple males,; males provide care
WHY? male biased sex ratio
-abundant good & precocious chicks allows uniparental care
-MALES this time are stuck in ‘Cruel bind’
what determines intensity of conflict in mating systems
- life history constraints: how much care is needed?
- ecological differences: distribution & abundance of resources?
- social conflicts: individuals try to maximise RS at partners expense
in facultative, polygyny & polyandry there is likely to be __
conflict over the preferred mating system
