Which sex cares? Sexual conflict Parent-offspring conflict Parental investment

What is parental care? building of nests or burrows production of large, yolked eggs care of eggs inside or outside parent provisioning and defense of young care after independence

Parental investment Benefit Cost Fitness benefit or cost Days of care

e.g., trade-off between caring for self versus offspring Visits per nestling Nectar LowMediumHigh Parental investment = how much parental care reduces parents future fitness Palestine sunbird Markman, S., B. Pinshow, and J. Wright The manipulation of food resources reveals sex-specific trade-offs between parental self-feeding and offspring care. Proc. R. Soc. Lond. B (2002) 269, 1931–1938

Which sex cares?

Marsh Wren Mean Number of Offspring Females: Without male help 2.95 With male help3.53 Males: 1 female (helping) females (no help) females (no help)12.80 Leonard, M.L Polygyny in marsh wrens: asynchronous settlement as an alternative to the Polygyny Threshold Model. Am. Nat. 136: Sexual Conflict

Best strategy may differ for males versus females Valera F, Hoi H & Schleicher B (1997) Egg burial in penduline tits, Remit pendulinus: Its role in mate desertion and female polyandry. Behav Ecol 8: = ESS problem

Parent-offspring conflict Benefit (to parent) Cost Fitness benefit or cost Days of care Benefit (to self)

Parent-offspring conflict Comparative evidence from begging displays

Get-away pens Confined pens (farrowing crates) P-O Conflict in Pigs Pajor, E.A Parent-offspring conflict and its implications for maternal housing systems in domestic pigs. PhD thesis, McGill University.

Confined: piglets do better 1) nurse more 2) heavier 3) grow faster Get-away: mother does better 1) nurses less frequently 2) interval to oestrus shorter 3) lower weight loss