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Announcements. Parental care Very costly behavior - time - energy - vulnerable to predation. emperor penguin. red shouldered hawk. earwig. tarantula hawk. Sibling conflict Sibling aggression and siblicide Occurs when resources are variable or in short supply?

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Parental care

Very costly behavior

- time

- energy

- vulnerable to predation

emperor penguin

red shouldered hawk


tarantula hawk

Sibling conflict

Sibling aggression and siblicide

Occurs when resources are variable or in short supply?

Offspring compete for resources (they only share 50% of genes)


blue-footed booby

have two eggs, often raise two young

masked booby

have two eggs, first hatched chick always kills second chick

Parent offspring conflict (Trivers)

Selection may act on parents and offspring differently.

Some actions that increase fitness of offspring may reduce fitness of parents.

Parental favoritism

Likely occurs when resources are variable and adults have more young than they can raise (bet hedging)

Females can invest in eggs differently (even choose sex in some species).

Young can be fed preferentially.

Seychelles warbler

Parental favoritism

Honest signals of quality in offspring?

barn swallows

Asynchrony in hatching (birth order) can promote or reduce sibling conflict and parental favoritism

great egret

Can parents control sex of offspring?

Haplo / diploid organisms (like ants, bees and wasps)

fertilized egg = female ; un-fertilized egg = male

Temperature Dependant Sex Determination (TSD)

many reptiles

Helpers at the nest

In some animals, juveniles stay to help second nesting effort.

More often female juveniles.

Both direct and indirect benefits.

Direct (learning about maternal care)

Indirect (inclusive fitness by helping rear related offspring

magpie jays


Helpers at the nest

Leads to overlapping generations

Key step in the evolution of sociality?

Genetics basis for mating systems / parental care.

prairie voles

Monogamous, male parental care

meadow voles

polygynous, no male parental care

In male prairie voles, vasopressin and dopamine in the forebrain regulate affiliation between mates (bond formation).

Vasopressin receptor is expressed at higher levels in monogamous species than polygynous species.

Lim and colleagues, used a viral vector to transfer the vasopressin receptor gene from the monogamous species into the polygynous species.

With this change in a single gene, the polygynous species essentially became monogamous.