Announcements Test Results for Exam 2 are in! Behavior movie tonight at 7pm in Evert 151

Mean = 41 Exam 2 Results

tarantula hawk red shouldered hawk emperor penguin Parental care Very costly behavior - time - energy - vulnerable to predation earwig

Types of investment protection from predation protection from elements provisioning - feeding, host tarantula hawk emperor penguin red shouldered hawk earwig

Females initial investment more than males (larger gamete size, internal development in some animals) Do females have a greater incentive to make sure their initial investment is not wasted? If so, females should provide the majority of parental care. Bigger gametes (increase zygote size and survival) More gametes (increase potential number of offspring)

Time, energy, risks spent by parent on current offspring (parental investment) can influence possibility of having future offspring. Investment on current offspring Increased investment = increased probability of young surviving = increased fitness for parents Trade off between current and future reproduction?

Potential tradeoff: More energy invested now, less energy available for future reproductive efforts. Increased parental investment can affect survival of adults. (potentially decreasing fitness) Therefore, each increment of parental care is subject to selection. cichlid - St. Peter’s fish

Life history traits – characteristics of an individual that influence survival and reproduction Age at maturity years 3-6 years Atlantic Salmon African elephant 2 months House Mouse

Life history traits – characteristics of an individual that influence survival and reproduction Atlantic Salmon African elephant House Mouse 1 calf every 3-8 years 1,500 to 8,000 eggs once 5-8 young every month Number of offspring produced

Life history traits – characteristics of an individual that influence survival and reproduction Atlantic Salmon African elephant House Mouse Number of reproductive events ~ ~6-12 (semelparous = 1)(interoparous > 1)

Life history traits – characteristics of an individual that influence survival and reproduction Atlantic Salmon African elephant House Mouse Lifespan years3-6 years ~2 years

Parental care should be proportional to probability offspring are yours. Females can be quite confident of maternity, males (when females mate multiply) are less confident of paternity. - cost / benefit ratio for parenting different between sexes Remember EPCs…

Variance in reproductive success usually greater for males than females (for example in polygynous, lekking species). Times spent caring for offspring = less time getting more mates. The potential reproductive rate is greater for males than females, -cost / benefit ratio for parenting different between sexes Cost of parental care is greater for males.

Operational Sex ratio (ratio of sexually receptive males to receptive females at any time) Females limited by number of eggs, gestation, so ratio often male biased. cichlid - St. Peter’s fish

However, bi-parental care is common (particularly in birds). In many species, males provide more care than females.

African cichlidsAustralian mallee fowl seahorsesgreater rhea

A female (left) and male (right) Solenosteira macrospira. The male's shell is covered with numerous egg cases After mating, females deposit egg cases on their mate's shell, and the males carry this burden (which can exceed 50% of the male's wet mass) until the eggs hatch

Giant water bugs (Belostomatidae) Large bugs, eggs also larger than typical aquatic insect. Need to exchange gases (CO2 out, O2 in) which is easier out of water.

Giant water bugs no parental care males moisten eggs laid out of water males carry eggs glued to back

Are these really the exceptions to the rule? If males help rear young, fitness increases through increased young survival. Parental care is driven by the distribution of resources, operational sex ratio, previous investment, ecological conditions…

Caring for the right offspring. Offspring recognition in colonial species Mexican free tailed bat

Caring for the right offspring. Offspring recognition in colonial species colonial cliff swallows solitary rough winged cliff swallows Cliff swallows can recognize own young, rough winged swallows cannot

Caring for the right offspring. Offspring recognition in colonial species colonial cliff swallows solitary rough winged cliff swallows

Caring for the wrong offspring It is not worth making a mistake and not caring for your own offspring! (recognition systems are not perfect) Communal care of offspring common in some species that live in groups. dwarf mongoose

Optimal Threshold Model adapted from Reeve 1989, Starks 2003 signals you want to accept signals you want to reject acceptance errors rejection errors

Caring for the wrong offspring - the extreme Brood parasites - cowbirds, cuckoos

Caring for the wrong offspring - the extreme Brood parasites - cowbirds, cuckoos

screaming cowbird brown-headed cowbird bronzed cowbirdshiny cowbird

screaming cowbirdbay-winged cowbirdshiny cowbird lays eggs in nests of 176 species lays eggs in nests of 1 species - the bay winged cowbird colonial, builds own nests. Egg dumping? 3 species of cowbirds in northern Argentina

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)

Galapagos masked booby have two eggs, first hatched chick always kills second chick blue-footed booby have two eggs, often raise two young

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? Seychelles Warbler

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 voles

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 becoming monogamous.