Download 18 Parental Care and Nesting

18. Paternal Care
Parental Care
• Includes all behavior directed towards
offspring
– Feeding
– Protecting
• Predators
• Elements
– Teaching
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Parental care
• Very costly behavior
– Time
– Energy
– Vulnerable to predation
emperor penguin
red shouldered hawk
earwig
tarantula hawk
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Evolution of parental care
• Bigger gametes
– Increase zygote size
– Increased survival
• More gametes
– Increase potential number of
offspring
• Females initial investment more than males
– (larger gamete size, internal development in some
animals)
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Parental Investment
• Lots of zygotes
– Little care provided
• Clutch of Offspring
– Some care provided
– Greater (longer) parental investment
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Parental Investment
• The fewer the offspring the greater the postnatal care provided; per offspring
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Parental Investment
• The fewer the offspring the greater the postnatal care provided; per offspring
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Parental Investment
• However, the smaller the embryo the greater
the number that can be produced.
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Evolution of parental care
• Females have a greater incentive to make
sure their gametic investment is not wasted.
• There females often provide the majority of
parental care.
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Evolution of parental care
• Investment on current offspring
• Increased investment = increased
probability of young surviving
– AND increased fitness for parents
• Trade off between current and future
reproduction
– Time, energy, risks spent by parent on current
offspring (parental investment)
– influence possibility of having future offspring
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Evolution of parental care
Potential tradeoff:
• More energy invested now, less energy
available for future reproductive efforts.
• Increased parental investment
can affect survival of adults.
– Potentially decreasing fitness
Parental care investment is
subject to selection.
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Life History
• Life history traits
– characteristics of an individual that influence
survival and reproduction
Age at maturity
House Mouse
2 months
African elephant
11 - 20 years
Atlantic Salmon
3-6 years
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Life History
• Life history traits
– characteristics of an individual that influence
survival and reproduction
Number of offspring
House Mouse
African elephant
Atlantic Salmon
5-8 young every month
1 calf every 3-8 years
1,500 to 8,000 eggs
once
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Life History
• Life history traits
– characteristics of an individual that influence
survival and reproduction
Number of reproductive events
House Mouse
~6-12
African elephant
Atlantic Salmon
~3-10
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(semelparous = 1)
(interoparous > 1)
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Life History
• Life history traits
– characteristics of an individual that influence
survival and reproduction
Lifespan
House Mouse
2 Years
African elephant
60-70 Years
Atlantic Salmon
3-6 Years
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Remember EPCs…
• 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.
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Opportunity for Polygyny
• 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.
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Opportunity for Polygyny
• 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.
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Predicting Male care
• In male bias systems care is more common
– Females limited by number of eggs, gestation
– so males increase success by providing care
• Female bias more
opportunities to
reproduce
– Males likelihood to
desert increases
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Bi-parental care
• Bi-parental care is common (particularly in
birds).
• In many species, males provide more care
than females.
Australian mallee
fowl
Greater rhea Seahorses
African cichlids
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Male uniparental care
• Females lay eggs, then provide no care
• Males provide care
Mouth Brooding
Nest Guarding
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Male uniparental care
• 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
– The males carry this burden
(which can exceed 50% of
the male's wet mass) until
eggs hatch
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Male uniparental care
• 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.
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Males carry eggs
glued to back
Males moisten eggs laid
out of water
No parental
care
Giant water bugs
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Caring for the right offspring
• Offspring recognition in colonial species
– Discriminating parental care
Mexican free tailed bat
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Caring for the right offspring
• Offspring
recognition in
colonial species
• Cliff swallows
can recognize
own young,
rough winged
swallows cannot
cliff swallows
colonial
barn swallows
solitary
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Caring for the right offspring
• Offspring recognition in colonial species
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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
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Optimal Threshold Model
signals you want to
accept
signals you want
to reject
acceptance errors
rejection errors
adapted from Reeve 1989, Starks 2003
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Adoption
• Intra- and Interspecific
• Parents will often care
for offspring that are
not their own
• Not resource limited
• Decrease risk to own
offspring
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Adoption
• Adoption increases survival
– If the abandoned offspring can find a foster parent
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Caring for the wrong offspring
• Brood parasites - cowbirds, cuckoos
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Caring for the wrong offspring
• Brood parasites - cowbirds, cuckoos
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shiny cowbird
bronzed cowbird
screaming
cowbird
brownheaded
cowbird
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3 species of cowbirds in northern
Argentina
bay-winged
cowbird
screaming cowbird
colonial, builds own lays eggs in nests of
nests. Egg
1 species - the bay
dumping?
winged cowbird
shiny cowbird
lays eggs in nests of
176 different species
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Brood parasitism
• Parasitism success dependent on being able to
convince host eggs are their own
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Brood parasitism
• Parasites can also remove hosts eggs to
increase care given to their own
– And ultimately survival/success.
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Brood parasitism
• Parasite can also remove competition
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Key to brood parasite success
• Size disparity important in
success of brood parasites
– Since parasite parents do
not always know when
hosts eggs were laid
– Parasite young have to be
larger at hatching, and
grow faster
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Nest/Den Construction
• Habitat Choice
– Territorial
– Safety
• Dens (or roosts) consist of preexisting structures
– Not labor intensive
• Nests are constructed
– Energetic and time costs
– Burrows & Mounds
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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)
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Sibling Conflict
• Scramble Competition
– Every mouth for
themselves
• Preferential feeding
– Largest/Healthiest eat
first (Competition)
– Hungriest eat first
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Adaptive parental strategies
masked booby
blue-footed booby
have two eggs, first
hatched chick always kills
second chick
have two eggs, often
raise two young
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Parent-offspring conflict
• Selection may act on parents and offspring
differently.
• Some actions
that increase
fitness of
offspring may
reduce fitness
of parents.
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Begging
• From offspring perspective:
– Way of attracting food
– Reflect actual needs of the
young (Honest)
– Greed (dishonest)
• From parent perspective:
– Way of identifying hungry
offspring
– Ensure offspring are being
fed enough
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Asynchronous Hatching
• Birth order can promote or reduce sibling conflict
and parental favoritism
– Synchronous hatching, all offspring born at same time
– Greater food demand
– Can reduce parental efficiency/success
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Offspring size disparity
• Typically first young will be
largest and most likely to
succeed
– Fledge
• Females can adjust by
increasing investment (larger
eggs) for later eggs produced
– Enough so that later hatchinglings
are born larger, and are able to
compete for food
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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
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Can parents control sex of offspring?
Seychelles Warbler
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Control of offspring sex
• Haplo/diploid organisms (like ants, bees and wasps)
– Fertilized egg = female ; un-fertilized egg = male
• Temperature Dependent Sex Determination (TSD)
– many reptiles
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Nest Help
• 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
voles
magpie jays
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Nest Help
• Leads to overlapping generations
•
Key step in the evolution of sociality?
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Genetics basis for mating systems /
parental care.
prairie voles
Monogamous
male parental care
meadow voles
polygymous
no male parental care
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Genetics basis for mating systems /
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.
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