4/18/2012 9:16:00 AM
Cost-benefit analysis of parental care: Parental care needed to enhance survival of
offspring but dangers to the parents also exist (eg. Predators). Ghalambor and
Martin predicted that parent birds should adapt their parental care depending on
two factors: (1) nature of the predator- does it eat the prey or the adults? (2)
annual mortality rate of adults. If mortality is low, chances to reproduce again in
other seasons is high so adult birds should try to secure their own survival. If adult
mortality is high, adult birds should make sure their offspring survive since their
own chances of survival are limited and hence they may not be able to have
Why is maternal care more common? Perhaps,
o because females have already invested so much in an egg, they are more
inclined to make sure their offspring live.
But this theory fails with some species that lay expensive-to-make eggs
and then abandon them.
Perhaps: it is more costly for males to care for the young since all of the
young may not be his. But all of a female’s young are hers, so less costly
Male Water Bugs: eggs laid on the back of the male. He pumps up and down in the
water to keep aerated water around the eggs. Paternal care essential for egg
development in this species. Eggs are large and need a lot of oxygen. Large eggs
needed because they allow the first instar to be larger, and hence the adult insect
to be larger than other species. Why not females but males (as parent) though?
Similar to fish. Males who are brooding a clutch of eggs attract a second female.
Also, females are able to spend more time eating to increase their own size and lay
more eggs since they are not tied down to brooding. In many species, there are factors that allow a mother and young recognize each
other so that a mother doesn’t end up caring for young that are not hers.
Adoption of Genetic strangers: sometimes parents do care for young that are not
their own. It’s bad if a parent mistakenly kills their own offspring so (for example
gulls) simply feed any chicks that confidently approach them for food. But this
allows strangers to succeed too. Adoption doesn’t significantly cost the parent.AND
HENCE evolve In bluebirds, if a male joins a female which she is fertile, he will care
for the offspring. If he joins her when the fertile period is over, then the rule is “no
parental care at all.” Hence this is a strict dichotomy in some species.
Parasitism: some species lay their eggs in the nests of others (eg. Cucko