BIOC54H3 Chapter Notes - Chapter vary: Burying Beetle, Parental Investment, Opiliones
2 May 2018
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Ch. 9: p.257-291, p.21-25, p.53-62 3/18/2018 10:42:00 PM
COST-BENEFIT ANALYSIS OF PARENTAL CARE
• EX: songbirds
• adjust their behavior depending on 2 factors:
o nature of predator (whether it consumes nestlings or adults)
o annual mortality rate for breeding adults
• those with low adult mortality rates should minimize risk of getting
themselves killed because more chance of reproducing in future
• breeding birds with high mortality should be less concerned with
own safety because low chances of reproducing in future
Why More Care by Mothers than by Fathers?
• EX: caecilian mothers let young feed on their lipid-rich epidermis
• EX: female spiders feed young regurgitated food and later let them
cannibalize her
• EX: egg-guarding of treehoppers
• perhaps since the female has already invested so much energy in
making the eggs, they have greater incentive to ensure it is not
wasted … BUT some still do like many fish and spotted sandpipers
• those that brood have a week longer period until next egg clutch is
laid than those who do not brood
• also benefits from maternal care are likely to be greater
• costs of parental care are likely to be greater for males than
females … since males that acquire many mates are most
successful
Why Are Any Males Paternal?
• actually quite common in a number of animals especially fish
• EX: male sticklebacks are able to care for up to 10 clutches of eggs
while females only 7 (even without egg guarding)
o female unable to forage and grow (bad for species where
fecundity increases with body size)
o parental males grow more slowly but negligible
• EX: St. Peter’s fish
o brooding males pay smaller price (7 days longer between
spawnings vs. 11 days for females compared to non-parental)
find more resources at oneclass.com
find more resources at oneclass.com
o parental males able to fertilize complete clutches while
females produce fewer young in the next clutch
Why Do Male Water Bugs Do All the Work?
• in harvestmen species with male parental care, females appear to
be attracted to partners with eggs in their care so evolved via
sexual selection
• in waterbugs … clutches that are separated from the male do not
develop so male parental care is essential
• male brooding developed in response to selection for a body size
that enables a bug to take down relatively large prey in order for
large eggs to develop quickly, need access to O2 (supplied by
males)
• females need more prey to produce large clutches so because
brooding limits mobility and thus access to prey, parental care has
greater fitness costs for females than males
DISCRIMINATING PARENTAL CARE
• whether male or female provides care, would not be expected to
give care to young that is not genetically theirs
• EX: Mexican free-tailed bat mothers use vocal and olfactory signals
of pups to recognize own before letting them nurse
• EX: colonial bank swallows have highly distinctive vocalizations
while solitary rough-winged swallow not so sophisticated
o rough-winged sound much alike meaning do not need to
communicate identity to parents
Why Adopt Genetic Strangers?
• risk of mistake of not feeding or attacking and killing own offspring
so safer to feed any chick in their nest
• chicks that leave natal nests and search for adoptive parents weight
more on average than those unadopted (later died)
• brood parasites: an animal that exploits the parental care of
individuals other than its parents
find more resources at oneclass.com
find more resources at oneclass.com
• EX: cuckoo mimics an entire brood of reed warbler chicks to
deceive caregivers to bring them as much food as their own chicks
The History of Interspecific Brood Parasitism
• older, larger females select younger, smaller ones to receive their
eggs, presumably because this kind of host cannot easily prevent a
larger female from gaining access to her nest
• coots can discriminate between their own chicks and those of a
parasite IF members of their own brood hatch first
o able to learn cues of own offspring first
• parasitized females tend to bury eggs of others or keep own eggs in
the center of the nest (hatch earlier)
• gradual shift hypothesis for evolution of intraspecific parasitism
yields prediction that when intraspecific brood parasites first began
to exploit other species as host, they should’ve selected other
related species with similar nestling food requirements
• evidence that birds took advantage of members of entirely different
species (interspecific)
• unresolved issue
Why Accept A Parasite’s Egg?
• EX: reed warblers accept cuckoo eggs as their own
• risk of parasitic exploitation is low but the chance of recognition
errors is modest
• acceptance is adaptive when host is a small species unable to grasp
and remove large cowbird or cuckoo eggs
• host has 2 options: abandon clutch and build new nest and lay new
clutch (high cost) or stay put and continue brooding with parasite
• even if host can correctly remove parasite eggs, parasite parent
might come back and check and retaliate mafia hypothesis
o EX: Magpie nests from which cuckoo eggs had been removed
were predated on much more than nests with accepted eggs
• experiment: 3 conditions … warblers vs. cowbird
o cowbird eggs removed and entrance left open
o cowbird eggs not touched and entrance left open
o cowbird eggs removed but smaller entrance
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
60% of the time, stays and just takes care of the cuckoo. Evolution of communication: ex: spotted hyenas regularly engage in penis presenting and penis sniffing = cooperative interaction = evolved communication system where both parties benefit, most penis presenters are actually female! How did they evolve to have a structure that looks like the male hyena penis : still unknown. Evolutionary history occurs via changes in pre-existing traits: ex: ears of moths, sensitivity of females to bat ultrasound preceded and facilitated the evolution of ultrasonic courtship by male moths, survival function mating communication function. Sensory exploitation or the retention of ancestral traits: ex: swordtails and platyfishes possess sensory bias in favor of elongate tails . But: can be tricky to test the sensory exploitation hypothesis for the evolution of communication signals. Yes: benefits (personal access to food) outweighs costs of yelling (risk of attack)
