Flashcards in Lecture 8 - research seminar - Adelie penguins Deck (23)
what happens if males cant mate guard?
timing and frequency of copulation will determine who gains paternity
what can be studies to determine copulation frequency?
how do American kestrels mate?
- the males fail to mate guard due to a large proportion of their time being spent hunting
- to compensate for this the males copulate up to 690 times per clutch
do all copulations result in sperm transfer?
- no all behaviourally successful copulation result in sperm transfer - making them invalid
- zebra finches = 36% of copulations fail
- chickens - 50% copulations fail
what was the basis of the adelie penguin study?
- they carry out up to 57 copulations but not all are successful and they wanted to know why
where was the study carried out?
cape bird - Antarctica - 300,000 penguins breed here - the nest on ridges
describe the breeding strategy of the penguins
socially monogamous sea birds - the males set up the nest first and when the females arrive they up with their partners from the previous year
- the female lays 2 eggs and will lay a 3rd if one is lost
describe parental investment of the penguins
- both of them protect the nest from predators such as the antarctic Skua
- they swap turns incubating for a period of days while the other hunts
- once this chick is born they swap daily bringing krill to the nest
what happens when the chick is 2-3 weeks old
the chicks need more food so both parents go out to hunt and all the chicks huddle together in a creche
explain the field work for the experiment
- they observed about 50 pairs copulations (roughly 10,000 copulations throughout the breeding season)
- each copulation attempt and outcome was recorded
- can observe the ejaculate on the females cloaca - the females rhythmically contract their cloaca therefore you are able to record a successful sperm transfer
what were the 3 possible outcomes after the observed copulations?
1) an ejaculate enters the females cloaca
2) An ejaculate misses
3) No ejaculate is seen
how did they examine the sperm?
- examined cloacal smears from females of each of the 3 categories
- stained sperm to head fluoresced
- look under fluorescent microscope to record presence of absence of sperm
what are 2 sources of sperm competition in adelie penguins
1) extra pair copulations - 9.8% of females took part in this
2) mate switching - copulates with single male and then switches to a male that she is paired with and will help her raise her chick - 14.9%
which sex initiated EPCs?
it was demonstrated that either sex would initate epcs however forced epcs by males were never successful - the females had control
describe prositution in the adelies
- some females would exchange epcs for nest material
- they build their nests from stones which are in great demand
- males benefit by giving stones because they can father extra offspring they dont need to care for
- females benefit by a source of stones and fertility assurance
half of copulation attempts end in failure what are 6reasons for this?
1) no sperm deposited
2) sperm missed cloaca
3) male dismounts
4) male falls off
5) female throws male off
6) disturbed by neighbour
in nearly 1/4 of copulation the male doesnt ejaculate what is a predicted reason for this?
limited semen supplies - this was proven by overall ejaculate increasing in the time before breeding season i.e. sperm is limited
2 strategies males will limied sperm might do?
1) carry on copulating regardless
2) conserve sperm and allocate ejaculates strategically
why do adelie penguins have limited time to replenish sperm?
there is no night time when other birds such as zebra finches would normally replenish sperm
what was the main prediction of the experiment for males with limited sperm supplies?
if males allocate sperm strategically they will prioritise EPCs over pair copulations - this is because males arent guaranteed another EPC but they can copulate multiple times with their partner
by what mechanisms can strategic allocation be achieved?
1) males attempt EPCs only when they have sperm available
2) males withhold ejaculates from their partners to conserve sperm
what do the results from the investigation show about strategic allocation?
- males strategically allocate ejaculates to EPCs
- males that engage in EPCs had fewer cloacal contacts
- males are withholding ejaculates from their partner and strategically allocating to EPCs