Lecture 8 - research seminar - Adelie penguins

Question 1

what happens if males cant mate guard?

Answer 1

timing and frequency of copulation will determine who gains paternity

Question 2

what can be studies to determine copulation frequency?

Answer 2

cloacal contact

Question 3

how do American kestrels mate?

Answer 3

• 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

Question 4

do all copulations result in sperm transfer?

Answer 4

• no all behaviourally successful copulation result in sperm transfer - making them invalid
• zebra finches = 36% of copulations fail
• chickens - 50% copulations fail

Question 5

what was the basis of the adelie penguin study?

Answer 5

• they carry out up to 57 copulations but not all are successful and they wanted to know why

Question 6

where was the study carried out?

Answer 6

cape bird - Antarctica - 300,000 penguins breed here - the nest on ridges

Question 7

describe the breeding strategy of the penguins

Answer 7

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

Question 8

describe parental investment of the penguins

Answer 8

• 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

Question 9

what happens when the chick is 2-3 weeks old

Answer 9

the chicks need more food so both parents go out to hunt and all the chicks huddle together in a creche

Question 10

explain the field work for the experiment

Answer 10

• 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

Question 11

what were the 3 possible outcomes after the observed copulations?

Answer 11

1) an ejaculate enters the females cloaca
2) An ejaculate misses
3) No ejaculate is seen

Question 12

how did they examine the sperm?

Answer 12

• 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

Question 13

what are 2 sources of sperm competition in adelie penguins

Answer 13

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%

Question 14

which sex initiated EPCs?

Answer 14

it was demonstrated that either sex would initate epcs however forced epcs by males were never successful - the females had control

Question 15

describe prositution in the adelies

Answer 15

• 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

Question 16

half of copulation attempts end in failure what are 6reasons for this?

Answer 16

1) no sperm deposited
2) sperm missed cloaca
3) male dismounts
4) male falls off
5) female throws male off
6) disturbed by neighbour

Question 17

in nearly 1/4 of copulation the male doesnt ejaculate what is a predicted reason for this?

Answer 17

limited semen supplies - this was proven by overall ejaculate increasing in the time before breeding season i.e. sperm is limited

Question 18

2 strategies males will limied sperm might do?

Answer 18

1) carry on copulating regardless

2) conserve sperm and allocate ejaculates strategically

Question 19

why do adelie penguins have limited time to replenish sperm?

Answer 19

there is no night time when other birds such as zebra finches would normally replenish sperm

Question 20

what was the main prediction of the experiment for males with limited sperm supplies?

Answer 20

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

Question 21

by what mechanisms can strategic allocation be achieved?

Answer 21

1) males attempt EPCs only when they have sperm available

2) males withhold ejaculates from their partners to conserve sperm

Question 22

what do the results from the investigation show about strategic allocation?

Answer 22

• 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

Question 23

do pair males father the chicks they raise?

Answer 23

• adelies are synchronus breeders - so EPCs have to take place during breeding season - could risk paternity of pairs offspring
• results showed paired males gained statistically more success in copulations and higher frequency in them
• proves that increased frequency of copulations ub the pairs does make up for EPCs
• still worth it for the male to have a go at gaining an EPC because they are still able to outcompete rival males by copulating more than them