L10

Question 1

Male mallards mate guard to prevent their female copulating with an extra-pair female, what will happen if a male cant mate guard?

Answer 1

if males cant mate guard, timing and frequency of copulation will determine who gains paternity

Question 2

Do American kestrels mate guard? How do they counter this?

Answer 2

Lack of mate guarding - so males copulate up to 690 times per clutch

Question 3

Do all behaviourally successful copulations result in sperm transfer?

Answer 3

Zebra finches = 36% of copulations fail
Chickens = 50% of copulations fail

Question 4

Why would a male not transfer sperm when he had the chance?

Answer 4

• Cape bird, antarctica
  
  • Penguins concentrated on ridges which become snow free earlier
    -Adelie penguins are monogamous sea birds
  • Reclaim previous nest sites by static display
  • Females return and pair up with previous partner if present, if not she pairs up with nearest available mate, but then re joins previous male if he arrives late
  • Lay two eggs, and an extra if one is lost
  • Incubating parent has to guard against Antarctic Skua birds
  • Chicks quickly grow and form creches whilst both parents forage food
    Parents are vulnerable to sea lions and killer whales

Question 5

Copulation in Adelie penguins

Answer 5

• Male solicits copulation by head bowing
  Researchers assessed whether insemination occurred
  -Researchers assessed whether insemination occurred

Question 6

3 possible outcomes:

Answer 6

• Ejaculate enters the female’s cloaca
  • An ejaculate misses
  • No ejaculate is seen
  • Researchers recorded outcome and caught female then examined cloacal smears to recorded sperm presence
  • If an ejaculate is missed or not seen there is no insemination
  • Observations of cloacal ejaculate is not a good contender for tract sperm presence

Question 7

Two sources of sperm competition in Adelie penguins

Answer 7

• EPCs 9.8% of females-Mate switching 14.9% of females

Question 8

How widespread is sperm competition in Adelie?

Answer 8

EPCs = 9.8% of females in successful EPCs
Either sex initiated this
Occasionally males tried to force EPC but none of these were successful

Mate switching = 14.9% of females

Question 9

Prostitution

Answer 9

-Exchanging EPCs for nest material
- Small stones form a platform for which eggs are laid on
- Inadequate platforms are likely to lose eggs by meltwater as they become wet, muddy etc
- Stones collected by both sexes
- Stones are often in demand and some attempt to steal
- Copulation in exchange for stones
- Half took second stones
- Male benefits by gaining EPC for offspring in which he doesn’t have to parental care for

Question 10

Possible benefits of prostitution behaviour

Answer 10

• Male benefits by gaining EPC for offspring in which he doesn’t have to parental care for
• Female benefits by gaining a source of stones, fertility assurance and good genes as the best males collect stones

Question 11

Females engage in EPC, so do males ensure insemination at every opportunity?

Answer 11

• Outcompete insemination from other sperm
  
  • 57 copulation attempts
  • 42 cloacal contacts
  • 25 inseminations

Question 12

Reasons for failure of pair copulations

Answer 12

-Most failures occur when male dismounts or when cloacal contact is observed but no sperm is drawn in

Question 13

Sperm limitation

Answer 13

• If males have limited semen supplies consecutive successful ejaculates take longer

Question 14

Median time elapsed between consecutive successful ejaculates

Answer 14

-Greater than time elapsed between a success and a fail

• Males increase insemination rate towards females fertilisation time

If males have limited semen, time interval would increase through pre-laying period as they run out of sperm

Overall ejaculate interval increased over pre laying period

Suggests sperm is limited in male penguins

Question 15

What might males do if sperm is limiting?

Answer 15

-Carry on copulating regardless

-Conserve sperm and allocate ejaculate strategies

Question 16

Prediction: If males allocate sperm strategically they will prioritize EPCs over pair copulations

Question 17

Collect male ejaculates experiment

Answer 17

Collect male ejaculates
* Stuffed toy
* Popular with young single males but not established breeders
* Males don’t seem to suffer from depletion

• Suggests males ejaculate sperm to female with greatest paternity return
  
  • If males allocate sperm strategically they will prioritise EPCs over pair copulations
• Successful EPCs were less likely to result in failed ejaculation whereas it was more common in pair

Males allocate ejaculate strategically

25% of male copulation attempts failed prior to cloacal contact

Males terminated fewer EPCs than pair copulations

Female terminated more EPCs than pair mountings

Question 18

By what mechanism could strategic allocation be achieved?

Answer 18

• Males attempt EPCs only when they have sperm available
  • Males withhold ejaculate from their partners to conserve sperm

Question 19

Results

Answer 19

Males ejaculated during EPCs have fewer ejaculations for paired female than males that withhold

Question 20

Do paired males gain more successful copulations than EPCs

Answer 20

Yes

Question 21

Do pair males father the chicks they raise?

Answer 21

Yes

-Only one contained extra pair offspring 2.2%

-Neither chicks were fathered by male that raised them
* Most father their offspring

Question 22

Why do they allocate sperm to EPC if they dont father their offspring

Answer 22

• Such high fitness for successful EPC
  
  • Extra pair fathers show a slight but slim success rate

Male Adelie have limited semen supplies

Withold for EPCs, but risk pair paternity

Most males raise their offspring and outcompete rival males