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Extra-pair copulation and sperm competition in the zebra finch
T R Birkhead1, J Pellatt, F M Hunter
1Department of Animal Biology, The University, Sheffield, UK.
Nature
|July 7, 1988
Summary
Extra-pair copulations (EPCs) in zebra finches can lead to paternity, with the last mating sperm having precedence. However, EPCs followed by pair copulations have a low fertilization success rate.
Area of Science:
- Animal Behavior
- Evolutionary Biology
- Reproductive Strategies
Background:
- Most bird species exhibit social monogamy.
- Despite monogamy, extra-pair copulations (EPCs) are frequent in many bird species.
- Paternity guards like mate-guarding and frequent copulation are common, yet EPCs still occur.
Purpose of the Study:
- To quantitatively estimate the fertilization success of EPCs in a monogamous passerine, the zebra finch (Poephila guttata).
- To investigate the impact of mating order on paternity when EPCs occur.
Main Methods:
- Experiments were conducted under semi-natural captive conditions.
- The study focused on the zebra finch (Poephila guttata).
- Fertilization success was assessed following EPCs and pair copulations.
Main Results:
- EPCs were confirmed to result in extra-pair paternity in zebra finches.
- Sperm from the last male to copulate demonstrated precedence in fertilizing eggs.
- A single EPC occurring last was disproportionately successful, while EPCs followed by pair copulations had low success rates.
Conclusions:
- EPCs are a significant factor in determining paternity in socially monogamous birds.
- The timing of copulations, particularly the last mating event, plays a crucial role in fertilization success.
- These findings have substantial implications for understanding sexual selection dynamics and reproductive strategies in birds.