| Macquarie University
For years, researchers studying the mating behaviour of birds have been
stymied by one question: Why would females cheat on their mate ?
especially when she has a lot to lose if her infidelity is discovered.
Macquarie University biologists Dr Simon Griffith and Dr Sarah Pryke
recently solved this long-standing puzzle and have published their
findings this week in the prestigious international journal
Science.
While most birds, like humans, form partnerships to rear their
offspring, researchers have long known they have the occasional fling. But
why they do it has previously been difficult to establish because females
are especially sensitive to being caught out and will go to great lengths
to hide their behavior from their male mates, according to Griffith.
?They have a lot to lose if caught with another male so we were
intrigued to find out why the female would run such a risk since the costs
of cheating are quite high,? he said.
As in humans, male partners play an active role in assisting a female
bird to raise her young, contributing up to 50 per cent of care involved
in incubating the eggs and feeding the offspring. A male who feels he has
been cheated on can reduce the care that he gives or even desert an
unfaithful female.
To solve the puzzle of how and why females gain from a little bit of
infidelity, Griffith and Pryke focused their attention on the Gouldian
finch, a species which they are studying in the tropical savannahs of
Northern Australia and also in captivity.
During a regular breeding season, the female Gouldian finch will
copulate two to four times a day with her partner. However when given the
opportunity in an experiment, all females willingly engaged in one
copulation with an extra-pair male, irrespective of the quality of their
own mate.
Whilst this does not appear very discerning, the important part was
what happened after that copulation, Griffith said. If the extra male was
genetically better than her own partner then, with just one copulation, he
could fertilise over 75 per cent of her eggs.
?The female is apparently able to select out genetically good sperm
from bad sperm very effectively. This means that by occasionally cheating,
she is maximizing her chances of having healthy offspring because one
copulation with good male sperm is better than 30 copulations with bad
sperm. So even a little cheating can have big benefits,? he said.
The intriguing explanation Griffith and Pryke finally confirmed in
their research was that the female finch is actually quite selective in
her infidelity ? and from a genetic standpoint, for good reason.
?Our work suggests that with this mechanism, it would pay most female
animals to cheat on their partner once or twice to insure against any
genetic incompatibility or infertility that their partner might have,?
Griffith said.
Simon Griffith and Sarah Pryke are ARC Research Fellows with the
Department of Biological Sciences.
http://www.sciencealert.com.au/news/20102308-21256.html | 