Pause for a moment and think about what you consider beautiful in the animal world: perhaps a peacock spider’s fancy dance, vibrant hues on a mandrill’s face, or the chittering chatter of a zebra finch song.
We largely have the females of the species to thank for these.
For most animals, females use more energy in reproduction than males — not just in gestating their offspring but rearing it too.Even for those who don’t give birth to live young and raise them as mammals do, simply laying an egg requires more energy than producing sperm.
This means it’s in the female’s best interests to choose the right father — with the best genes — for her offspring.
And while she might be outwardly impressed by a prancing, colourful, noisy male, showing off his genetic prowess, his dazzling displays are not the only way she chooses a mate.
Some species have evolved hidden ways to reject unwanted sperm in cases of forced copulation, a common practice in nature.Here are a few ways females have the final say in reproduction.
Picking the prettiest
In the most straightforward type of mate choice, “pre-copulatory traits” show off one’s genetic offering.
The male bower bird seeks shiny trinkets to make the most elaborate bower, the green tree frog positions himself in the opening of a drainpipe to amplify his call into the tropical night, and peacock struts while shaking his red-carpet-ready tail.Such traits and behaviours are often framed as males attracting females, but it ultimately boils down to females choosing the male — or not.
Yet for some animals, pre-copulatory traits are a prerequisite to mating.
Ching-Wen Judy Wang of the Queensland Brain Institute measured nerve cell activity in female fruit flies as they listened to the sexy serenade of the male’s mating song.
When the male’s melody hit a particular frequency, the female’s reproductive nerve cells lit up — or, if you like, were turned on.
This, in turn, triggered nerve cells that opened the hard coverings over her reproductive tract, called her vaginal plates, and allowed the male to mount her.
