Something you probably haven’t put much thought into is duck sex – but it turns out the birds have a disturbing mating method.
Harvard University zoology professor, Richard O. Prum, specialises in bird studies and has written a book about the unthinkable act – with details more shocking than you’d think.
Just like their human equivalents, males need some attractive characteristics in order to seduce females.
For ducks and other birds, this means a lot of attention is focused on their plumage or feathers – but not everybody has a display worth boasting.
This means that forced copulations are ‘pervasively common in many species of ducks,’ according to the award-winning academic.
When ducks copulate, their penises regrow. Every mating season the penis starts to shrink until it’s 10 per cent of its full-grown size. Pictured is a male goosander duck swimming on the river. Pictured here is a male ruddy duck with its iconic blue beak
How females evolved to the darker side of duck mating
He even described it as socially organized ‘gang rapes’ that are ‘violent, ugly, and even deadly’, in his 2017 book.
‘Male ducks had evolved penises that would enable them to force their way into an unwilling female’s vagina,’ he wrote.
The academic claimed that this represents a ‘selfish male evolutionary strategy that is at odds with the evolutionary interests of its female victims and possibly with the evolutionary interests of the entire species’.
Fortunately, the female ducks can defend themselves using their complex anatomy – their vaginas are corkscrew-shaped, making them difficult to penetrate.
‘Females had evolved a new way – an anatomical mechanism – to counter the action of the explosive corkscrew erections of male ducks and prevent the males from fertilizing their eggs by force,’ Professor Prum explained.
This type of sexual evolution is termed antagonistic coevolution – where genitalia have evolved to keep up with threats.
Male ducks are infamous for their bizarre penises (pictured is the male ruddy duck), which are corkscrew-shaped, exceptionally long and unfurl explosively when it’s time to mate
How ducks actually mate
He also explained that, unlike 97 per cent of birds, ducks have penises – and they boast being amongst the best endowed vertebrates, if you’re measuring in terms of ratio of body to member.
When ducks copulate, their penises regrow. Every mating season the penis starts to shrink until it’s 10 per cent of its full-grown size.
It reverts to its usual size when the season is over and is stored inside the body, only coming out to mate.
Prum described the process as ‘resembling a cross between using your arm to evert a sweater sleeve that is inside out and unfurling the soft, motorised roof of a convertible sports car with a hydraulic drive’.
However, this isn’t the only oddity found in the process of duck mating. The actual penis itself spirals anticlockwise from its base to its tip.
In his book, The Evolution of Beauty: How Darwin’s Forgotten Theory of Mate Choice Shapes the Animal World — and Us, Prum wrote: ‘Like a selection of sex toys from a vending machine in a strange alien bar, duck penises come in ribbed, ridged and even toothy varieties.’
He explained that this is ‘to hook into a female’s reproductive tract’, which is as long and convoluted as the penis.
It doesn’t stop there – female duck genitalia is equally strange – full of ‘dead-end side pockets or cul-de-sacs,’ according to the professor.
Unlike their male counterparts, some spiral clockwise, the opposite direction to the anti-clockwise spiraling duck penis.
