I was sure I’d written about the wonderful subject of duck sex on Tet Zoo before. However, having searched the archives I can’t find much, which seems odd. Male ducks have large – often very, very large – penises. The text-book example is the Argentine lake duck Oxyura vittata, originally reported to have a 20-cm-long penis (McCracken 2000) (this in a bird about 40 cm long in total), but later shown to sometimes have a penis that hangs for a length of 32.5 cm but stretches to 42.5 cm when fully unwound (McCracken et al. 2001). The Argentine lake duck is a stifftail, a group of ducks that have been described as ‘promiscuous and boisterous in their sexual activity’. Perhaps the evolution of the incredible penis has been encouraged by sperm competition; the distal part of the penis in these ducks is brush-like, so it might be that they actually work to remove the sperm of other males before ejaculating their own (McCracken et al. 2001). Proportionally large penises are also present in dabbling ducks and diving ducks.
If male anatomy is remarkable, it follows that the female parts must be pretty interesting too, but because vaginas are more difficult to observe than penises (insert hilarious quip), good data on genital anatomy in female waterfowl has only become available relatively recently (Brennan et al. 2007). This work – widely reported in the popular media – showed that female genitalia in waterfowl are complex, often featuring blind alleys and complex coils. You might predict that male and female parts have co-evolved: the problem is that the vaginal coils often twist in the opposite direction to the natural coil of the penis. This led Brennan et al. (2007) to propose that the evolution of the complicated vaginal structures indicated ‘antagonistic rather than mutualistic co-evolution’ (p. 4), and that they were there to help prevent forced extra-pair copulations.
And, as you’ll know if you’ve spent any time watching ducks, ‘forced extra-pair copulations’ are very common in ducks. The Mallard Anas platyrhynchos is the best (or should that be worst?) example of the lot: females are handled so roughly by males (sometimes by groups of as many as 12 males) that it’s quite common for people to speak of witnessing ‘duck rape’, and forced copulation is a common strategy used by males of this species (Young 2005). It’s so common that there’s even a handbook telling you what to do to discourage it (The Idol Bat Guide to Stopping Duck Rape). Sometimes, female mallards are drowned [adjacent picture from Moeliker (2001); read on].
Indeed, the mallard is so, err, sexually enthusiastic that it will shag virtually anything given the chance, live or dead. I’m sure you’re familiar with Moeliker’s (2001) famous, award-winning paper ‘The first case of homosexual necrophilia in the mallard Anas platyrhynchos‘. I was well aware of that. Even I, however, was not prepared for this…
Thanks, I think, to Jason Brunet.
For other articles on sex and sexual organs see…
- Terrifying sex organs of male turtles
- Traumatic anal intercourse with a pig
- The spiny genitals and rock-chewing habits of crested porcupines
- How do you masturbate an elephant?
Refs – –
Brennan, P. L. R., Prum, R. O., McCracken, K. G., Sorenson, M. D., Wilson, R. E. & Birkhead, T. R. 2007. Coevolution of male and female genital morphology in waterfowl. PLoS ONE 2(5): e418. doi:10.1371/journal.pone.0000418
McCracken, K. G. 2000. The 20-cm spiny penis of the Argentine lake duck (Oxyura vittata). The Auk 820-825.
– ., Wilson, R. E., McCracken, P. J. & Johnson, K. P. 2001. Are ducks impressed by drakes’ display? Nature 413, 128.
Moeliker, C. W. 2001. The first case of homosexual necrophilia in the mallard Anas platyrhynchos (Aves: Anatidae). Deinsea 8, 243-247.
Young, G. 2005. Northern mallard Anas platyrhynchos. In Kear, J. & Hulme, M. (eds) Bird Families of the World: Ducks, Geese and Swans. Vol. II. Oxford University Press, pp. 513-517.