[W]hen I visited the Memphis Zoo, and saw they had tapirs, I hastened the family over to see them. Imagine my mortification. This bull tapir had an organ that was so prodigious it dragged the ground. Not only that, it had three splines, or outgrowths, that made it resemble some sort of medieval weapon, like a morning star or something. It was incredibly repulsive, and so I covered the little girls’ eyes, and whisked them away to see the 1 day old baby giraffe, who could not yet stand up of its own.
The horror! Sex in the animal world! Madness.
But that’s not my point. My point is that rodent phalli, like those at the right, are bizarre. These are from Agouti paca, a South American rodent. The illustrations are from Emmet Hooper, The Glans Penis in the Genus Proechimys and other Caviomorph Rodents (1961).
Now, repulsive is a strong word, but we’re talking some serious spines there. In the classic Sexual Selection And Animal Genitalia by William G. Eberhard, this illustration is captioned (from memory) “It is difficult to imagine that the female does not feel this moving within her.” His point being that ornamentation in male genitalia, common in mammals, reptiles and insects, serves as a means of enhancing female pleasure, and therefore increasing mating chances.
The small spines may serve several purposes. Many rodents leave hard plugs in the vagina after mating. This prevents other males from copulating with the same female. The spines may help to remove that plug. I’ve also seen papers suggesting that the spines actually scrub previous males’ sperm out of the vagina. It’s also common for many animals to mate for hours or even days. By maintaining coitus as long as possible, the male can physically prevent competitors from inseminating his chosen female. The spines may simply provide extra traction.
Inexplicably, very little is known of the wild mating habits of many of these species. That makes it hard to know for sure which, if any, of these theories is operating in any given species at any given time. So much do learn, so little time.
I’m not sure what my point is, except that I don’t talk about rodent penises nearly enough. I mean, ducks were one thing, but they don’t even have real penises. Ditto for grasshoppers. With this, we’re getting, as it were, to the meat of the issue.
Undoubtedly, more to come.