So, last night I was asked how hedgehogs mate.
The obvious answer was, carefully! My interlocutor suggested that perhaps face-to-face was most likely, but as far as I know, very few species (& that short list includes our own) do that. It turns out that care is indeed needed, for the male approaches the female from behind, & she must adopt what's coyly called a 'special posture' and flatten her spines so that the sensitive portion of his anatomy doesn't take on the appearance of a kebab.
The question was actually part of a wider discussion around the architecture of sexual reproduction: the mechanics of how the bits fit. If you'd like to hear the entire thing, it's here on the RadioLive site.) Entomologists, in particular, seem to spend quite a bit of time studying this architecture, not least because these details may help them distinguish between species that are otherwise pretty much identical in their appearance. (There's a lovely story about Michael May's work on dragonflies here, complete with
In many cases the structures – which can be quite bizarre – are driven by competition. Competition between the males, but also between males and females. So in those dragonflies, for example, the males' penes have all sorts of features that are related to sperm competition – they allow a male to scoop out, scrape out, or otherwise displace semen deposited by another male, and replace it with their own. And in mallard ducks, which are highly promiscuous, a sort of male/female arms race has driven the evolution of extremely complex genital anatomy in both males & females, discussed here by Ed Yong. Incidentally, that link also includes a video – perhaps not for the faint-hearted! – of the rather explosive uncoiling of & ejaculation from the drake's corkscrew penis.
Some of these structures can be rather large: we're talking a metre long for male African elephants, for example (according to wikipedia), around 2.7m in right whales, and up to 3m in Blue whales (the largest animals alive). And as one might expect, this has been attracting human attention for a long, long time. Sadly, some of that attention has been seriously harmful to the survival of some species – witness the aphrodisiac claims made for the sex organs of tigers by Traditional Chinese Medicine, for example. But there's also the point-&-wink sort of interest, shown in a painting of a dead sperm whale dating from 1606 and described by Menno Schilthuizen in the excellent book, Nature's Nether Regions:
On an otherwise nondescript Dutch beach likes the Leviathan, its beak agape, its limp tongue touching the sand. A smattering of well-dressed seventeeth-century Dutchmen stand around the beast. Prominently located, and closest to the dead whale, stand a gentleman and his lady. With a lewd smile, face turned towards his companion, he points at the two-metre-long penis of the whale that sticks out obscenely from the corpse. Centuries of smoke-tanned varnish cannot conceal the look of bewilderment in her eyes.
These few square feet of canvas … [exemplify]… the unassailable fact (supported by millenia of bathroom graffiti, centuries of suggestive postcards, and decades of internet images) that humans find genitals endlessly fascinating.
However, it's only relatively recently that this fascination has really been reflected by scientific interest: interest in the structures, their function, and their evolutionary history. But, as Brian Switek points out in his book My Beloved Brontosaurus (which is also an excellent read), we still have no idea how dinosaurs – especially the big ones – actually mananged to mate. Particularly the big spiny ones. This may well remain one of life's not-so-little mysteries.
It has occurred to me that the search history on my computer will look really, really odd as a result of doing a spot of research for this post!