Penis Bones – no joke!

bacula_JMLCarnivores have ‘em. Rodents and bats have ‘em. Even many primates have ‘em. But not humans.

The baculum (penis bone) is one of the most variable bones in the mammalian skeleton – you can even ID an animal by the shape and size of that one bone. Just like with insect penises, the shapes of these reproductive structures can change quickly in evolutionary terms (Carl Zimmer writes a wonderful post looking at these shifts)
What’s its function?
Well, we’re not 100% sure yet. It may allow males to copulate before being fully, ahem, at attention. Or it may stimulate the female to ovulate. Some bacula grow spiny projections which may, like some insect penises, clear out other sperm before injecting one’s own.
Let’s not leave out the girls!

The penis and clitoris develop from the same structure. So, if the penis has a bone… does the clitoris? You bet! It’s called the os clitoridis (or baubellum).

Cold feet, warm heart

SnowyGoose

Watching this snow-covered Canada Goose (Branta canadensis) swim around an icy lake, I thought “Brr”.

The core temperature of a goose, wrapped in its fluffy down coat, is ~104° Fahrenheit. But what about those feet? They must be freezing!

In a way, they are. The feet of this goose are only ~35°. As warm blood from the body travels to the toes, it transfers heat to the blood making the return trip. By the time the blood reaches the feet, it’s cold – so cold that little heat escapes through those exposed tootsies.

When the blood moves back toward the heart, it gathers heat from blood vessels traveling toe-ward. This process, called countercurrent heat exchange, keeps the goose nice and toasty.