When it comes to mallard bills, brighter is better: A bright yellow bill is duck-speak for “I’m healthy,” attracting more female ducks than dingy green ones. After discovering that avian semen has antibacterial properties, scientists then found that the semen of brighter-billed males killed more bacteria than the semen of darker-billed ones. It implies that by seeking out bright-billed males, female ducks are protecting themselves against bacteria-related sexually transmitted diseases.

In her experiment, University of Oslo researcher Melissah Rowe collected semen from ducks (a feat unto itself—the videos in this link are amazing, but watch at your own risk) of various bill colors, and then tested how well the semen killed bacteria such as E. coli. She found that ducks whose bills had more carotenoids—an organic pigment that brightens bills—also had semen that more effectively killed E. coli. However, they discovered that the semen’s effectiveness against the bacteria S. aureus wasn’t associated with bill color, possibly implying that this bacteria doesn’t pose much harm to ducks.

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Men diagnosed with erectile dysfunction probably wouldn’t be too keen to hear that they might have bigger problems, but a new study in the journal Circulation reinforces that unfortunate idea. Given that both ED and heart attacks can result from restricted arteries that prevent blood from flowing freely, doctors have long suspected that they might be connected. Now, the study says, there’s evidence that one precedes the other. From The Los Angeles Times:

The results are probably not too surprising, added Dr. Robert Kloner, a cardiologist at USC’s Keck School of Medicine, “because arteries in the penis are smaller, so atherosclerosis shows up there sooner,” perhaps three to four years before the onset of cardiovascular disease.

The take-home message, both experts said, is that when a patient seeks treatment for ED, typically from a general practitioner, he should be given a full physical work-up to look for heart disease and referred to a cardiologist.

The guidelines for treating men with ED already state that they should be examined for cardiac problems. Kloner says updated guidelines in a few years could make that recommendation more forceful, so doctors can make sure a penis attack doesn’t become a heart attack.

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Image: iStockphoto

It snowed and snowed and snowed in Britain this week, enough that many people in the country got stuck at home. But some of those people still had a good time. A Web site intended to help restless married people meet one another called IllicitEncounters.com reports a surge in new members over the last few days—more than 2,500 in the last six days—particularly from areas hit hard by the wintry weather, like Hampshire and Berkshire. From Reuters:

“In light of these figures, I’d be interested to see how much work those ‘working from home’ have actually done,” IlicitEncounters.com spokeswoman Sara Hartley said in a statement.

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As you’ve probably heard, a man’s testicles hang down because sperm are hyper-sensitive to temperature and need to be a little cooler than the inside of the body. But isn’t there more to it than that?

Oh, definitely yes, says research psychologist Jesse Bering, writing for Scientific American. Bering goes on at great length in his analysis of testicular location. Sure, he argues, the temperature part makes sense. But why would natural selection, which so rewards passing on your genes, put a man’s means of passing on those genes in such a terribly exposed place on his body?

Bering’s lengthy account of gonad geography, and the studies trying to explain it, includes some real gems:

One of the more fanciful accounts–and one ultimately discarded by the authors–is that scrotal testicles evolved in the same spirit as peacock feathers. That is to say, given the enormous disadvantage of having your entire genetic potential contained in a thin satchel of unprotected, delicate flesh and swinging several millimeters away from the rest of your body, perhaps scrotal testicles evolved as a sort of ornamental display communicating the genetic quality of the male.

Oh, and this, on how a man’s cremasteric muscle works to keep his sperm at an optimal temperature by contracting and drawing the testicles up on a cold day and relaxing when it’s hot:

[That's] why it’s generally inadvisable for men to wear tight-fitting jeans or especially snug “tighty whities”–under these restrictive conditions the testicles are shoved up against the body and artificially warmed so that the cremasteric muscle cannot do its job properly. Another reason not to wear these things is that it’s no longer 1988.

In all seriousness, there’s nothing Discoblog values more than analysis of the silly… other than over-analysis of the silly.  If you haven’t had your fill of scrotal hypotheses,  check out the rest of Bering’s post.

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Image: iStockphoto

If you thought going to the club was bad, imagine having to dance in front of potential mates for over an hour and a half, lest they will eat you. Male Australian redback spiders, members of the black widow family, pay the ultimate price if their mating dance doesn’t impress.

Here’s how it works, via Livescience.com:

Males, which are just 1 percent to 2 percent of a female’s body weight, dance about the web of a potential mate, plucking at the threads and sending out vibrations. Once the male redback has performed an adequate dance, the female will allow him to mount her and insert one of his two palps, or copulatory organs, into one of a pair of sperm storage organs. The male then somersaults to place its abdomen directly above his mate’s fangs. That’s perfect positioning for the female to begin devouring the male’s body.

To avoid being gobbled up by the female halfway through mating, males need to dance for 100 minutes, according to new research. But the dancing males better have a good internal clock. Females can’t determine the source of courtship, so if the dancer exceeds the optimal time, a slick male could sneak in a mate with the female while the dancer ends up alone on the web.

For a video of the life-or-death dance, click on over to the Discovery News.

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Image:  Ken Jones