Duck reproduction finding
Researchers have discovered how female ducks avoid unwanted sex: counter-threaded genitals.
Ducks are one of the few known birds to have penises, says Pat Kehoe, a St. Albert waterfowl biologist with Ducks Unlimited. The ducks hold the organs inside their body and pop them out whenever they need it. "I've witnessed it, although I'm not sure I should admit that!"
Forced breeding is very common amongst ducks, Kehoe says. "If you're ever around marshes in the spring, quite often you'll see seven to eight males chasing one hen." The process is so violent the hen can be killed.
Patricia Brennan, a postdoctoral researcher at Yale University, was the first to describe the strange corkscrew-shaped penises of male ducks and the equally twisted vaginas of female ones back in 2007. Her study found that ducks that force-mated more often had longer, more twisted penises and vaginas than those that did not. Curiously, the females had vaginas that had twisted clockwise, while the males had penises that twisted counter-clockwise.
Brennan theorized that these traits were a sign of sexual conflict — an arms race between the sexes over who controlled mating. While the long penises gave the males an advantage, the complex vaginas could give the females a defence.
To test this, she and her team went to a duck farm in California and filmed Muscovy ducks as they mated. Once the male was ready to do the deed, the researchers put a glass tube over the duck's cloaca and caught the penis as it shot out (the team described the process as "explosive," taking less than a third of a second). Some of the tubes were straight; others had the same clockwise twist as the hen's vagina.
The team found that the males had no problems getting into the normal tube and depositing their sperm at the end, but were foiled almost entirely by the twisted ones, ejaculating much farther down.
They concluded that clockwise vaginas could have evolved as a defence against forced mating; their complexity caused unwanted suitors to deposit their sperm farther away from their eggs, reducing the chance of fertilization. They speculated that a hen could lower this defence for a consensual mating by relaxing certain muscles.
Brennan's theory makes sense, Kehoe says, as male ducks have only a short window of opportunity to mate with a hen before they're knocked off. "If the male can't get in there quickly and get out ... it's unlikely to be a successful mating."
This is a rare and dramatic example of sexual conflict in action, Brennan says in a press release. "Ducks are providing us with an incredible opportunity to understand the evolutionary consequences of conflict."
Touchdown for the bees
Another team of scientists has figured out how bees land upside-down.
Mandyan Srinivasan, an electrical engineer at the Queensland Brain Institute, describes his study a recent issue of the Journal of Experimental Biology.
Working at the institute's All Weather Bee Flight Facility, he and his team trained bees to land on sugar-soaked yellow circles on an adjustable platform. Once they did, the team then changed the angle of the platform and filmed the bees as they landed.
The film showed three distinct phases to the landing process. First, the bee approaches the platform at any speed. Second, it slows and eventually stops about 16 millimetres from the platform, hovering in place for about 95 milliseconds.
The last phase is determined by the angle of the landing surface. The experimenters found that the bee's backsides automatically dropped to a 60-degree angle while hovering, so if the platform's angle was less than that, they could just plop their butts on the ground.
At greater angles, the bees waited until their antennae hit the surface before grabbing it with their front legs and heaving their backs up to meet it. What's more, the bees held their antennae perpendicular to the slope in these situations, suggesting they were able to eyeball the angle using stereoscopic vision.
Srinivasan hoped to use this research to develop new flight control systems.
