Whether it works with the reproduction, decides the female.
Read aloud Duck females have a built-in chastity belt: They protect themselves from nuisance by unpleasant males by cramping their vagina so that the drakes can not penetrate. The US researchers have found out by testing the deformability of the penis with the help of differently shaped glass tubes: Although the drakes can inflate their penis in a flash, this is not flexible enough to adapt easily to the vagina can. So the puzzle must be solved by the duck, the scientists conclude: They assume that the female relaxes his muscles only when he has found his dream partner. Most male birds do not have a penis, but press their so-called cloaca against the female during mating. These body orifices are used to eliminate faeces and urine as well as for mating. However, ducklings also have an inwardly inverted penis, which is deployed at lightning speed during mating. Despite this great speed, the mating season does not use the genital as often as the males would. The courtship is often accompanied by struggles and sexual harassment, which the females use to protect themselves in an unusual way: they pull their vagina together, causing it to take a clockwise twisted shape, similar to a corkscrew or a wrung out towel. But the penis of the drake is turned exactly opposite to this direction.

The researchers now asked themselves the question of how it can come to mating despite these different anatomies. They made two hypotheses: either the Erpelpenis is particularly adaptable, or the females change the shape of their vagina. To check this, they first allowed the pilot to board a duck. As soon as the monkey's cloaca swelled as a sign of readiness for copulation, the scientists held differently shaped glass tubes in front of the female's cloaca. The different tubes were modeled on possible forms of the vagina: one was cylindrical, one rotated in one and another in a counterclockwise direction.

Using a high-speed camera, the scientists filmed the "mating". So they could watch as the drakes evert their 20 centimeters long penis in just 0.36 seconds. However, he was able to develop to full length only in the straight tube and in the copy whose turns corresponded to those of the penis. The conclusion of the researchers: If the penis can not adapt to the vagina, it must adapt to the penis. Accordingly, the scientists assume that the female ducks only relax their vaginal muscles and thus allow the penetration of the penis, if they agree with the drake. This theory is also supported by the fact that laying eggs would not be possible with cramped muscles.

Patricia Brennan (Yale University in New Haven) et al .: Proceedings of the Royal Society B, doi: 10.1098 / rspb.2009.2139 ddp / science.de? Jessica von Ahn ad

© science.de

Recommended Editor'S Choice