Most birds do not have penises, but there are a few exceptions. Ducks are among these exceptions, with their males sometimes displaying genital organs of quite an impressive size. However, not all duck penises are similar, and some of them tend to evolve differently from the others. Therefore, a team of ornithologists from Mount Holyoke College, Massachusetts, wanted to see what impact could the duck community have on their genitalia.
Ducks are well-known for their great sexual endowments
A duck species is the proud owner of the biggest penis per body size, the Argentine duck (Oxyura vittata). The animal has a genital organ which can reach 43 centimeters in length. Unfortunately for other ducks, not all species sport such impressive organs, thing which sparked the interest of researchers. They presumed duck society has a big influence on them, and decided to study it in connection with duck penises.
The research team focused their attention on two species, the ruddy duck and the lesser scaups. Ruddy ducks (Oxyura jamaicensis) are well-known for their big genitalia, while the others (Aythya affinis) display quite an unimpressive penis. During two breeding seasons, all ducks were split in two groups: the first one contained both male and female specimens, while the other was composed exclusively of males.
Duck penises grow longer when they face competition
The non-endowed lesser scaups proliferated in a male environment, and grew longer organs than usual. This confirmed the researchers’ expectations, where competition triggered an adaptive response. However, the situation was different for the ruddy ducks.
Some of them reached their sexual maturity only later, and others were ready for reproduction only for shorter periods than usual. This strategy was meant to reduce intense competition between specimens, and also prepared them to propagate their species in harsher conditions.
Therefore, a little competition proved beneficial for duck penises. All of the species displayed a lengthening of their sexual organ while living in an all-male community. The lengthening of lesser scaups was more visible, since their organs grew significantly. When it comes to the other ducks, their organs were already big, so it wasn’t so easy to spot a minimal grow.
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