The unusually long penis is probably part of a reproductive strategy designed to increase the male Argentine duck's success in a highly competitive environment. Stiff-tail ducks are promiscuous, said McCracken, and Argentine lake ducks are particularly so.
Although information on their mating habits is limited, researchers know that the courtship displays to attract femalesand fend off other malesare elaborate, vigorous, and typically performed in the presence of other ducks. There is very little pair-bonding between males and females, and the female ducks are often resistant to mating.
"Our best guess is that the birds use [the long penis] as a kind of lasso," McCracken said. "The males have to chase the females, and even during copulation the females are trying to escape."
McCracken and his colleagues don't discount the idea that sexual selectionfemale preference for a longer penishas played a role in the development of the Argentine duck's very long penis. They think it is more likely, however, the result of limited access to females, intense sperm competition, and the need for male dominance over females.
Special Tongue Muscles
Anthony Herrel of the University of Antwerp, Belgium, is co-author of the report on the chameleon's tongue and its special muscles. He believes the organ may have become specialized so that chameleons, who sit and wait for food, can maximize limited mealtime opportunities by capturing not only insects but also prey as large as birds.
In studies of two chameleon species, Chameleo calyptratus and Chameleo oustaletti, Herrel and his colleagues positioned crickets at various distances from the chameleons' jaws. The chameleons were about 12 centimeters (4.7 inches) long and the prey was placed from 5 to 30 centimeters away.
The chameleons generated enough strength in their tongues to snatch the prey and snap their tongues back, which would be quite a feat for normal muscles. The action was possible, the researchers found, because the chameleons' tongue muscles have unusual filaments that allow "super-contraction."
The unique muscle mechanism has been observed in insects, but this is the first time it's been found in a vertebrate, according to the researchers.
A chameleon's tongue doesn't poke from the reptile's mouth but is ejected with a strong force as though spring-loaded. Because the action is less powerful when the prey is closer, chameleons sometimes back up before releasing the tongue to generate the intense force needed to snatch a meal.
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