Why do ducks have big d..ks?

A post-doctoral researcher at Yale University, Dr. Brennan, has recently made some interesting findings in her studies on duck genitalia. The observations have both answered and raised questions about the co-evolution of waterfowl species, particularly, ducks.

The findings of Dr. Brennan’s study, published in this month’s journal, PLoS One, give us a better understanding of not just the mating practices of ducks, but also the physiological aspect and how it relates to the co-evolution of sexes in these species. For example, of 16 species of ducks and geese caught, Dr. Brennan found that the size of the male phallus was matched to fit the size of the female oviduct. As Dr. Brennan put it “When you dissected one of the birds, it was really easy to predict what the other sex was going to look like.”

What was fresh in this area of study is that Dr. Brennan examined the female anatomy of waterfowl, an area that has been overlooked. Through the study of the female genitalia, Dr. Brennan was able to observe that not only did the female genitalia range in size and shape, as their counterpart male, but that females are capable of expelling male sperm, perhaps as a defense when they are forced to mate, as is the case often. This argument comes from “studies on some species that have found that forced matings make up about a third of all matings. Yet only 3 percent of the offspring are the result of forced matings. ‘To me, it means these females are successful with this strategy,’” said Dr. Brennan.

This article is very interesting and sheds light on the co-evolution of waterfowl species. The findings from the proceeding study also raises questions such as, “Why does the male phallus return and disappear every year?” This is a great read for any ornithologist!

--contributed by Danny Tovar