In duck socialization, size does matter

Graphic by Kinsey Ratzman ’21

Graphic by Kinsey Ratzman ’21


Patricia Brennan, a visiting lecturer of biological sciences at Mount Holyoke, is a “basic scientist,” meaning she does research to provide knowledge on previously unexplored topics. She has spent her life studying the genital evolution in vertebrates. 

Of Brennan’s many research projects, one in particular has caused quite a splash: her research in duck genitalia. Brennan started on this subject as a post-doctoral researcher in 2005 and has recently made a breakthrough that garnered national attention.

Male ducks, who are among the 3% of birds who have penises, grow them each breeding cycle. According to an article about Brennan’s work that was published in National Geographic on Sept. 20, their penises can grow“nearly as long as the rest of their bodies.”  What Brennan discovered next is thatducks’ social scenes have a huge impact on the size of their long corkscrew-shaped penises. After receiving federal funding for her research in 2005, Brennan and her team began a research project based at the University of Sheffield (UK) and Yale University. 

Brennan set up two separate living conditions for each of the male duck types: lesser scaups and ruddy ducks. One was with pairs of females and the other with two or three males to one female. She found that the scaups, which mate early in the season and develop strong pair bonds with their mates, grew longer penises when in competition for reproduction. Ruddy ducks, who aggressively mate with females, took turns growing their penises so they were reproductively ready at different times throughout the breeding season. 

Brennan also found that although female ducks are often unwilling participants in reproductive acts, they have evolved vaginal morphology that actually protects them from being inseminated by the males against their will. The penises spiral counterclockwise and the females’ vaginas spiral clockwise with blind pockets that prevent full eversion of the male. Brennan explained in an article for The Scientist, “If the female is receptive to a male’s advances, contractions in the oviduct open up the lumen to allow the penis to bypass the barriers.”  

After the results of her study were made public, Brennan was thrown into some unexpected media attention. Fox News ran a poll with the title “Was duck penis study an appropriate use of taxpayer money?” The poll revealed that 89% of people said “No - what a quack!” 

“The whole experience was pretty horrible,” Brennan said about the poll. “My research was always viewed positively by the press and public, so to be suddenly attacked was really difficult.” 

Because Brennan is a basic scientist, the research that she does may not be immediately useful or answer a specific question, but it is important in the long run. Brennan explained, it is the foundation on which applied science, the science that answers specific questions, is built. 

As Brennan explains in The Encyclopedia of Evolutionary Biology,  “The percent of gross domestic product the U.S.A. invests in research and development has been steadily declining over the past few years.” 

This drop in funds available for research and development has disproportionately affected the funds available for basic research which mostly occurs at universities.

Brennan attended a panel discussion about defending scientific grants against unjustified attacks during the 40th American Association for the Advancement of Science (AAAS) Forum on Science and Technology Policy held in Washington D.C. in May 2015. There she discussed her experience and defended the importance of basic science. 

“If we don’t respond to these attacks, we miss an opportunity to educate people,” she said. Now, Brennan is investigating genital evolution in dolphins and sharks, and continues to teach about the importance of basic science.