Fighting Females and Caring Males: Sara Lipshutz Studies Birds That Challenge Our Binary Expectations

Sara Lipshutz
Sara Lipshutz is a new assistant professor in the Department of Biology. (Gordon Oliver, edited by Shaun King/Trinity Communications)

Be honest: when asked to think about an animal ready to fight for its territory, bearing weapons, testosterone coursing through its veins, what comes to mind? A roaring lion, mane flowing in the wind? An elk, antlers lowered in a menacing pose? Or a female bird?

For Sara Lipshutz, new assistant professor in the Department of Biology, the answer is obviously the latter. She gets why it’s not a common thought, though.

“As scientists, we're shaped by the culture that we live in,” she says. “And there's this binary expectation of what females and males should do. We expect males to fight and be aggressive, and we expect females to be caring. I'm really interested in systems that challenge that binary.”

One such system, and the center of Lipshutz’s research, is the jacana. Perched atop long slim legs and huge feet, jacanas are wetland birds native to Central America. Females are polyandrous, which means that they mate with multiple males. They breed in fresh water, building nests on the shore or on mats of floating vegetation.

Males care for these nests and the eggs they contain while the much larger females wander around defending their mates and offspring. The better she fights, the more eggs she can lay in her mates’ nests, and the more chicks survive.

“She's kind of a fighting machine,” says Lipshutz.

With animal fights often come animal weapons. In addition to their beaks and claws, female jacanas have wing spurs — spiky protuberances that crown the top of their wings.

Pair of wattled jacanas
Wattled jacanas, one of Lipshutz’ study systems, are aquatic birds whose females fight to defend territories and males care for the nests. (Evan Buck)

“They're really sharp points, and they're very bright yellow,” says Lipshutz. “They use them to signal to each other, but they also use them in fights, almost like a sword.”

One of Lipshutz’s findings is that the size of these spurs, and therefore the females’ potential to look intimidating and inflict damage, correlates to how much testosterone they have.

“There's this misconception that testosterone is a male hormone, but we can study variation in testosterone in females and link it to important traits, like weaponry or behavioral aggression,” she says.

“Recognizing that we all come in with potential biases, and then actually doing the work to test whether they are upheld, or potentially coming up with new conceptual frameworks and new methods, makes science more interesting.”

Coming to Duke after a Ph.D. at the University of Tennessee and a postdoctoral appointment at Indiana University, Lipshutz hopes to dig deeper into the evolution of female competition from a developmental standpoint.

“Jacanas are the queens of social polyandry,” she says. There are more males than females in a population, and females are much larger than males, averaging 150 grams to the males’ 90.

“I’m interested in how you build an aggressive female,” says Lipshutz. She explains that jacana chicks hatch from their eggs looking identical, but, at some point in their development, females become much larger than males. "What are the mechanisms promoting that growth?,” she asks.

“I'm also curious about how a female becomes territorial,” she says. “Is this something related to age or body size? Or is it something else?”

To answer these questions, Lipshutz goes from the macro during field work in Panama — looking at the entire bird population to understand the behaviors underlying its dynamics — all the way to the cellular level, in the lab, looking at the endocrine, physiological and genetic underpinnings of these females’ behavior and reproductive success.

“It's fun to be a muddy boots field biologist who also gets to do this kind of pristine molecular lab work,” she says.

Lipshutz also hopes to gain a better understanding of what effect we humans are having on bird populations. Along with collaborators, she was recently awarded funding to study the effect of light and noise pollution on the reproductive behavior and physiology of six songbird species in New Mexico.

“I think of myself as a basic researcher, but we're in a changing world,” she says. “I really like that I can work on a project that has conservation implications.”

Lipshutz will also take her excitement about genetics and evolution into the classroom, teaching students how genes can get passed along generations and how small changes in their frequencies can lead to the evolution of something different.

“It's a really awesome way to introduce students to the processes that generate and maintain diversity,” she says.

When Lipshutz taught the subject during a previous position as an assistant professor at Loyola University, she got a little help from another evolutionary geneticist: Professor of Biology and former Interim Dean of the Trinity College of Arts & Sciences Mohamed Noor.

“I used Mohamed Noor’s teaching materials before I even knew about Duke being in my life,” Lipshutz says. “It's kind of a dream to be able to teach that.”