Editor's Note: This article is derived from
Explorit's quarterley Science Centered Newsletter.
Using high-tech tools like video cameras and robots, scientists are learning more about the mysterious world of bird love. In particular, both the bowerbirds of Australia and the greater sage-grouse of North America have evolved intricate wooing techniques. Male bowerbirds build elaborate “bachelor pads” sometimes with trinkets like shiny coins to attract interest. Sage-grouse, on the other hand, give a live dance performance including such moves as "wing swishes" and "air sac plops" to garner favor.
Romancing with Robots:
An Interview with Gail Patricelli
On Tuesday, September 20, as part of Explorit's Cutting Edge of Science Lecture Series, animal behaviorist Gail L. Patricelli will speak about her research of these complex mating rituals. An assistant professor at UC Davis, Patricelli is interested in applying her understanding of the courtship behaviors to the conservation of these increasingly endangered species. Last month Patricelli spoke with me about how she uses robotic females in her studies and how these technological gadgets have allowed her to gain more insight into the reasons why these creatures just love to love.
How did you become interested in studying bird biology?
[Patricelli] A lot of people who study birds come to it from a lifelong love of birds. I came to it more from an interest in evolutionary biology. I’m interested in birds, too, but was more curious about how behaviors evolve.
What led you to study bird courtship specifically?
[Patricelli] I am interested in the evolution of exaggerated male traits and courtship behaviors in animals. Darwin’s theory of natural selection suggests that birds are often camouflaged to blend in with their environments. So why do some males develop extreme display traits, like the peacock’s bright feathers? Darwin suggested that males of many species developed these traits to attract females. He called this process “sexual selection.” During courtship in many species, males show off their traits and females assess and compare these traits to choose their mate.
But there’s more to courtship than just males showing off their physical traits to females. The female does not passively observe the male. There’s a complex social interaction between males and females. I study the processes where sexual selection might favor social skills, the subtle behavioral responses, in addition to the physical traits.
What makes the mating behaviors of these birds (the bowerbird and sage-grouse) so unique to study?
[Patricelli] Both species have been model species for understanding the process of sexual selection. This means that the basic groundwork for what goes on with the bowerbird and sage-grouse are already researched, so it makes it easier to get in there and look at some of the more subtle behaviors.
For example, from past research we have already established that female bowerbirds prefer to mate with males that have a large collection of blue objects and have well-built bowers. But I want to find out why their courtship behaviors are so complex.
In both bowerbirds and sage-grouse the males don’t provide any parental care. So the females are not choosing a male that has a better territory or ability to feed young. Females are basing their choice on the attractiveness of male display traits; they probably do this because these traits show off the “genetic quality” of the male.
Can you describe some of the more exciting "rituals" that you've witnessed?
[Patricelli] In the bowerbirds a female will watch while a male puffs up, struts around and makes buzzing noises. This is actually the same display he will use during fights with other males. The females respond by crouching downward slowly. I wondered about what this crouching signal meant and whether it influenced male display behaviors. Are males that adjust the intensity of their displays according to female signals more likely to succeed? I thought if I could control a female robot, then I could see how the male responds to her.
What gave you the idea to use a robot in your studies?
[Patricelli] People have wanted to do this for along time. Whenever you observe a “conversation” in nature, you want to be able to manipulate one side to see how the other side will react. For example, bird song has been recorded and played back to test how the birds respond to specific audio signals. Visual signals cannot necessarily be recorded and played back in the same way. It took a long time for the technology to catch up with the idea to have robots. In my particular study, female movements are quite simple and easy to mimic with a robot, and the timing was right with the development of the technology.
Did you build the robots yourself? How did you decide how it would work and what actions it would make?
[Patricelli] I worked with an engineer and graduate students at the University of Maryland. This engineer also designed control systems for NASA. My robot needed to be custom made since the bowerbirds are relatively small and needed to have small parts. The engineer made all the electronic parts, and I made it look like a bird with feathers and all. I ended up doing a lot of arts and crafts and taxidermy that I hadn’t planned on when I started my research.
We programmed the robotic bowerbird to have three behaviors. It looks back and forth -- this is just to make it look more natural, it crouches downward, and it fluffs up its wings, which signals that it’s ready to mate.
What types of experiments did you conduct with the robots? Were any male birds fooled by the "decoys?"
[Patricelli] I was specifically interested in looking at the impact of female crouching on male display behaviors. So, I started by manipulating the rate of crouching. Each male was tested with a robot that crouched at different rates, and we measured the differences in the male behavior. At the end of each experiment we had the robot fluff up its wings to add a touch of realism. The male bowerbirds would actually try to mate with the robot – they’re not very picky it turns out. But I would scare them off pretty quickly, since I didn’t want the males to damage the robot. We found that the males do adjust the intensity of their displays according to the signals the female sends while crouching, and that males who are more responsive to female signals, are more successful in courtship.
How is this type of research different than what had been done previously? Are you learning more about the female perspective on courtship?
[Patricelli] Yes, we were looking at the roles that females play. The female plays an active role. She’s telling the male how intensely to display. Female signals are very important. In monogamous species both males and females are choosy, the importance of interaction during courtship was better understood. Whereas, in bowerbirds, sage-grouse and other non-monogamous species, males are not choosy and so the importance of female behavior in courtship had been overlooked.
Do you have any plans for future research related to your bowerbird findings?
[Patricelli] I’m planning on addressing some of the same questions with the sage-grouse. We’re developing a robot for this study as well. Sage-grouse are so much larger, and we can put additional gadgets into the robot, like a video camera and microphones. The construction is much simpler, since we can find the parts locally through model airplane retailers. They don’t need to be custom-made like the parts for the bowerbird robots.
But in some ways, the sage-grouse robot is more complicated than the bowerbird robot. Courtship in bowerbirds takes place at the bower that the male has built, but male sage-grouse gather together to display in a big open field called a lek. So, we’ll have to put the robot out on train tracks and send her out there.
I’ll also be able to address different questions from the unique perspective of the female. For example, male sage-grouse have large vocal sacs that radiate sound. The males have the ability to aim the sound, and the females like the louder sounds. With the robots we will be able to see and hear how well the male is directing the signal to her.
How will your research aid in the conservation of these species?
[Patricelli] The sage-grouse populations are declining, and they have been considered for listing under the Endangered Species Act. They are teetering on the edge and are a species of concern, in California and across their range. We think noise in the environment, created by roads and energy development, is interfering with the courtship and mating process. My study will focus on how they use sound to communicate, and how environmental noise is interfering with their ability to communicate.
Have you learned anything that might be useful to our species (Homo sapiens) as we are out on the "lek," so to speak?
[Patricelli] Are you asking for dating advice? Well, I guess you could say that the males that come on too strong, too soon don’t do well. The males that watch for and respond to the female signals have the best success. However, the goal of my research is not provide dating advice, but it’s hard not to anthropomorphize.
Gail L. Patricelli’s talk, “Courtship in Bowerbirds and Grouse: Using Robots to Study Animal Sexual Behavior,” will take place Tuesday, September 20 at the Davis Branch Library, 315 E. 14th Street, at 7:30 p.m. The talk is free and is sponsored by Novozymes.
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