A study led by Mark E. Hauber, a professor of animal behavior at Hunter College, uses 3D printers to create mock eggs to examine the behavior of robins.
Dr. Hauber and his colleagues studied the relationship between American robins and brown-headed cowbirds, two species that have long been locked in an evolutionary arms race. The cowbird, a brood parasite, lays its own eggs in robins’ nests for the robins to incubate and raise; the robin, meanwhile, continually has to develop new techniques to distinguish its own eggs from the cowbirds' before they hatch.
To learn what these techniques are, scientists place false eggs in the nests of robins and other victims of brood parasites, observing how the birds behave.
But making a false egg isn't as easy as it sounds. For results to be replicable – a must in science – all faux eggs in a study must be exactly the same.
“Previously we had to have a lot of on hand type of work to make these eggs. We had to use plaster of Paris…. [I]t was very poorly controlled and poorly standardized,” Hauber says.
But now 3D printing promises to vastly expand the research potential. “I think the technological advance is important enough that this will serve as a model and a method for other studies,” Hauber says. “We can standardize experiments in a much more well-controlled way than possible before.”
“The most interesting thing is just that this opens the door to making standardized stimuli for these types of reports,” says Don Dearborn, an evolutionary biologist at Bates College who was not involved with the study.
Hauber's study found that, for the American robin, “color is the most important factor in rejecting the eggs."
"Subtle changes that were introduced accidentally for the plaster egg or on purpose by our 3D printing process in the 3D-printed eggs [had] no impact on the rejection [rate],” says Hauber.
The unsuspecting robins accepted all the 3D-printed eggs painted robin egg color. But they rejected 79 percent of the 3D-printed eggs painted to resemble cowbird egg color, according to the research.
Previous studies verify the importance of color in robins’ decisions to accept or reject eggs in their nests.
Dr. John Marzluff, a professor of wildlife science and ornithology at the University of Washington who was not affiliated with this study, clarifies that “it’s not as obvious as one color or another, because some species are able to recognize subtle differences and some are not.”
At the moment, there exists an information gap between the behavior of birds and the methodology used to study them. Kevin McGowan, a behavioral ecologist at Cornell University, characterized it as “it’s like we’re the parents and the birds are the teenagers and we only get a bit of the story.”
The work of Hauber and his colleagues has created a way to get more of that story through a universally replicable model. “Because of the 3D technology we can share these stimuli across the world,” says Hauber.
On an even larger scale, “I think the evolutionary arms race between predator and prey and parasite and host is becoming more and more interesting, as the world is changing and we are getting new species that are having to interact with each other,” says John Marzluff, a professor of wildlife science and ornithology at the University of Washington, who was not affiliated with this study. “These new interactions are becoming more and more important to understand.”
“This [use of 3D printers] really opens up the door to be able to create things that could be useful to research in a lot of ways,” says Dr. McGowan. “One of the nice things about the world is that there are a lot of creative people out there.”