3D printing has already established itself within the scientific community. It's been used to produce tools aboard the International Space Station, replicate body parts for surgical procedures, and now it's found a new niche among biologists studying bird behavior. It turns out, 3D printers produce mighty fine eggs.
Animal behaviorists at Hunter College of the City University of New York are using 3D printers to produce eggs used in experiments that examine nesting behavior among birds. They're particularly interested in brood parasites - birds that lay their eggs in other birds' nests, for the behavior of such birds offers insight into the evolutionary arms race between species.
Successful brood parasites are well-adapted to their deceptive practice, laying eggs that resemble those whose nests they target for takeover. But the foster birds have evolved means of detecting such eggs, based on their size, shape, color, and pattern, and will cast them out of the nests when the interlopers are identified.
"Hosts of brood parasites vary widely in how they respond to parasitic eggs, and this raises lots of cool questions about egg mimicry, the visual system of birds, the ability to count, cognitive rules about similarity, and the biomechanics of picking things up," says Prof. Don Dearborn, chair of the Biology Department at Bates College, a brood parasitism expert who was not involved in the 3D printing study.
Biologists have been studying brood parasitic behavior for decades, but it was always a challenge to produce realistic eggs for use in their experiments. They tried a variety of materials, such as wood and plaster, but the eggs were expensive and time consuming to produce and a challenge to reproduce consistently.
And that's where the 3D printers come in.
The scientists from Hunter College used a 3D printer to produce model eggs based on those of the Brown-headed Cowbirds, a North American brood parasite. Some eggs were painted beige to match real cowbird eggs; other were painted blue-green to match eggs of the American robin, a typical target of cowbirds. They were able to fill the model eggs with water or gel, so that the eggs retained the weight and properties of real eggs.
Their experiments were a rousing success. The robins accepted 100% of the blue-green eggs while they rejected 79% of the beige eggs. Similar results were achieved using plaster eggs, but the 3D printed eggs are more consistent and easier to produce. And since they are based on digital models, it makes for easy sharing across scientific communities, which improves the reproducibility of experiments.
"For decades, tackling these questions has meant making your own fake eggs -- something we all find to be slow, inexact, and frustrating," says Dearborn. "This study uses 3D printing for a more nuanced and repeatable egg-making process, which in turn will allow more refined experiments on host-parasite coevolution. I'm also hopeful that this method can be extended to making thin-shelled, puncturable eggs, which would overcome another one of the constraints on these kinds of behavioral experiments."
"3D printing technology is not just in our future -- it has already revolutionized medical and basic sciences," says Mark Hauber, an animal behaviorist at Hunter College and the study's senior author. "Now it steps out into the world of wild birds, allowing standardized egg rejection experiments to be conducted throughout the world."
