here are several yellow male toads (Incilius luetkenii, I'm not sure) who turn their bodies randomly among the dead leaves:

it looks like a natural scene-except for the faint red and blue wires behind them.

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in fact, all these toads are fakes. Biologist Daniel Mennill et al made the toads using a 3D printing mechanism and painted them carefully. They also add motors to fake toads so that they can move a little bit at will.

every breeding season, the male of the toad species turns eye-catching lemon yellow, while the female remains brownish gray, and these models are made to figure out the role of bright yellow.

in the past, researchers have shown that male discoloration helps them identify females during a short breeding period, when they used a self-made clay toad model. And now they want to know if females prefer bright colors. This time, the rough clay toad seemed to be insufficient. So they made 3D printed toads and painted them in different colors. Next, as long as you wait until the right time, you can go to the natural environment to observe the female's reaction.

(the previous generation of clay toads look like this. In fact, this is not the only example of biologists deceiving animals with 3D printing. For example, there are also biologists who use 3D printing to produce simulated bird eggs of various sizes and colors. Some birds lay their eggs in the nests of other species. Researchers use fake eggs to simulate this situation to see how birds can distinguish and deal with the situation. The researcher also published 3D printed files of different sizes of eggs, so that colleagues can also make their own.

3D printing models are much more standardized than hand-made models, and it is also easy to control variables such as size and color. It feels that with 3D printing, scientists no longer have to worry about the lack of manual technology.

Source and screenshot source: http://www.sciencemag.org/news/2018/04/here-s-what-happens-when-you-replace-toads-and-turtles-3d-printed-replicas-wild