Though glass frogs are tiny in size, research done on these amphibians has led to enormous findings: an entirely new form of camouflage.
Previously, scientists had assumed that the glass frog’s see-through skin had something to do with camouflage, but no one had pursued any experimental studies to determine its exact ecological importance.
When James Barnett went to Ecuador for a lab field trip in 2019, he was interested in spotting some of these frogs — he had done previous research on them as part of his PhD at the University of Bristol beginning in 2014. Now based at McMaster University, Barnett realized that no scientist had actually done a study to determine why these amphibians have transparent skin and how it works.
The more he looked into these frogs, the less they seemed transparent. Instead, Barnett says he found they demonstrated a subtly different mechanism — one associated with translucency rather than transparency.
“The gradient of translucency from the frog’s legs towards the more opaque centre of the body means the relative contrast of the outline of the animal to the background is lessened,” Barnett explains. “That smooth gradient means there is not a highly salient contrast boundary which your eyes would be very sensitive to.”
This gradient translucency highlights a completely different form of camouflage called edge diffusion, he says.
Alongside making the edges of the frog less of a stark contrast to the leaf, this camouflage mechanism also involves adapting to different light conditions to match the colour of their surroundings. These green frogs change in brightness and luminance at the same time the leaf does, Barnett explains.
Understanding how and why these glass frogs use camouflage to survive should be studied through the eyes of a predator, like a bird or a snake, says David Green, a professor at McGill University and Barnett’s post-doctorate professor from 2015 to 2017.
“These frogs aren’t trying to hide from us. We’re not predators,” Green says. “We tend to interpret the world as if it was designed for people, but it isn’t. We have to take ourselves out of the equation and think through other eyes in order to figure out what’s going on.”
Seeing the world through a predator’s eyes is what Barnett aimed to do, alongside his supervisor, Professor Nick Scott-Samuel. A series of experiments were conducted, both in the wild and in a lab, to determine exactly how edge diffusion works.