Why is the coloration of a frog considered to be protective?
Answers
By making four different models, they were able to ask two questions.
Does the bright color matter? For example, does it matter if frogs use red or yellow to warn predators?
Do birds attack models that naturally occur in the jungle more or less than models that are not naturally found within the jungle? For example, does the red model (which is found in the jungle) get attacked less than the yellow model (which is not found in the jungle)?
Answers to these questions help to us understand what color works best for warning predators.
What Does a Bird See?
The scientists also wanted to determine how birds see the bright or dull colors of frogs in the jungle. We take for granted our color vision and assume all other animals see what we see, but birds see more colors than us (Learn more at http://askabiologist.asu.edu/explore/seeing-color). Scientists use bird visual schemes to determine what birds are actually able to see and if the birds can see the different colors of Play-Doh models.
Fig 3 PLOS article
Bright colors are a great way for frogs to protect themselves and warn predators that they are poisonous. Scientists found red frogs were attacked the least compared to the black and brown frogs. Click on the figure to learn more.
Color and Novelty
Before the scientists could use the clay models, they had to demonstrate that the models were realistic and that birds think the clay models are real frogs. To do this, they used both real frogs and clay frogs and tested whether birds attacked the real frogs more than the clay models. It turns out that the clay frogs were just as likely to get attacked by predators as real live frogs, demonstrating that clay frogs work just as well as real frogs. The best part of this method is that no more real frogs need to be attacked.
More to the Story
The scientists went one step further and looked at how likely the different Play-Doh models were attacked based on how easy it is to detect the different colored models. For example, the red model is much easier to see than the black model and therefore the red model will be found by birds more often and should be attacked more than the black model. This is where the bird visual schemes are important. The researchers calculated how likely each clay model was to be attacked. The number of attacks was based on whether the model frog’s colors were different from the colors in the jungle or similar to the colors in the jungle.
What Did They Discover?
The black and brown models were attacked more than the scientists expected since the black and brown models are difficult to see against a jungle background. On the other hand, scientists expected the brightly colored models would be frequently attacked. In fact, they found the yellow and red models were not attacked as much as expected. These results demonstrated that bright coloration does decrease the risk of being attacked. They also found that the models that were natural to the environment were attacked less by birds than the novel models that were not natural to the jungle.
Tree frogs
Which frog would you be if you wanted to keep from being eaten?
Let’s return to imagining life as a frog. Which color would protect our frog selves from predators? From these experiments, we know two things. 1) Bright colors are important. 2) Bright colors that are the same as other poisonous animals are also important. So we should use either red or yellow because they are bright against a jungle background and we should all be the same color so that predators can learn and remember to not attack us. In the end, what color turns out to be the best for not being eaten? Red is the best color for our frog. At least the best color if we want to avoid being eaten in the jungle.