Funded by the Netherlands Organisation for Scientific Research (NWO-Rubicon), Martine Maan and Molly Cummings investigated Dendrobates (Oophaga) pumilio, a Panamanian poison frog with extremely diverse coloration. In some areas, these frogs are yellow with black spots, in other places they are bright orange or dark blue.
Birds
Maan and Cummings discovered that this colour variation coincides with an extreme diversity in toxicity. Among the ten investigated colour morphs, there was a 40-fold difference in toxicity. The biologists subsequently calculated how the frog colours would be perceived by birds, probably important natural enemies of these frogs. They found that the most conspicuously coloured frogs – as seen through bird eyes – were also the most toxic. Thus, birds can predict the toxicity of the frogs by looking at their colours.
Less accurate
The study also shows how important it is to know the intended audience of a colour signal. Different animal species have different visual systems, and as a result they see things differently. The researchers also estimated how colours would be seen by crabs and snakes, but for those animals the conspiciousness of the frogs was a much less accurate indicator of toxicity.
Differences in toxicity
It is not yet known how the differences in toxicity arise. The frogs obtain toxic compounds from a specialised diet of ants, mites and other small arthropods. Possibly, these prey creatures are more abundant in some places than others, leading to differences in toxicity between frogs that inhabit different areas.
NWO-Rubicon
The Rubicon program of the Netherlands Organisation for Scientific Research (NWO) provides young researchers the opportunity to conduct postdoctoral research abroad. Martine Maan used this grant to work with Molly Cummings at the University of Texas at Austin. Currently, Martine Maan is based at the University of Groningen in the Netherlands.
More information:
- Martine Maan; tel. (+31) (0)50 363 2196; m.e.maan@rug.nl
- The paper “Poison frog colors are honest signals of toxicity, particularly for bird predators” by Martine Maan & Molly Cummings appeared in Januar 2012 as an open-access article in The American Naturalist.
- The American Society of Naturalists has published a version for laymen of the article.
