Wednesday, 18 September 2019

For Poison Dart Frogs, Markings Matter When It Comes to Survival An experiment found that white-striped frogs were less effective at scaring off predators than frogs with yellow stripes. Yet both populations are thriving. - via Herp Digest

By Veronique Greenwood, New York Times
Sept. 12, 2019

The fanciful colored markings of poison dart frogs are a warning to predators: If you eat me, you’ll regret it.

These tiny, colorful creatures secrete bitter toxins in their skin, and birds have come to associate their distinctive markings with danger. The frogs’ chemical defenses can cause swelling, paralysis and sometimes even death. Their markings are so distinctive that it seems any frog trying out a new look would be running a serious risk.

And yet, new markings do crop up. Dyeing poison dart frogs in one part of French Guiana usually are blue and black with yellow markings. But in the nearby Mont Grand Matoury nature preserve, they have white stripes. Scientists curious about how this alternative coloration was working out ran a series of experiments, and reported some surprising results last week in Proceedings of the National Academy of Science.

The white-striped frogs were not as effective at scaring off predators as their yellow brethren, they found. But they still managed to avoid being outcompeted by the fitter, more threatening yellow-striped frogs, perhaps in part because of their location.

The researchers began by setting out more than 2,000 clay models of frogs — some white-striped, some yellow-striped and some that were solid-colored — in both the Matoury nature preserve and in the Kaw Mountains, about 30 miles away, where a population of yellow-striped frogs lives.

When they collected the models later, they looked for gouges and scrapes that indicated a bird  attack. They expected that birds in the Matoury preserve would avoid white-striped frogs while birds in the Kaw Mountains would steer clear of the ones with yellow stripes.

They were surprised to find that this was not the case. In Matoury, the white-striped frogs were attacked most, while in the Kaw Mountains frogs of all patterns were attacked about equally.

“This had us scratching our heads,” said J.P. Lawrence, a postdoctoral researcher at the University of California, Irvine, and an author of the new paper.


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