[ad_1]
The fancy colored marks of poisoned frogs are a warning to predators: if you eat me, you will regret it.
These tiny, colorful creatures secrete bitter toxins into their skin, and birds have come to associate their distinctive marks with danger. The chemical defenses of frogs can cause swelling, paralysis and sometimes even death. Their marks are so distinctive that it seems that any frog trying a new look would run a serious risk.
And yet, new brands are appearing. In a part of French Guiana, dart poison frogs are usually blue and black with yellow markings. But in the nearby nature reserve of Mont Grand Matoury, they have white stripes. Scientists curious to know how this alternative stain worked conducted a series of experiments and reported some surprising results last week in the Proceedings of the National Academy of Science..
They discovered that white-striped frogs were not as effective at scaring predators as their yellow brothers. But they still managed to avoid being overtaken by yellow-striped frogs, more fit, more menacing, perhaps partly because of their location.
The researchers began by exposing over 2,000 clay frog models – some with white stripes, some with yellow stripes and others with a solid color – both in the Matoury Nature Reserve and in the Kaw Mountains. about 50 km away. population of frogs with yellow stripes lives.
When they recovered the models later, they looked for scratches and scratches indicating a bird attack. They expected Matoury's birds to avoid white-striped frogs, while those in the Kaw Mountains avoided yellow-striped frogs.
They were surprised to find that this was not the case. At Matoury, white-striped frogs were the most attacked, while in the Kaw Mountains, all forms of frogs were attacked almost equally.
"It scratched our heads," said J.P. Lawrence, a postdoctoral researcher at the University of California at Irvine and author of the new article.
In hopes of gaining a better understanding of the results, the researchers trained chicks in the laboratory to associate images of white or yellow striped frogs with bitter and unpleasant worms. They found that chicks came to hate yellow-striped frogs much faster than white-striped frogs. Once they've learned to be skeptical about yellow frogs, birds are more cautious about any new color.
This corresponds to the conclusions of the forest, said Dr. Lawrence. In the Matoury Reserve, white-striped frogs were more attacked because birds had trouble learning to associate white with a negative experience. In the Kaw Mountains, however, where birds had already learned to avoid yellow-striped frogs, they were equally skeptical of white-striped newcomers. Indeed, previous research had shown that birds reacted more strongly to warm colors like yellow, orange and red; white does not make the same impression.
If white-striped frogs were not able to scare predators with their colors, were they more deadly or at least more unpleasant when they were caught?
Using a test developed by Bibiana Rojas, researcher at the University of Jyväskylä in Finland and author of the new article, researchers mixed oats with frog skin extracts and then fed them to chickens. They found that white-striped frogs were less harmful than yellows. White-striped frogs seemed to go bankrupt in almost every way that mattered to survive the ravages of natural selection.
Yet, they have a healthy, living population. The researchers estimate that at least two factors are at play: the two frog populations do not seem to be in contact, judging by the limited genetic data. If they lived together, the white frogs would probably be outmatched. But as they do not, the fact that yellow-striped frogs are more successful has no effect on the survival of white-striped frogs. As long as their gene pools do not mix, even a less well-fitting version can survive.
The other factor is to remember that appearance is not everything. While the team was picking up frogs in the forest, they noticed an essential difference.
"When you meet one of those yellow-striped frogs, they're right in the middle of the forest," said Dr. Lawrence. "They do not care at all about your presence. Frogs with white stripes, they are much more secretive, much more nervous. You often have to dive into a burrow to catch one.
By changing their behavior, white-striped frogs may have increased their chances of success. Even in the ruthless natural world, where only the strongest are supposed to survive, a new counterintuitive innovation may persist under the right circumstances.
[ad_2]
Source link