From ScienceDaily:
The Dyeing Dart Frog, for example, is highly toxic and warns its predators with a bright yellow-and-black pattern.
However, new research led by scientists at the University of Bristol has revealed that the colour pattern does more than simply signal “danger.” Counterintuitively, it also works as camouflage.
…
“Certain predators have evolved tolerance of toxins that would be deadly for humans, and some individual predators may have not encountered the warning signal prey before (a dangerous mistake for the predator, but also for the frog).
…
“So, colour patterns that could be distinctive close-up, but work as camouflage from a distance, would provide a clear advantage.”
…
They found that, despite being highly conspicuous at close range, the particular colours and their arrangement allow the pattern to blend together to form background-matching camouflage when viewed from a distance.
The frog’s pattern, therefore, allows it to get the best of both worlds: high fidelity camouflage until a predator discovers it, at which point its bright, highly salient, warning signal becomes clear.
Co-author Professor Innes Cuthill from the University of Bristol added: “How many other animals use ‘distance-dependent coloration’ to balance competing evolutionary pressures is yet to be explored. Paper. (paywall) – James B. Barnett, Constantine Michalis, Nicholas E. Scott-Samuel, Innes C. Cuthill. Distance-dependent defensive coloration in the poison frogDendrobates tinctorius, Dendrobatidae. Proceedings of the National Academy of Sciences, 2018; 201800826 DOI: 10.1073/pnas.1800826115 More.
It would be very interesting to know how many camouflage skin patterns work that way—and it raises some questions too: Was the landscape always the same during the frog species’ existence? If the landscape was different, did the frog display a different coat pattern then? How many generations are needed to change a coat pattern in the case of a change in ecology? We could be on to something in terms of internal mechanisms that speed up the process.
See also: Sexual trappings (dimorphism) may increase the likelihood of extinction, not survival
and
Trout adapted from salt to fresh water in only 120 years? Well, not exactly. In short, in their original habitat, the trout were spawned in fresh water, lived in salt water, and – as adults – returned to fresh water to spawn. But having no salt water available in the new habitat, they have adapted to lifelong freshwater living. It’s a good find but these fish were already capable of living in both environments. It’s not as if they moved from lifelong salt water to lifelong fresh water.