Subject: How can brightly coloured frogs exist?

I do not understand how natural selection can give rise to brightly coloured 
poisonous frogs. As I see it, their current natural advantage exists because 
predators have an innate sense that such colourful creatures are best avoided. 
However, for this innate fear to come about, the ancestors of today’s frogs 
must have been eaten in sufficient numbers to 'naturally select' future races 
of predators with an innate fear of bright frogs. How can the frogs' natural 
advantage be passed on, if creating that advantage means that their ancestors 
had to die in massive numbers?

Re: How can brightly coloured frogs exist?