by Whit Gibbons

November 18, 2002

Recently I received a communication about frogs that emphasizes the importance of confirming conventional wisdom and offers a metaphor for the human response to environmental degradation.

The issue started with an email from Germany. As often happens in scientific inquiry, though the answer to the question was pretty straightforward, arriving at the answer was not. But the easy way out accepting what "everyone knows" more often than not simply perpetuates misinformation. Although finding an answer that destroys an urban myth or a commonly held belief may disappoint some people, we are better off knowing the truth.

Joe Pechmann at the University of New Orleans, who is a noted amphibian conservation biologist, received a query last month that read: "I am writing a weekly column for Die Zeit, Germany's major weekly paper, on scientific urban legends that my readers ask me about. Now you surely have heard the story of the boiling frog that is often told by consultants or activists: If you put a frog in boiling water, he will try to escape. If you put him in cold water and heat it gradually, the frog will remain in place until he's boiled, because that's the lesson, to him (and consequently to us) gradual change is not perceivable. Frankly, I don't buy this. But I am looking for professional advice (and I don't want to boil frogs). Can you help me with that question? Thanks! Christoph Droesser, Hamburg, Germany"

Joe was not sure what the answer was, so he referred Mr. Droesser to me. I also passed the buck, saying: "I have heard the anecdote many times and actually heard a Baptist preacher give a sermon in Mississippi in which he used the story of a big bullfrog in a bucket of water that was being heated. The situation was presented as an example of how gradual habituation to a devilish situation leads to acceptance of an even worse one. But with a real frog in real water, my bet is that when it began to get uncomfortable the frog would jump out if it could, long before the water started to boil. Nonetheless, consultants, activists, and others who are unaware of gradual environmental problems are responding in the way we like to think a frog acts rather than the way it does."

I went on to say, "Although I do not know a data-based answer myself, I am aware of experiments that have been done on responses of amphibians to thermal conditions. In some of the experiments the temperature was gradually raised, so I feel certain someone familiar with those studies would have an impression of what a frog would do as the water warmed up. I am sending your question to Dr. Victor Hutchison at the University of Oklahoma to see what he says. I would be interested to know also."

Vic's answer was as follows: "The legend is entirely incorrect! The 'critical thermal maxima' of many species of frogs have been determined by several investigators. In this procedure, the water in which a frog is submerged is heated gradually at about 2 degrees Fahrenheit per minute. As the temperature of the water is gradually increased, the frog will eventually become more and more active in attempts to escape the heated water. If the container size and opening allow the frog to jump out, it will do so." Naturally, if the frog were not allowed to escape it would eventually begin to show signs of heat stress, muscular spasms, heat rigor, and death.

So where does that leave us with the metaphor for the human response to environmental degradation? Well the idea that you can induce a frog to remain in boiling water if you start it off in cold water is not true biologically. But that does not diminish the need to keep an eye out for the gradual relaxation of environmental laws and regulations. The metaphor lies in the frog's ability to escape from the container: if there's no way out, then the frog's fate is a foregone conclusion.

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