What is a miner's canary and why the term is used in reference to frogs?

A miner's canary refers to the use of canaries in coal mines as an early warning system for toxic gases; if the canary showed distress or died, miners knew to evacuate. The term is also applied to frogs because they are sensitive to environmental changes and pollutants, serving as indicators of ecosystem health. Thus, both canaries and frogs symbolize organisms that signal danger in their environments, highlighting their roles in monitoring ecological conditions.