Frogs have been mysteriously dying, which scientists liken to the proverbial canary in a coal mine. They're often considered a signal of a habitat's health. Martinez steps back into the car with Deitz. According to Martinez, they are surveying under some of the worst conditions. The lack of rain over the past month is probably one of the main reasons they have not heard any calls.
Frogs are more likely to be out calling when it is warm and wet.
Scientists have long considered amphibians as early indicators of environmental problems because they live on land and in water. Most amphibians have permeable skin, which allows substances to be absorbed and concentrate in their bodies. Declines have been attributed to a variety of causes, including habitat destruction, chemical contamination, changes in the ozone layer, acid rain, parasites, and viruses. Yet not all amphibians are in decline, and within a single location, some species may be in decline while others are stable. Amphibian populations tend to fluctuate a lot.