They act like sponges for toxins and pollutants. Frequently these substances, even in minute concentrations, have deleterious effects on reproduction. Some scientists believe that the decline in amphibian populations and a twenty-year decline in human sperm counts may have a common cause. Frog populations are easy to monitor. Every spring, volunteers traverse the roads of Wisconsin, visiting ponds and counting the numbers of singing frogs.
Salamanders are small, secretive, nocturnal and silent.
This makes them very difficult to locate - much less count. Because of this, the International Union for the Conservation of Nature has assigned a high priority to the development of salamander population monitoring methods. In response, the Milwaukee County Zoo is beginning a study of blue-spotted salamander populations on Zoo grounds. Our Zoo is an urban oasis to many species of wildlife including the blue-spotted salamander. Long-term population studies of these animals are almost nonexistent and the best method to conduct such a study remains unknown.