Amphibians have been referred to as the ”canary in the coal mine” because they are so susceptible to environmental pollutants. As animals that breathe through their moist skin as well as with their lungs (or gills in the tadpole stage), they become exposed internally to anything that can enter through the pores in their skin. Here at St. Olaf we have been very pleased with the large amphibian populations that have developed as a result of our wetlands restoration projects. This is an indication of the low pollution levels in our restored wetlands, undoubtedly due in part to the large native vegetation (prairie &/or woodland) planted around these wetlands. Chorusing of many species can be heard on campus starting with the Western Chorus Frog in late March to the Gray Tree Frog that is still chorusing into August.
We have documented 9 species of frogs, toads and salamanders in our wetlands. The native species that occur here are: W. Chorus Frog (Pseudacris triseriata), Gray Treefrog (Hyla versicolor), Cope’s Gray Treefrog (Hyla chrysoscelis), Northern Leopard Frog (Rana pipiens), Green Frog (Rana clamitans), Wood Frog (Rana sylvatica), American Toad (Bufo americanus), and the Tiger Salamander (Ambystoma tigrinum). Recently (2004), we documented our first non-native amphibian in our large wetland and that is the Bullfrog (Rana catesbiana). The Bullfrog is native to Wisconsin and to the Mississippi River backwaters in the most southeastern tip of Minnesota . In the past century it has been introduced in a number of Minnesota lakes and rivers, especially in the eastern part of the state.
The Spring Peeper (Pseudacris crucifer) has been identified in Rice County, but has not been identified at St. Olaf to date. It uses woodland ponds rather than prairie wetlands and could possibly move into our restorations in later years when our tree plantings become more mature.