Frogs and Toads
See the Paper: Presence and Absence Survey of Wetland Anurans in St. Olaf College Natural Lands
Background
Anurans are amphibians that lack a tail like frogs and toads. Globally, many populations of anurans have been declining. One third of all amphibians in the world are threatened. In Minnesota, there is concern for our populations of frogs and toads. Habitat loss through agriculture and development contributes to their decline. These amphibians make excellent “indicator species” or species that are very sensitive to environmental changes. Understanding the health of frog and toad populations in a given area can tell people a lot about the health of that environment.
The St. Olaf Natural Lands are prairie, wetland, and forest ecosystems that are complex and relatively new restorations (meaning they were previously used as agricultural land before being turned into natural areas). Surveying for the presence of species of frogs and toads in the Natural Lands can help managers assess the current needs of the restoration.
A St. Olaf student surveyed for species of frogs and toads in 2016 in order to contribute baseline data to the limited anuran data collected in the area.
The Study
Cindy Fifield (Class of 2016, B.A. Biology) surveyed five different sites that were representative of the different types of habitat in the Natural Lands. The surveys were conducted every two weeks from mid-March to mid-May. Fifield used both auditory sampling techniques and visual sampling techniques.
This study also emphasized a community science framework, with some data collected by visiting fifth graders and Principles of Ecology students.
The Findings
Based off of the most recent study in the area at the Carleton Arboretum, Fifield expected to hear the western chorus frogs (Pseudacris triseriata) and the wood frog (Rana sylvatica) start calling in late March, the leopard frog (Rana pipiens) and the spring peeper (Pseudacris crucifer) begin calling in early April, and the eastern or American toad (Anaxyrus americanus), the gray treefrog (Hyla versicolor), and Cope’s gray treefrog (Hyla chrysoscelis), begin calling in May.
Out of these seven species, Fifield only observed five. The wood frog and Cope’s gray treefrog were not present in the survey effort. This may have been due to the timing of the survey, but the results inspire future questions about Natural Lands habitat.
Relevance
Long-term baseline data on species presence is important for understanding how an ecosystem is changing over time. Different species can help indicate the condition of an environment, for example, leopard frogs populations respond quickly to restored wetlands. Knowing the relative abundances of various species can inform how habitat is managed.
Citation
Fifield, C. 2016. Presence and Absence Survey of Wetland Anurans in St. Olaf College Natural Lands. St. Olaf College Local Ecology Papers.