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Upper Midwest Environmental Sciences Center

Farm ponds as critical habitats for native amphibians
A Field Guide to Amphibian Larvae and Eggs of Minnesota, Wisconsin, and Iowa
Field guide contents

Green and Mink Frogs

Green Frog Rana clamitans
Mink Frog Rana septentrionalis

Status: R. clamitans – Common in Wisconsin, Minnesota and Iowa
R. septentrionalis – Locally abundant Wisconsin and Minnesota.
Green Frog tadpole
(Green Frog tadpole) 7.4 - 10.0 cm total length
field map
R. clamitans
field map
R. septentrionalis

Green Frogs are found near springs, streams, and ponds and Mink Frogs are often found among lily pads in ponds, swamps, and streams. Adult Green Frogs superficially resemble American Bullfrogs as adults but are smaller and have dorsolateral folds along the back. Mink Frog adults can be difficult to distinguish from Green Frogs, but mature Green Frogs have bands, “tiger stripes,” on their hind legs instead of the indefinite patterns of spots and blotches found in Mink Frogs. Also, Mink Frogs emit an odor similar to rotten onions when their skin is rubbed roughly. Mink Frogs are found only in northern Minnesota and Wisconsin within our range. Mink Frog and Green Frog tadpoles are similar, although Mink Frogs have been reported to have pink-buff colored spots on their tail.

Mink Frogs lay eggs in loose globular masses (500–3,000 eggs in a mass), often in deep water (> 1 m depth). Mink Frogs need cold, well-oxygenated water for egg development because the egg jelly is thick, and they are not laid on the surface of the water as are Green Frogs and American Bullfrogs. Green Frogs lay eggs in a large floating film with up to 5,000 eggs. Green Frog and Mink Frog tadpoles have a muscular tail with low fins. The belly is completely opaque and the greenish bodies have numerous dark blotches consisting of fuzzy dots, dashes, and splotches, but not distinct round dots.

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URL: http://www.umesc.usgs.gov/terrestrial/amphibians/field_guide/green and mink frogs.html
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Page Last Modified: December 29, 2010