The mink frog (Lithobates septentrionalis), sometimes called the “frog of the north,” is a 1½ - to 3-inch greenish frog with irregular spots mottled along the back and hind legs. It is often confused with the green frog (Lithobates clamitans melanota), but often lacks a dorsal ridge and the webbing on the toes of hind feet extends to the last joint on the 4th toe and to the tip of the 5th toe. The most conspicuous identifying characteristic is the strong “rotten onion” smell when handled. They are mostly restricted to cold water ponds and wetlands north of the 43° latitude. Threats include mortality or reduced fitness from contaminants, mortality and decreased fitness from disease (i.e. ranavirus, chytrid), and disturbance and degradation of habitat from increased temperatures or droughts. It is listed as a Species of Greatest Conservation Need in all six states in BCR 14.
Cold-water lakes, ponds, stream edges, springs, and peatlands of northern regions with cold, oxygen-rich water is required for embryo development. Being almost completely aquatic, they prefer shallow, permanent water with lily pads (Nymphaea sp.) and pickerelweed (Pontedaria cordata). Feeding on aquatic invertebrates is common around aquatic vegetation far from shore. Eggs are deposited on submerged vegetation. Beaver (Castor canadensis) activity appears to have a positive effect on mink frog habitat by converting terrestrial to wetland habitat and creating more landscape heterogeneity.
Habitat Management Practices
- Avoid wetland crossing with logging equipment.
- Maintain buffers around water bodies.
- Avoid altering hydrology (e.g. beaver dam removal), especially during winter when frogs are hibernating in aquatic environments.
Megyesy, J. and M. Marchand. 2015. Mink Frog. Pages A44-A48 in the New Hampshire Wildlife Action Plan, NH Fish & Game Department, Concord, NH.
Popescu, V. D. and J. P. Gibbs. 2009. Interactions between climate, beaver activity, and pond occupancy by the cold‐adapted mink frog in New York State, USA. Biological Conservation. 142:2059‐2068.
Stockwell, S. S. 1999. Mink frog. Pages 107‐110 in Hunter, M. L. Jr., A. J. Calhoun, and M. McCollough, editors. Maine amphibians and reptiles. The University of Maine Press, Orono, Maine, USA.