Multiple causes for the malformed frog phenomenon

Michael Lannoo, Daniel R. Sutherland, Perry Jones, Donald Rosenberry, Robert W. Klaver, David M. Hoppe, Pieter T J Johnson, Kevin B. Lunde, Charles Facemire, Joshua M. Kapfer

Research output: Chapter in Book/Report/Conference proceedingConference contribution

18 Scopus citations


Progress has been made in understanding the malformed frog problem, yet we still cannot identify with assurance specific causes of malformations at particular locations. To address this problem we assembled a team of specialists and present here results on geographic distribution, water quality, parasite infection, and morphological patterns from Minnesota malformed frog sites and reference sites. Malformed frog hotspots (> 5% malformed animals) tend to occur in a broad line from northwest to southeast across Minnesota associated with the North Central Hardwoods and Driftless Area ecoregions, and are less associated with Lake Agassiz Plain, Northern Glaciated Plain, and Western Corn Belt Plain ecoregions. Few hotspots occur in the southwestern grassland and northeastern boreal forested portions of the state. There is a tendency for hotspots to occur at ecoregion junctions. No single water quality feature correlates with hotspots. Heavy Ribeiroia infections always indicate hotspots, but lesser Ribeiroia infections may or may not. Conversely, certain hotspots show no evidence of the presence of Ribeiroia. Among reference sites, two have no evidence of Ribeiroia. The most common hindlimb malformation type was ectromelia, followed by micromelia and the presence of spongiform bone. Limb hyperextension, amelia, and polymelia were the least common malformation types. Malformed frog hotspots are typically associated with altered wetlands and any solution to the malformed frog problem must include restoring these sites.

Original languageEnglish
Title of host publicationASTM Special Technical Publication
PublisherAmerican Society for Testing and Materials
Number of pages30
StatePublished - 2003
EventMultiple Stressor Effects in Relation to Declining Amphibian Populations - Pittsburgh, PA, United States
Duration: Apr 16 2002Apr 17 2002


OtherMultiple Stressor Effects in Relation to Declining Amphibian Populations
CountryUnited States
CityPittsburgh, PA


  • Amphibian declines
  • Chemical contamination
  • Habitat alteration
  • Habitat restoration
  • Malformations
  • Parasites

ASJC Scopus subject areas

  • Engineering(all)

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    Lannoo, M., Sutherland, D. R., Jones, P., Rosenberry, D., Klaver, R. W., Hoppe, D. M., Johnson, P. T. J., Lunde, K. B., Facemire, C., & Kapfer, J. M. (2003). Multiple causes for the malformed frog phenomenon. In ASTM Special Technical Publication (1443 ed., pp. 233-262). American Society for Testing and Materials.