Upper Midwest Environmental Sciences Center

ARMI - Methods
folder.gif Amphibian Research and Monitoring Initiative, Midwest Region


Study Areas

Study Areas
Locations of primary mId-level monitoring sites
  • The Inventory and Monitoring Program of the National Park Service has provided additional funding for our efforts in the latter two areas. We also have conducted surveys in the Neal Smith National Wildlife Refuge, the Mississippi National River and Recreation Area, other portions of Minnesota, Iowa, Illinois, and Wisconsin.


  • We design our sampling to maximize the area over which we can apply our results (area of inference), except when we look for specific species in specific areas (targeted searches).

  • One way we select sampling locations is to divide areas we intend to sample into standard sized cells and then randomly select cells to sample.
Example of fishnet with 25-ha cells
Voyageurs National Park divided into 25-ha cells

  • We conduct surveys by listening for calls, visually searching for animals, including using dip nets, and by looking under cover-boards according to standardized methods (Heyer et al. 1994).  We also conduct targeted searches and use minnow traps.
call visual-encounter cover-board
Surveying calling amphibians
Sampling using dip nets
Checking cover boards
  • We measure several biological, physical, and chemical variables during our surveys.

  • Together these variables describe the numbers of individual species we observe, their location, and the environmental conditions at the time.

  • During the course of our visual surveys, we evaluate animals for obvious signs of ill health and deformities.
Egg masses of wood frogs with fungus
Egg masses of wood frogs
(Rana sylvatica) with algae and fungus
Deformed northern leopard frog Deformed northern leopard frog
(Rana pipiens)
  • Mark Roth using a personal digital assistants (PDA)
    Using a PDA to record data in the field
    We record data in personal digital assistants (PDA) in the field and upload those data to computers at the end of the day.

  • Our principal method for evaluating the distributions of species is by analyzing the percent of the area we sampled that was occupied by each species (MacKenzie et al. 2002, 2003).  All ARMI regional scientists use the percent area occupied as their principal statistic in describing data from mid-level monitoring.

Approval by the Animal Care and Use Committee

  • We have obtained the review and approval of our methods by a USGS Animal Care and Use Committee.

Literature Cited

Heyer, W. R., M. A. Donnelly, R. W. McDiarmid, L. C. Hayek, and M. S. Foster. 1994. Measuring and monitoring biological diversity: standard methods for amphibians. Smithsonian Institution Press, Washington, DC.

MacKenzie, D. I., J. D. Nichols, G. B. Lachman, S. Droege, J. A. Royle, and C. A. Langtimm. 2002. Estimating site occupancy rates when detection probabilities are less than one. Ecology 83(8):2248-2255

Mackenzie, D. I., J. D. Nichols, J. E. Hines, M. G. Knutson, and A. B. Franklin. 2003. Estimating site occupancy, colonization, and local extinction when a species is detected imperfectly. Ecology 84(8):2200-2207


Page Last Modified: April 3, 2018