Michigan Department of Natural Resources Wildlife Division - Natural Heritage Program

P.O. Box 30180, Lansing, MI 48909
Coordinator: Lori Sargent, Natural Heritage Specialist


Background and Purpose
Michigan is home to 13 native species of anurans (frogs and toads). In recent years, many observers have been concerned with the apparent rarity, decline, and/or population die-offs of several of these species. This concern was not only for the species themselves, but also for the ecosystems on which they depend. Frogs and toads, like many other aquatic organisms are sensitive to changes in water quality and adjacent land use practices, and their populations undoubtedly serve as an index to environmental quality.

As a result, the Michigan Frog and Toad Survey was initiated in 1988 on a limited basis to increase our knowledge of anuran abundance and distribution, and to monitor populations over the long term. Over the next few years, a statewide system of permanent survey routes will be developed. Each route will consist of ten wetland sites which will be visited three times annually -- in early spring, late spring, and summer -- by a volunteer observer. At each site, the observer will identify the species present on the basis of their breeding season calls or songs, and make a simple estimate of abundance for each species, using a call index value of 1, 2, or 3. Miscellaneous observations can also be made from locations other than the permanent survey routes.

This cooperative survey is modeled after the very successful Wisconsin Frog and Toad Survey, which began in 1981. Over the years, the Michigan Frog and Toad Survey will provide a wealth of information on the status of Michigan frog and toad populations, and help monitor the quality of our environment.


  1. Determine a route consisting of 10 wetland sites. All sites must be easily accessible at night, preferably along roadsides. Avoid sites that require trespass on private lands. The route should extend no more than approximately 35 miles, and may be quite short (for example, your route may be contained within a particular State Game Area or city). Stops should be a minimum of 1/2 mile apart. You should not be able to hear the same individual frogs or toads from 2 different sites. Stay within county boundaries, if convenient.

    It is best to scout the area during or just prior to the breeding season to determine wetland suitability. Try to include a variety of wetland types that represents the range of breeding sites available. Consider large vs. small, open vs. shrubby vs. wooded, stagnant vs. flowing, permanent vs. temporary, natural vs. artificial, and remote vs. agricultural vs. urban sites. See the Wetland Types sheet included with these instructions for definitions. Do not avoid ponds that dry up during the year, for they are often productive during spring. Do avoid swift streams, and deep or denuded shores of lakes. Also, avoid areas with heavy background noise, such as busy streets or highways, certain industrial sites, and farms with barking dogs.

    Participants sometimes find that one or more of the sites originally chosen turn out to be unsuitable breeding habitat or are poor sites because of unforeseen background noise, access problems, etc. In these cases, it is usually necessary to replace the problem site with a new site sometime after the first survey run, thus voiding the first year's monitoring data. To avoid this, it is recommended that you begin with 11 or 12 sites for the first year and choose only the 10 most reliable sites for the permanent route. At the end of the first year, report results only for the 10 permanent sites. However, wetland breeding sites for amphibians come and go. It is expected that some sites will be better over time (i.e., beavers put in a new pond), and others will disappear (i.e., construction of a new mini-mall). These are to be expected, and the stops should not be changed to incorporate new sites or eliminate sites that are no longer available.

    If you want to run more than one route, please feel free to do so. However, if you cannot complete all three surveys on each route, select one route on which to make all three surveys and cover the other routes if you have time. Information from the additional sites will be useful as incidental information.

  2. Describe your route. Prior to, or early the first year the route is run, send us the locations of your sites clearly marked on a map. If you do not have access to a county map or other suitable map which can be photocopied, contact the Wildlife Division. Carefully mark the precise locations of your 10 sites on the maps, being sure that the marks you make are not so large as to make the location of the site unclear. Describe each listening point and wetland on the Survey Route Description Form. Describe the wetlands using the terms defined on the Wetland Types sheet enclosed with these instructions. Sites should be numbered in a convenient route sequence. Return the map route description before conducting your surveys to make sure your route is not overlapping someone else's. A route number will be assigned to your route. Return your completed data forms by 1 September of the same year.
  3. Enlist one or more additional observers who will become familiar with the route and survey procedures, and who can run the route in the event that you are temporarily or permanently unable to do so.


  1. Review the instructional material and data forms. You will receive a packet of materials that includes a cover letter, instructions, survey route description form (2 copies), field data sheets (2 copies), miscellaneous observations form (1 copy), natural history information, a tape of frog and toad calls, and an addressed envelope in which to return the data forms at the end of the year.
  2. Know the calls, phenology, and general ranges of Michigan anurans. All cooperators are required to have a cassette tape or other recording that includes the calls of all Michigan's anurans. The first cassette sent to an observer will be at no charge but there will be a nominal fee for subsequent tapes.

    New and experienced observers will find it both helpful to review the tape periodically and to take it along during surveys to help identify uncertain calls. New observers can learn the calls gradually by starting with those species that may be calling during the early spring survey period (wood frog, spring peeper, leopard frog, chorus frog, and pickerel frog), followed by those that begin calling in late spring (American toad, Fowler's toad, cricket frog, and both tree frogs), and finally those species that begin calling during the summer (mink frog, green frog, and bullfrog). It is highly recommended that new observers practice distinguishing calls in the field with the help of a more experienced observer.

    Your instructional materials also include a natural history packet which summarizes the geographic range, status, calls, biology, and morphology of each species in Michigan. Use this information to help determine which species are likely to occur in a given region, habitat, and season. Although it is entirely possible that, for example, you may find an unusually early or late singer, or a breeding population outside a species' previously documented range, you should be aware that these unusual occurrences may require special scrutiny or verification.

  3. Run the route three times, once during each designated period. The timing of the survey with the phenology of frog calling is essential. In most areas, failing to make one of the three survey runs or failing to survey all ten sites will severely limit or invalidate the entire year's data for monitoring purposes. Consider minimum air temperatures, especially for the early spring survey period, before running your route. When deciding whether or not to conduct a survey, consider the air temperature first. If air temperature is not approaching the minimum suggested temperature, wait until it does, even if it is past the recommended date. The recommended dates below serve as a guideline. Weather conditions determine good surveying time better than dates. There are different sampling dates for southern and northern Michigan (table 1).
  4. Table 1.
    Survey PeriodRange of DatesMinimum Air Temperature
    South ZoneNorth Zone
    1. Early Spring1-20 April10-30 April45°F
    2. Late Spring1-20 May10-30 May55°F
    3. Summer1-20 June10-30 June65°F

  5. Run surveys after dark, under favorable conditions. Choose an evening when air temperatures are above the minimums stated above and when wind is less than 8 mph. Warm, cloudy evenings with little or no wind and high humidity (even drizzle) are ideal. Humidity and cloud cover are not critical, but temperature is. A sudden drop in air temperature will cause most anurans to cease calling. If part way through a survey run you find that conditions deteriorate significantly (e.g., rain begins, temperature drops, or wind increases), stop the survey and complete it at the next possible opportunity, within 2-3 days if possible.
  6. Listen for calls at each site. Approach a listening point so as to cause minimal disturbance. The arrival of a car or a person may cause frogs to stop calling for a short time. Listen for a minimum of 3-5 minutes after the frogs start calling again, up to 10 minutes if necessary, to be certain of all calls. Listen to all calls audible from your listening point, not just those emanating from a particular pond, one side of the road, etc. Some calls may be drowned out by others, especially by the full chorus of spring peepers or chorus frogs. Where you suspect this to be the case, and after carefully listening and recording your initial data, you may try to silence the chorus by make a loud noise with horn, car door, or voice. Then listen for the less conspicuous species as the calling gradually resumes.

    A tape recorder will enable you to record questionable situations that can be listened to and confirmed at a later time or date. Prescription hearing aids are helpful for listeners who have volume or frequency impairment.

  7. Record your observations on the field data sheet. Include county, date, route number, observers' names and addresses, weather conditions, time and additional comments on noise levels, attempts to silence loud choruses, changes in habitat since previous visits, etc. At each site, record the call index value for each species heard, according to the following:
  8. Call Index Value Criteria
    1     Individuals can be counted. There is space between calls.
    2     Calls of individuals can be distinguished but there is some overlapping of calls.
    3     Full chorus. Calls are constant, continuous, and overlapping.

  9. Verify records of rare species and those that are outside their documented range. We encourage you to verify records for the cricket frog if you have any doubts about your identification. For species outside their range (not including the occasional undocumented county within the heart of the range), verification is also encouraged. Verification can be accomplished by: a) making a tape recording of the frog(s) in question, b) obtaining verification from 2 additional experienced observers, or c) making a good quality photograph(s) of the animal such that identifying characteristics are visible. Submit tapes and photographs with your data sheets and maps at the end of the summer.

    Taking a specimen should be considered a last resort and is not encouraged, especially for the cricket frog.

  10. Return all materials by 1 September, but keep one copy of the field data sheet for your records.
  11. Important! Maintain one or more alternate observers whom you feel will be able to produce results comparable to yours, should you not be able to run the survey temporarily or permanently. The alternate(s) should accompany you on the survey periodically and be familiar with the calls, route, and procedure.

Contributing Miscellaneous Observations
Other sight or sound observations of anurans or other reptiles and amphibians should be submitted on the Miscellaneous Observations Form. If you wish to run non-permanent survey routes of several wetlands in an area, you may submit the data on a separate copy of the Field Data Sheet, along with a clear description of the locality of each site.

Recommendations for Future Improvements
Your evaluation of the materials and procedures would be greatly appreciated. The first year of this survey was established as a pilot project in order to work out as many potential problems as possible prior to opening the survey to general public participation. Field forms, survey periods, procedures, and natural history information have been closely patterned after the Wisconsin program, often with only essential changes having been made. The idea was not to reinvent the wheel, but simply to modify it to our needs.

If you have any questions, please don't hesitate to call:
    Lori Sargent
        MDNR Wildlife Division
            (517) 373-9418

THANKS for your help conducting this survey and have an enjoyable field season!