Frog and Toad Calling Survey 2001
The NAAMP's Frog and Toad Calling Surveys are highlighted in this year's
of the World 2001
book, a yearly report submitted by the Worldwatch Institute's research
Minnesota is exemplified in particular for its "well-tuned"
Would you like to get involved in surveying frogs and toads
in Minnesota? Scientists and herpetologists would like to get a more precise
idea of the numbers of each frog and toad species in the state. This will
enable them to look at population densities over time and determine whether
populations of specific species are declining or increasing on a local
and state-wide basis.
AND TOAD SURVEY INSTRUCTIONS
Background and Purpose:
In recent years, many observers have been concerned not only with
the decline of global amphibian populations, but also with changes in
frog and toad populations around the United States. Scientists worldwide
are concerned about these declines because amphibians are shown to act
as bio-indicators of environmental health. In 1991, scientists from every
continent volunteered to be part of the Declining Amphibian Populations
Task Force (DAPTF). "Established in 1991, the DAPTF consists of a network
of over 3,000 scientists and conservationists belonging to national and
regional working groups which now cover more than 90 countries around
the world. The purpose of the DAPTF is to determine the nature, extent
and causes of declines of amphibians throughout the world, and to promote
means by which declines can be halted or reversed" (http://www.im.nbs.gov/amphibs.html).
The North American Amphibian
Monitoring Program (NAAMP), the North American component of DAPTF,
developed a set of standards to help monitor amphibian populations around
the United States. The standards were further developed into monitoring
programs, including the frog and toad calling survey. The NAAMP frog calling
survey is an international effort to track the health of frog populations
in Canada, the United States, and hopefully soon in Mexico. For more information
on the NAAMP, please visit their web site at: http://www.im.nbs.gov/amphibs.html
The Minnesota Frog and Toad Calling Survey was initiated to increase
the knowledge of the abundance and distribution of the fourteen
frog and toad species, and to monitor population changes in the state.
The NAAMP has developed a series of pre-established routes that include
a variety of habitats, such as wetlands, forests and grasslands. Each
route consists of ten wetland (breeding) sites, which are visited three
times annually (early spring, late spring, and summer) by volunteer observers.
At each site, the observer identifies the species present on the basis
of breeding season calls and makes a simple estimate of the abundance
of each species using "call index" values of 1, 2, or 3.
Establishing a New Survey Route
When you receive a new route that has never been surveyed, it must
be tested before the first survey is made. First, locate the route on
a map (shown below) and drive to its starting point. As you drive along
the route look around for potential amphibian breeding sites. The sites
should be no more than 200 meters off-road and may include areas such
as ponds, shallow wetlands, streams, and roadside ditches. Try to include
a variety of wetland types that represent the range of breeding sites
available for the various species in the area. Consider large and small
ponds; open, shrubby and wooded areas; stagnant and flowing streams; and
agricultural and urban sites. Do not avoid ponds that dry up during the
year, for they are often productive during the spring. Do avoid swift
moving streams, and deep or denuded shores of lakes. Designate ten sites
that are located at least 0.5 miles from each other. The ten sites become
permanent stops on the route and will be used in each of the three survey
Click on map to see larger version.
Surveyors 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 necessary to replace the problem site with a new site sometime after
the first survey run. To avoid this, it is recommended that you begin
with eleven or twelve sites for the first year and choose the ten most
reliable sites for the permanent route. At the end of the first year,
report results only for the ten permanent sites.
If you come to the end of your route without placing all ten stops, then
simply continue driving in the direction indicated until all ten have
been determined. While busy looking for sites, it is also important to
make sure that the roads are appropriate for stopping along. If they are
too busy, too dangerous, on private land, or poorly maintained, the routes
may be shifted to the nearest set of appropriate roads that travel in
the same direction. Please make note of any changes or discrepancies on
the maps and datasheets provided.
Describe your route. Mark the precise locations of your ten sites
on the assigned maps, and describe each listening point and wetland on
the "survey route description" form. Sites should be numbered in a convenient
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.
A NEW OR ESTABLISHED ROUTE
1. Obtain and review instructional materials
and data forms.
The main, designated surveyor for each route should automatically receive
these materials in late March or early April. Contact the coordinator
if you have not received your packet by April 7th.
Materials include: Instruction package, Sample form package, Route
maps, Survey route description form, Field data sheet, Dashboard card,
'Toads and Frogs of MN and Their Habitats'
poster, 'Call of Minnesota's Frogs
and Toads' cassette tape (given to new surveyors).
2. Know the calls, phenology,
and general ranges of Minnesota frogs and toads.
New and experienced observers will find it helpful
to review the 'Calls of Minnesota's Frogs and Toads' cassette 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, Northern
Leopard Frog, Western Chorus Frog, and Pickerel Frog) followed
by those species that begin calling in late spring
(the three toads, Northern Cricket Frogs and both
treefrogs), and finally by those species that begin to call 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. Generalized species distribution maps are attached. Additional
information on frog and toad natural history is available in Amphibians
and Reptiles Native to Minnesota by Oldfield and Moriarty. This book
should be available at your local library or call 651-523-2945 for more
3. Run the route 3 times, once
during each designated period.
The timing of the survey with the phenology of frog calling is
essential. Data collected from outside the designated survey periods is
difficult to interpret and impossible to compare between years or areas.
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. In addition, consider minimum water temperatures, especially for
the early spring survey period. The dates of the first survey run may
be variable due to the differences in snowmelt in northern and southern
||Range of Dates
||Minimum water temperature
||May 20-June 5
||June 25-July 10
*Routes north of Highway 2 can add one week to the survey dates.
4. Run surveys after dark, under
Choose an evening when water temperatures are above the minimums
statewide and when wind is less than 8 mph. Warm, cloudy evenings with
little or no wind and high humidity (even drizzly) 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 soonest opportunity (within 2?3 days if possible).
Please make note of these conditions.
5. Listen for calls at each site.
Approach a listening point so as to cause minimal disturbance. The arrival
of a car or a person on foot may cause frogs to stop calling for a short
time. When the frogs start calling again, listen for five
minutes. Listen to all calls audible from your listening point, not just
those emanating from a particular pond or side of the road. Some calls
may be drowned out by other calls, 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 making a loud noise with the car horn, door or by voice.
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. A sound parabola
is helpful in isolating subtle calls of individuals in a chorus of several
species. Prescription hearing aids are helpful for listeners who have
volume or frequency impairment.
6. Record your observations on
the field data sheet.
Completely fill out the Minnesota Frog and Toad Survey route data
sheet including county, route number, date, observers names and addresses,
weather conditions, water temperature (if taken), time, changes in habitat
since previous visits, and additional comments on noise levels, such as
attempts to silence loud choruses. Record the call index value for each
species heard according to the following:
1: Individuals can be counted with space between calls,
2: Calls of individuals can be distinguished but there is some overlapping
of calls, or
3: Full chorus. Calls are constant, continuous, and overlapping.
7. Verify records of rare or
Verification is required for Cricket Frogs and for records of other
species found outside their previously documented range as indicated by
the attached range maps. Verification can be accomplished by: a) a tape
recording, b) testimony of two experienced observers, c) a photo, or d)
a specimen. After an observer has verified the record, future records
of the particular species in that area may not be required.
8. Return all materials by 1
September MNDNR Nongame Research.
9. 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 alternates should accompany you on the survey periodically
and be familiar with the calls, route, and procedure.
For more information on Minnesota
Frogs and Toads click here.
An audio-tape or CD of Minnesota Frogs and Toads Calls is available from
the project at a cost of $12, which covers tax, shipping and handing.
If you are interested in this tape, please send a check to Hamline University
CGEE, MS-A1760, 1536 Hewitt Ave., St. Paul, MN 55104-1284. Make the check
payable to Hamline University.
Barney Oldfield and John J. Moriarty produced a book entitled
Amphibians and Reptiles Native to Minnesota (1994), which is available
from the project. This excellent guide to the state's herps is invaluable
to anyone interested in this topic and these animals.
This web site had been made possible by the generous support of various
federal and state agencies, as well as private foundations and donation.
Click here to see a list of the organizations
whose donations have made this web site possible.
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