Download Michigan Frog Survey Update December 2001 Watch your timing

Michigan Department of Natural Resources
Wildlife Division
Natural Heritage Program
Michigan Frog Survey Update
December 2001
only 1 or 2 at each site, you’re too late. If you’re
doing your 2nd run and hearing only green frogs
and an occasional gray treefrog, you’re too late.
Wood frogs will be missed if you’re out past the
2nd week of April in the Lower Peninsula. They’ll
usually call for about a week later in the Upper
Peninsula.
You might even be hearing the right species at
the right time, but think about the abundance in
which you’re hearing them. The focus of your
survey should be to be out there, listening, when
the various species are calling at their peak, which
is going to be the result of perfect calling weather
and timing. We don’t want to just try to be out
there when there’s still a few calling, we want to
listen when they’re calling in frenzied proportions,
at the peak of the breeding season. In order to do
that, not only does the weather have to be right, but
timing is a factor too.
Another timing issue results when you do your
runs too close together. The instructions say to
make sure you wait at least two weeks between
runs. Longer than two weeks is even better. The
more your runs are distributed throughout the
spring months, the more species you’ll hear and
you will be reporting a more realistic picture of
what is happening in your area. If runs are too
close together you will probably be reporting much
the same species in both runs.
Watch your timing
Just a few reminders to keep everyone on the
same page when we’re out there listening to frogs
in the springtime. Even though this past spring
was not unusually cool or warm, for some reason,
many volunteers ran their routes really late.
In the past, you’ve been urged to pay more
attention to temperature and weather conditions
than to date because weather is what frogs respond
to. Well, this is still true, but there are limits to
weather impacts when frog calling starts and ends.
Each species only calls for so many days a year,
weather permitting. If they’ve been calling for say,
a month, no matter what the weather is, their
breeding season may have run its course.
Even though temperatures may be unseasonal,
either too warm or too cool, survey results will be
compromised if you wait too long for those
temperatures to be just right.
I am enclosing an updated version of the frog
survey instructions with this update that
contains new information on timing of surveys.
Basically, the rule of frog call surveying in
Michigan is as follows:
1st run: April
2nd run: May
3rd run: June
Mink Frogs
Herpetologists in the Great Lakes region
believe the mink frog is declining. For those
observers that have survey routes within this
species’ range (i.e. the Upper Peninsula) please be
on the lookout. This species is known to call in the
wee hours of the morning so you have to be
diligent to hear these guys most years. Please try
to make the effort to hear this species on your
route.
Zone 1 may start as early as the last half of
March and Zones 3 & 4 may go as late as the first
half of July, depending on weather conditions.
Please do not run your route too late – or too
early. If you’re in Oakland County, for example,
and you have not had a chance to do your 3rd run
and its July, don’t bother running it. But, please
send in your 1st and 2nd run results.
There are indicators that you are running your
route too late. For example, if you’re out on your
3rd run and hearing predominantly green frogs and
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The Michigan Frog and Toad Survey:
A Five-Year Summary of a Successful
Monitoring Program
Observer Study
A big THANK YOU to all of those who
completed and sent in their observer survey
questionnaires and sample routes!!
By Kristen Genet, Dept. of Zoology,
Michigan State University
Herp Atlas Update
The Herp Atlas Handbook is now available!
All active Frog Survey volunteers were
automatically sent a manual. If you didn’t get one,
let me know.
The Michigan Frog and Toad Survey was
initiated in 1996 and has been organized through the
Natural Heritage Program in the Wildlife Division of the
MI DNR. With any monitoring program, there is so
much annual variability that it is imperative that multiple
years of data are collected before that data can be
analyzed to look for patterns of distribution and
abundance in space or time. We now have six years of
data (1996-2001), and this summary represents an
analysis of the first five years (1996-2000). Even though
we now have data from a number of years, it is likely not
enough to accurately depict trends of frog and toad
abundance in Michigan. At least ten and preferably 15
or 20 years of data collection will be necessary for a
comprehensive look at what is happening to our frogs
and toads. The objectives of this project were to: (1)
evaluate the status of anuran populations in southern
Michigan using the first five years of data collected in
the Michigan DNR Frog and Toad Survey, (2) determine
short-term trends and data needs for future monitoring
efforts in Michigan, (3) project abundance of species
over the next few decades and to their stable abundance
distributions, and (4) evaluate potential biases in the
dataset due to diverse volunteer backgrounds.
Validation of Calls
Please remember to send in a recording or
other type of validation of Cope’s gray treefrogs
and Blanchards’s cricket frogs the first time you
hear them. The Cope’s gray treefrog’s call is easy
to misinterpret and the cricket frog is a species of
special concern so we want to be sure you’re
hearing what you think you hear. Once you have
confirmed a call, you do not have to confirm it if
you hear the call again in subsequent years. If you
consider yourself knowledgeable enough to
identify these species without validation, please
contact me and I’ll make sure I have that on record.
Michigan Joins National Frog Survey
The 2001 survey year was the first year that
the national survey protocols are implemented.
Through NAAMP (North American Amphibian
Monitoring Program) the US Geological Survey
(USGS) office in Patuxent, Maryland have, with
the help of state frog survey coordinators,
developed frog survey protocols that will be used
across the country. Similar to the Breeding Bird
Surveys, also coordinated by the USGS in
Patuxent, the protocols will help to standardize the
way frog surveys are done so that the data we get
can be compared between states and between
regions.
Only NAAMP routes that were computer
generated by the USGS folks can be included in
the national study, however. Observers with
NAAMP routes will be able to enter data online so
that it goes directly to NAAMP. If you’re
interested in doing a NAAMP route, please contact
me. Routes are statewide but not in every county.
NAAMP protocols are slightly different than what
we’ve been doing here in Michigan. Those
running non-NAAMP routes need to keep doing
their routes as they have in the past.
1999
2000
1998
1997
70%
1996
Figure 1: Year Route Initiated
Statewide, there are a total of 227 routes, and most of
those are concentrated in the southern lower peninsula.
Each of these routes consists of 10 sites, which are
surveyed three times each spring, corresponding to the
phenology of the early, middle, and late spring breeding
frogs and toads. Most of these routes were established
in 1996, when the monitoring program was also started,
although new routes are added each year (Fig. 1). Of
these routes, more than half of them have been surveyed
for three or more years, which is crucial for detecting
long-term trends in abundance and distribution (Fig. 2).
2
5
1
4
5
32%
Number of Species
24%
14%
16%
14%
2
3
1996
1997
4.5
1998
4
1999
2000
3.5
3
2.5
Vernal
Pond
Figure. 2 Number of Years Route Surveyed
Wet
Meadow
Bog or
Fen
Marsh
Wooded
Swamp
Pond
Other
Wetland Type
Figure 3: Mean number of frog and toad species in
Volunteer commitment to survey the same route for a
sequence of several years is very important to the
success of a monitoring program. Other states have
similar monitoring programs, and the Wisconsin Frog
and Toad Survey reports that their average volunteer
participates in their program for eight years. We are in
the process of surveying volunteer opinions and their
estimated commitment to this monitoring program, and it
seems that in general, volunteers plan to survey their
routes as long as they are living in the area and are able.
For this summary, the methods used included:
(1) evaluate changes in abundance and site occupancy
over the five-year period with linear regression analyses
(Eastern gray treefrogs and Cope’s gray treefrogs were
combined for this analysis), (2) the analyses were
performed only on sites that have been surveyed for all
five years (585 sites representing 59 routes), (3)
abundance was calculated and projected into the future
using modified transition matrix models, and (4) a
standardized questionnaire and frog and toad call
recordings were sent to volunteers to evaluate the
influence of volunteer background and experience and
to assess the usefulness of the current protocols.
Statewide, there seems to be a decrease in the number of
species found in different wetland types (Fig. 3). The
change in the number of species in bogs/fens and
wooded swamps was not statistically significant, but the
other wetland types showed a significant decline in the
mean number of species found there from 1996-2000.
This could be a result of either a real decrease in species
richness in these sites or the sites becoming
inappropriate for amphibian breeding. For example,
with a warm spring and less rain as we’ve seen in recent
years, fewer vernal ponds are filling with enough water
to support amphibian breeding.
Four species are found at more than 50% of all
sites; those species include spring peepers, gray
treefrogs, green frogs, and western chorus frogs. The
remaining seven species were found at less than 50% of
the sites surveyed. Three species (gray treefrogs,
leopard frogs,
different wetland types
and Fowler’s toads) declined in the proportion of sites
occupied over the five-year period, while bullfrogs
showed a slight increase in the proportion of sites they
were found calling in (Fig. 4). The number of sites
where gray treefrogs were heard calling in highest
abundance (call index of 3) declined from 1996-2001,
while the number of sites where this species was absent
increased over the same time period. Similarly, the
number of sites where leopard frogs were heard calling
in intermediate abundance (call index of 2) declined
while the number of sites where this species was absent
increased. For bullfrogs, the number of sites where they
were absent declined, and the number of sites with a few
individuals calling (call index of 1) increased.
What do these short-term trends mean for longterm population persistence? To answer that question, I
used modified matrix population models to project
future abundance based on changes in abundance that
happened between 1996-2000. Matrix models describe
changes from one time period to the next based on a set
time interval (five years, in this case). Repeated
projections of the model provide an indication of longterm population dynamics. The results showed that two
species that are abundant and widespread (spring
peepers and gray treefrogs) may show an increase in the
number of sites where they are absent while the number
of sites where these species call in full chorus (call index
of 3) decreases (Fig. 5). Very little change in abundance
was seen for the other species, which indicates that
based on the first five years of data we have collected,
most species will remain at levels that we currently are
observing. Three species were present at too few sites to
make accurate predictions with these models
(Blanchard’s cricket frogs, pickerel frogs, and Fowler’s
toads).
We are in the process of evaluating the current
protocols and call indices used as well as the influence
of volunteer background and experience on the data that
are collected. Typically in a scientific study, data are
collected by one or a few individuals to control for
differences among observers. In the Michigan Frog and
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Toad survey, hundreds of volunteer observers send in
data each year. To assess any potential biases in the
dataset due to differences among volunteer observers,
we sent out a questionnaire and standardized recording
of frog and toad calls to all of the volunteers who have
recently contributed data to the Frog and Toad survey.
We are currently in the process of analyzing that data,
and we hope to determine whether (and which) species
are consistently missed, misidentified, overestimated, or
underestimated. We also intend to determine whether
the current call indices that we are using are useful and
assigned similarly by our diverse volunteers.
In summary, trends over the past five years
suggest that anurans in southern Michigan may be
suffering some declines in abundance and/or
distribution. Long-term monitoring and continual data
collection is essential for tracking changes in these
amphibian communities. Short-term changes in site
occupancy and abundance may lead to long-term
changes in anuran communities in this area. Some of the
more uncommon species (i.e., Cope’s gray treefrog,
pickerel frog, Blanchard’s cricket frog) deserve
additional detailed studies and their occurrence at survey
sites should be verified. In terms of the future of the
Michigan Frog and Toad Survey, the number of new
recruits and retention of established volunteers in the
program are both high. Participation in training and
refresher workshops held earlier this year was also high.
The value of this dataset increases as each additional
year is added, so we hope that the first five years is a
good indication of the level of participation we will see
for the duration of the monitoring program.
Michigan Frog and Toad Survey Web Page:
http://www.dnr.state.mi.us/Wildlife.asp?linkid
=72&Link=link&imageID=
NAAMP Web Page:
http://www.mp1-pwrc.usgs.gov/amphib/sitemap.html
Survey Coordinator:
Lori Sargent
DNR Wildlife Division
P.O. Box 30180
Lansing, MI 48909
(517) 373-9418
Fax: (517) 373-6705
E-Mail: [email protected]
The Michigan Department of Natural Resources (DNR) provides equal opportunities for employment and for
access to Michigan natural resources. State and/or Federal laws prohibit discrimination on the basis of race,
color, sex, national origin, religion, disability, age, marital status, height and weight. If you believe that you
have been discriminated against in any program, activity, or facility, please write the DNR Equal Opportunity
Office, PO Box 30028, Lansing, MI 48909-7528, or the Michigan Department of Civil Rights, 1200 6th
Avenue, Detroit, MI 48226, or the Office of Human Resources, US Fish and Wildlife Service, Washington, DC
20240. For additional information or assistance on this publication, contact DNR, Wildlife Division, PO Box
30180, Lansing, MI 48909.
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