Ten Years of Counting the Ribbits
In the words of that famous amphibian Kermit, "It's not easy being green."
Over the past 25 years, scientists have been concerned about declines and/or population die-offs of several amphibian species worldwide. 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.
There are 11 species of frogs and two species of toads generally present in Michigan. In order to address the amphibian decline issue in this state and to begin monitoring their populations a statewide volunteer calling survey was initiated in 1996 by the Department of Natural Resources' Natural Heritage Program.
"Amphibians generally do not receive the attention given to the larger, more attractive animals," said Raymond Rustem, supervisor of the Natural Heritage Unit. "Most people do not know the sounds they make or how to distinguish these sounds from those made by songbirds. By the time most people may notice a decline in their populations, frogs and toads may be almost non-existent."
Initially, Michigan's survey protocols mirrored that of the successful and long-running survey in Wisconsin. Later, the U.S. Geological Survey developed nationwide protocols as part of the North American Amphibian Monitoring Program.
Survey routes consist of 10 sites at which volunteers stop and listen for frogs and record the species and an abundance index for each species on a data sheet. Surveys are conducted in the evening, when more amphibians are active. Each survey route is visited three times during the breeding season.
Nearly 500 survey routes were registered throughout Michigan during the first two years.
"The initial surveys provided information on where the different species of frogs and toads are in the state and how many there are," Rustem said, "but we also wanted to identify areas where declines were significant and we hoped the volunteers could collect enough data over time to help us determine the causes of those declines."
Since the annual frog and toad survey began, data has been submitted from all 83 Michigan counties, with an average of nearly 250 survey routes reporting each year. There are 96 routes that have submitted data all 10 years.
According to Lori Sargent, who has been the survey coordinator from the beginning, the survey has confirmed that we have stable populations for most species, but long-term trends require many years of data before significant and meaningful information can be calculated.
"Scientists know that natural fluctuations occur in amphibian populations, but the exact intervals of those cycles remain unknown," Sargent said. "Many years of data are necessary to be able to distinguish these fluctuations from those caused by man-made factors, such as impacts of pesticides or habitat losses."
Weather factors also play an important role in calling surveys and can affect the amount and the quality of the data in any one year, she said.
Although some of the volunteers are professional biologists and herpetologists, thousands of interested citizens, including entire school classrooms, have participated in the survey.
"New volunteers always are welcome and needed, especially those people who can participate for several years," Sargent said. "Help is particularly needed in the eastern Upper Peninsula where we hoping to learn more about the status of mink frogs, a species found only in the U.P."
To show their appreciation to all the volunteers who have generously donated their time and skills since 1996, the DNR is hosting a Michigan Frog and Toad Survey 10th Anniversary Celebration Dec. 13 at the Amway Grand Plaza Hotel in Grand Rapids. The reception begins at 6 p.m. and follows a special symposium on amphibians, which is part of the Midwest Fish and Wildlife Conference.
An earlier reception, attended by more than 75 volunteers, was held last month at the National Amphibian Conservation Center at the Detroit Zoo.
"These events allow us to publicly acknowledge those dedicated individuals who are 10-year veterans and who are helping this project maintain a consistent and knowledgeable volunteer workforce," Sargent said.
The Michigan Frog and Toad Survey is funded by voluntary donations to the Nongame Wildlife Fund. Individuals can help by making a $10 donation online at www.michigan.gov/michiganestore. Click on "Tax Deductible Donations," then click on the loon. Add to shopping cart and follow the normal check-out process. Or mail a donation to the Nongame Wildlife Fund, P.O. Box 30180, Lansing, MI 48909. All donations are tax deductible on your federal tax form.
For more information on how to get involved in Michigan's annual frog and toad survey next spring, contact Lori Sargent at the DNR Wildlife Division, Box 30180 Lansing, MI 48909 or e-mail at [email protected] Information about the survey also may be found on the DNR Web site at www.michigan.gov/dnr. Go to Wildlife and Habitat and then click on Research Projects.
• Frogs call for much the same reason birds sing in the springtime -- to attract mates and establish territories. Some species, such as the northern spring peeper, will start calling at the first sign of warm weather. In southern lower Michigan, in an average year, the spring peeper usually begins calling during the last week of March or the first week of April.
• Collectively, frogs and toads are a group of amphibians called "anurans," which means "without a tail." Frogs have smoother skin, longer legs and spend more time in the water than toads. Toads generally take short hops while frogs may leap several feet in one jump. In Michigan the bullfrog is found throughout the Lower Peninsula and in parts of the Upper Peninsula