State of the Greater Fundy Ecosystem

GREATER FUNDY ECOSYSTEM RESEARCH PROJECT

UNB Faculty of Forestry and Environmental Management

State of the Greater Fundy Ecosystem

Assessing Acoustical Monitoring
of Frogs and Toads
in Atlantic Canada

Kerri Oseen and Richard Wassersug
Dept. of Biology and Anatomy and Neurobiology
Dalhousie University
Halifax, N.S. B3H 4J1

A study was initiated to test the feasibility of using automated recorders to monitor anuran (frog and toad) populations in Atlantic Canada, and to determine the effects of environmental conditions on the breeding activity of these same populations. Our study was predicated on the fact that anurans produce advertisement (mating) calls during the breeding season, and these calls can be used to determine: 1) the timing and duration of the breeding season; 2) the stability of the breeding population over the long-term; and 3) the approximate size of the breeding population. Factors, such as temperature and barometric pressure, are known to influence calling activity, and were concurrently recorded.

Acoustical monitoring with automated recorders began in the summer of 1996 in four Atlantic region National Parks: Cape Breton Highlands and Kejimkujik National Parks in Nova Scotia; Kouchibouguac and Fundy National Parks (FNP) in New Brunswick. In 1997, only sites in Kouchibouguac and FNP were surveyed. All sites sampled in 1996 were permanent or semi-permanent, and included lakes, bogs, ponds and brooks. Sites sampled in 1997 were permanent ponds, with four out of the five having beaver activity.

GOALS

Specific goals of this project were:

To determine the feasibility of using automated recorders to monitor anuran populations over the long-term.
To adapt, if possible, automated recording devices developed in South Carolina to the wet, cool climate of Maritime Canada.
To determine the calling activity patterns of amphibians and the influence of environmental parameters, such as temperature and barometric pressure, time of day, etc. on calling activity of anurans.
To assess whether or not volunteers would be able to continue the project in the future.

METHODS

Anuran advertisement calls were recorded using automated recording devices developed by Mike Dorcas and Charles Peterson at the Savannah River Ecology Laboratory in South Carolina. These recorders utilize a timer to automatically activate a tape recorder at pre-set intervals for specified durations. The unit consists of a stereo tape recorder, microphone, recycling timers, 12-V power supply, and a voice clock. All components except the microphone are housed inside a weather-resistant toolbox.

In 1996, an acoustical sampling interval of 12 seconds every 15 minutes, every second hour was used. Sampling was conducted from early May until the end of August. In 1997, this sampling regime was changed to one minute every hour, from early May until late August.

The summer of 1996 was used primarily for testing the sampling protocol and surveying different types of habitat. Two recorders were placed at each park. One was stationary at a single site for the entire season, while the other recorder "roved" between three sites on a four-day rotation (Fundy had two "roving" recorders). All sites sampled in 1997 had stationary recorders.

In addition to recording vocalizations, several weather variables were automatically recorded. Hourly measurements of water and air temperature and relative humidity were obtained using automated dataloggers from early May until late August. Hourly measurements of barometric pressure, precipitation, wind velocity and direction, and cloud cover were obtained from weather stations located in each park.

RESULTS

A preliminary look at the calling activity of anuran amphibians at a single site, Whitetail Pond in FNP, in 1996 follows. Further analysis will correlate calling activity with the environmental variables measured.

Five anuran species were recorded at Whitetail Pond in 1996: Wood Frogs, Spring Peepers, American Toads, Green Frogs, and Bullfrogs (Figure 1). Wood Frogs and Spring Peepers were the earliest spring breeders, and were recorded from the first of May, although personal observations indicated that they had begun to call during the warmer parts of the day in late April. Wood Frogs were only recorded from May 1-2 and 14-15. How this disjunct pattern is related to the weather conditions at that time is not yet known. Spring Peepers called steadily from the first of May until July 8.

Figure 1.
Calling activityof anuran amphibians in Whitetail Pond, FNP, in 1996. Julian day 120
corresponds to April 29, day 183 to July 1, and day 220 to August 7. Also shown as
the solid line is the 45 year mean (1950 - 1995) maximum air temperature.

American Toads were the next species to begin calling, commencing around May 8. Toads called periodically at first, and then steadily until June 17.

Bullfrogs and Green Frogs began calling in the middle of June. Green Frogs called fairly steadily from June 13 to August 8, while Bullfrogs were only recorded periodically in June (June 16, 30) and July (July 1-5).

A young Green Frog
(Photo: M. Rosen/FNP)

Statistical tests for correlations between the recorded calling activity from 1996 and 1997 and the environmental variables measured will be analyzed next. This should yield information on how amphibians are influenced by abiotic environmental conditions during the breeding season, and whether or not their response to a given variable changes over the breeding season.

Implications for Management

It is believed that amphibian populations are declining globally; however, without baseline monitoring data of populations within Atlantic Canada, the stability of our amphibian populations can not be assessed. Monitoring projects, like this one, have the potential to provide us with the necessary baseline information.

The key to the continuation of this project will be volunteer participation. At the present time, volunteer groups and interested individuals are being contacted and trials of the project set up. Feedback regarding the feasibility of volunteer groups, working with automated recorders to monitor amphibians, is necessary in order to determine the future direction of the project.

ACKNOWLEDGMENTS

We would like to thank the many people who have provided valuable assistance with this project: Douglas Clay, Eric Tremblay, James Bridgland, Cliff Drysdale, Marc Mazerolle, George Sinclair, Sedgewick Sinclair, Thane Watts, Rick Cook, Julie Page, Shannon Oseen, and last but not least, Joanna Blair. Thanks also to Parks Canada and Environment Canada for funding this project.

Further Reading:

Clay, D. and J. Brownlie. 1996. Status of amphibians and reptiles of Fundy National Park and its greater ecosystem. In: D. Clay (ed.) Resources of Fundy National Park: A primer of ecosystem studies. Part II. Chapter I. Pks. Can. Eco. Sci. Rev. Rept. No.2. 38 pp.

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