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Abstract:  Amphibians have received increased attention in recent years from the scientific community and general public alike. Many populations throughout the world have declined, or even been extirpated, often without an apparent cause. Concern about the status of amphibians has translated into a growing interest in systematic and statistically sound monitoring programs. Several extensive efforts to monitor populations of calling amphibians are in place, and more are under development. Necessary for the design of appropriate surveys is an understanding of the behavior, especially vocalization, of the various species, and how it varies by geographic location and environmental conditions. In 1995 we conducted roadside surveys of calling amphibians along 44 routes in North Dakota. This report describes results of that survey, with special attention given to the variables that influence detectability of calling amphibians.

Key words:: amphibians, anurans, calling surveys, frogs, North Dakota, toads

Table of Contents

• Introduction
• Study Areas
• Methods
• Results and Discussion
• Conclusions and Recommendations
• Acknowledgments
• Literature Cited
• Table 1 -- Codes used for explanatory variables.
• Table 2 -- Number of transects and stations at which amphibians were recorded.

Distribution Maps

• Figure 1 - Plains Spadefoot Toad (Scaphiopus bombifrons)
• Figure 2 - Canadian Toad (Bufo hemiophrys)
• Figure 3 - Woodhouse's Toad (Bufo woodhousii)
• Figure 4 - Great Plains Toad (Bufo cognatus)
• Figure 5 - Gray Treefrog (Hyla versicolor)
• Figure 6 - Western Chorus Frog (Pseudacris triseriata)
• Figure 7 - Northern Leopard Frog (Rana pipiens)
• Figure 8 - Wood Frog (Rana sylvatica)

Study Factors

• Figure 9 - Date
• Figure 10 - Time of Night
• Figure 11 - Temperature
• Figure 12 - Humidity
• Figure 13 - Precipitation
• Figure 14 - Wind
• Figure 15 - Cloud Cover
• Figure 16 - Moonlight