Richard L. Hoffman

Virginia Museum of Natural History

Martinsville, VA 24112

There is widespread, and justifiable, concern about the status of amphibian populations which appear to be decreasing in size or disappearing altogether, presumably in response to a variety of poorly understood environmental impacts.

In a purely local context, I have been witness to apparent attenuation of frog populations in western Virginia since about 1940 and take the opportunity to summarize the observations and conclusions accumulated during that half-century. The point must be emphasized that no quantitative bases for comparison may be cited, only subjective anecdotal interpretations. In 1940 it did not occur to me (then 13 years of age) to quantify my impressions about frog calls, nor would I have known how to even think about such an approach. Yet the memories are clear enough and may provide some insights into the course of then totally un-anticipatable events.

Yes, anurans have declined at many places in western Virginia. As a child I could assume that during the summer, toads gather in the circles of light at street corners in Clifton Forge, to forage on photo-drunk insects. This has not been true for a long time. During the 1950s, when I was preserving material for museum study purposes, it was possible to locate immense choruses of what was then called Pseudacris feriarum at many sites in Alleghany County. Now I would have difficulty in finding any.

In a broader context, the problem does not seem to be statewide. It is not difficult to find marshy fields full of P. feriarum not far from Martinsville, and on a rainy evening not long ago I drove backroads over much of Greensville County without ever being out of ear-shot of that species. The toads (Bufo woodhousii fowleri and B. americanus) do not seem to be in short supply in central and eastern Virginia; nor, for that matter, does the ubiquitous Pseudacris crucifer seem to have suffered reduced numbers.

I recently went back to Clifton Forge, Blacksburg, and some other places that used to be replete with treefrog choruses. At once some explanations suggested themselves from the vantage point of a time-remove. First and foremost is the pervasive effect of urbanization: marshes and ditches have been drained, filled, and built upon, on a large scale. Houses now stand, for instance, on the site of the only two breeding ponds once used by Scaphiopus holbrooki in Radford. Secondly is the effect of normal succession: many former marshy fields have turned into dry pine woods. Thirdly and probably most significantly, is the phenomenal increase in motor vehicles especially since the 1950s. Amphibians moving to a breeding pond usually do not hurry across roads, and the mortality inflicted on warm rainy spring nights is often appalling: one vehicle may take out literally hundreds of frogs before they get to water. After some years such heavy losses cannot but exert a real holocaustic effect on local breeding populations.

Of course all of these factors are operational statewide, but are far more concentrated in the Ridge and Valley Province, where flat land supporting lentic habitats is limited to narrow valleys in which the impact of development assumes a major magnitude. Wetlands are more dispersed and isolated in the Piedmont and even more so in the Coastal Plain, although anyone trying to recover roadkills on even remote backroads in these regions can attest to the frequency (and velocity) with which wide-track radials thunder past even long after midnight. It is surely an underestimation to believe that motor traffic is now 100 times greater than in 1935, in every part of the state.

An additional, although un-investigated, impact on frog populations, may be the effect of chemicals used to control highway ice and snow, much of which naturally drains into roadside ditches that used to be a favorite breeding site for Pseudacris feriarum in particular. Such ditches are also periodically gouged out by road grading machinery, busy at improving drainage.

"Acid rain" may indeed enter the picture as a detrimental factor, but hardly needs be invoked in the face of the obvious physical impacts noted above (nor, on the basis of subjective observations made at Mount Rogers since 1947, has it apparently reduced salamander populations). The combined effects of ongoing "development", natural succession, and logarithmic increases in vehicular traffic seem entirely adequate to account for dramatic declines which I have observed in parts of western Virginia during the past half-century.