Tolerance of Acidity in a Virginia Population of the 
Spotted Salamander, Ambystoma maculatum 
(Amphibia: Ambystomatidae) 
Charles R. Blem and Leann B. Blem 
Virginia Commonwealth University, Department of Biology, 
Academic Division, Richmond, Virginia 23284 
ABSTRACT . — We investigated apparent acid tolerance of egg masses 
of the spotted salamander, Ambystoma maculatum , in the lower 
piedmont and coastal plain of Virginia. All temporary ponds that we 
tested in east-central Virginia were acidic (i.e., pH < 6.0), and the 
majority (about 93%) had no ambystomatid egg masses in them during 
the spring breeding season. However, a few ponds continued to 
support successful spotted salamander populations, even though their 
pH levels were below those that caused extensive mortality of eggs and 
larvae in the laboratory. In laboratory tests, more than 50% of the eggs 
removed from these ponds survived pH levels of 4.3 to 4.7, but no eggs 
or larvae tolerated experimental exposure to a pH less than 4.0. Local 
tolerance of low pH may result from natural selection of resistant 
individuals through long exposure to the acidic, hoggish waters of the 
coastal plain and lower piedmont. However, we hypothesize that 
aluminum may be involved in apparent resistance to low pH. Some 
coastal plain and piedmont soils are low in aluminum, and large 
amounts of organic materials may bind and inactivate the aluminum 
that is present. Lowered levels of dissolved aluminum may permit 
survival of salamander embryos/ larvae at a low pH. This hypothesis is 
supported by increased mortality of embryos in test containers to 
which small (< 0.3 ppm) amounts of aluminum were added. Soils and 
temporary ponds of the lower piedmont and coastal plain of Virginia 
are naturally acidic and have little buffering capacity. Future 
acidification of the environment as a result of acid precipitation is 
likely in this region. Our tests indicate that slight decreases in pH of 
temporary ponds may result in eradication of the spotted salamander 
from this part of Virginia. 
Tolerance of low pH by amphibians recently has received much 
attention (for a review, see Pierce 1985). In general, most adult 
amphibians are relatively tolerant of acidity or conditions associated 
with low pH, but eggs and larvae may suffer extreme mortality under 
mildly acidic conditions (Saber and Dunson 1978, Dunson and Connell 
1982). Eggs and larvae of the spotted salamander, Ambystoma 
maculatum , seem to be especially sensitive to low pH, and the species 
may be decreasing in number at some locations because of acidification 
of breeding ponds resulting from deposition of atmospheric acid (i.e., 
acid rain; see Pough 1976, Pough and Wilson 1977). 
Brimleyana No. 15:37-45, January 1989 
37 
