82 
Heather J. Kalb and George R. Zug 
5 
4 
1 
200 300 400 500 
MSG Diameter (jn m) 
Fig. 1. The relationship between MSG (marks of skeletal growth) diameters 
and age in Bufo americanus from Eakin Park, Fairfax Co., Va. 
number of MSGs lost (i.e. 0, 1, or 2 years in this data set). Because a 
LAG forms each winter and periosteal growth begins anew each spring, 
we accept the hatching of tadpoles as age 0 and each subsequent spring 
as a “birthdate”; therefore a toad with two MSGs and captured in 
spring 1988 hatched and metamorphosed in 1986. 
Population structure. The following interpretations are based on 
the total of the number of MSGs seen and the number of MSGs 
estimated to have been lost. In 1983, Zug marked 19 adult toads; age 
estimates are available for 16 toads. Males ranged from 2 to 4 years and 
females from 4 to 5 years (Fig. 2). In 1984, 53 adults were seen, 41 
marked, and ages estimated for 31; the age range is the same as for 1983 
toads. Fifteen toads were seen and marked in 1985; ages estimated for 
14 with a similar age distribution as in 1983-84. 
Estimated age and body size. There is no significant correlation 
between age and body size (snout-vent length; SVL). In males (N = 46), 
the correlation coefficient is low (r = 0.20, P> 0.05), and when all toads 
with estimated age (N = 61) are examined, the correlation is marginally 
better (r = 0.45, P < 0.01). In contrast, the correlation (r = 0.92) is 
significant for the association of weight and length (wt = -103.89 + 2.08 
SVL) for all toads captured. 
Age and size in amplectic toads. Since all males captured were 
calling and the females were moving toward the male choruses or in 
