Photographic Technique 
133 
Fig. 2. Quadrat B showing the meter rule and the 25 x 40 cm study plot. 
RESULTS AND DISCUSSION 
Results of the photographic overlays are provided in Fig. 3. Tadpoles 
were easily counted and marked; seldom was there a question as to 
whether a black mark on the photograph should be counted. However, 
tadpole shadows are a potential problem. Densities of tadpoles were 
generally D-2 (20-50% of area covered by tadpoles, tadpoles within 1-5 
cm of one another) or D-3 (51-89% of area covered, tadpoles mostly in 
contact) in the sense of Beiswenger (1975); if densities greater than this 
are encountered, photographic analysis might prove difficult. 
Although the five study plots were apparently selected at random, I 
made no attempt at complete objectivity, such as using a table of random 
numbers to preselect quadrats. Therefore, an estimate of population size 
based on total numbers of tadpoles from these sites would not provide a 
statistically accurate picture of tadpole numbers. Methods for the estima- 
tion of population sizes via direct counts within randomly selected 
quadrats are available. Caughley (1977) provided several methods which 
might be useful, notably the use of stratified random sampling as applied 
to aerial surveys. 
