Date of Award

Fall 1997

Project Type


Program or Major


Degree Name

Doctor of Philosophy

First Advisor

James T Taylor


The purpose of this study was to investigate if mating success and clutch size are good estimates of reproductive success in a population of Bufo americanus, through the study of the contribution of life history parameters to the variation in individual reproductive success. A B. americanus population that breeds in a pond located in Madbury, NH was studied during the 1994, 1995 and 1996 mating seasons. In 1995 and 1996 clutches were also studied and the larvae were used in laboratory and field experiments. The following fitness parameters were investigated: mating success, clutch and egg size, growth rate and survivorship of the larvae, time to metamorphosis, proportion of larvae that completed metamorphosis, and body size at metamorphosis.

The results of this study suggest that male mating success was not size dependent in any of the three mating seasons studied. However, size assortative mating found in 1995 is an indication that male body size may represent an advantage in reproductive success, and consequently be subject to selection, because larger males may father a larger number of offspring due to the positive correlation between female body size and clutch size.

The influence of male and female body size on reproductive success was limited to effects on the number of eggs produced (females) or fertilized (males), as variation in the other fitness parameters could not be related to variation in the size of parents. Variation in the larvae in the fitness parameters studied was also not significantly related to variation in number of offspring or mean size of eggs in the clutches.

Experimental results suggest that variation in food and density levels affect larval growth and survival, as increase in food level and decrease in initial density had a positive effect on larvae size and survivorship, and on the percent of larvae that complete metamorphosis.